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Suggested Short Title

NUTRITIONAL ASPECTS OF DAIRY CATTLE INFERTILITY

M. Sc.

ABSTRACT

NUTRITIONAL ASPECTS OF DAIRY CATTLE INFERTILITY IN QUEBEC AND TRINIDAD

Hezekiah H. Nelson Animal Science Nutrition

Eleven dairy herds from Quebec, thirty herds from

Trinidad, plus a Trinidad Government Holstein herd and

Crossbred herd were surveyed to de termine factors, mainly

nutritional, affecting fertility. Mean services per

conception were 2.1, 2.2, 3.0 and 2.7; and mean calving

intervals were 399, 437, 488 and 435 days respectively. Two

herds (Quebec), three herds (Trinidad) and aIl Government-kept

heifers were the only herds meeting energy requirements,

One herd (Quebec), and another (Trinidad) were deficient in

phosphorous, and one herd (Quebec) was also deficient in

protein intake.

In herds with high milk production significant

correla tions (P < O. Dl) were observed between services per

conception and milk production and between calving interval

and milk production. In the Trinidad herds services per

conception declined from 2.5 to 1.8 and calving interval from

443 to 407 days from first to third lactation respectively.

Heat detection was a problem in many herds due to

inadequate observation and failure to observe some heat

signs. More time spent observing cows for heat would greatly

reduce breeding problems.

NUTRITIONAL ASPECTS OF DAIRY CATTLE INFERTILITY IN QUEBEC AND TRINIDAD

by

Hezekiah Horatio Nelson

A thesis submitted to the Faculty o~ Graduate Studies and Research in partial ~ul~ilment o~ the requirements for the

degree o~ Master of Science

Department of Animal Science, Macdonald College of McGill

University, Montreal, Quebec

® Hezekiah Horatio Nelson

August 1972

1973

~t • r

RESUME

M. Sc. Hezekiah H. Nelson Animal Science Nutrition

Onze troupeaux laitiers du Québec, trente de Trinidad, plus les vache Holstein gardées sur les fermes du Gouverne­ment de Trinidad et un troupeau croisé du même Gouvernement ont été examinés afin de déterminer les facteurs (surtout nutritionels) affectant la fertilité. Le nombre des services par conception a été en moyenne de 2.1, 2.2, 3.0 et 2.7 et les intervalles entre chaque vêlage ont été de 399, 437, 488 et 435 jours respectivement. Seulement cinq troupeaux dont deux au Québec et trois à Trinidad, ainsi que toutes les génisses gardées par le Gouvernement de Trinidad rencontraient les exigences en energie. Un troupeau au Québec et un à Trinidad étaient déficient en phosphore et un troupeau au Québec était déficient pour l'ingestion de protéine.

Dans les troupeaux où la production laitiére était élevée, des liaisons simples significatives (P<:O.Ol) ont été observées entre le nombre de services par conception et la production de lait et entre l'intervalle entre chaque vêlage et la production du lait. Dans les troupeaux de Trinidad le nombre de services par conce~tion a passé de 2.5 à 1.8 et l'intervalle entre chaque velage de q.43 à 407 jours de la première à la troixième lactation.

La détection des chaleurs était un problème dans plusieurs troupeaux à cause d'une surveillance inadequate et de la difficulté à reconnaître certains signes de chaleur. Une augmentation de la période d'observation des vaches dans le but de détecter les chaleurs aurait grandement réduit les problèmes de fer~ilité •

. ;,

-'!' ....

ACKNOWLEDGElVIENTS

l wish to express my sincere appreciation and thanks

to Dr. E. Donefer, Animal Science Department, for his

guidance and advice in the research conducted, and in

preparing this thesis.

l should also like to express my thanks to Dr. J.

Moxley for assisting in the statistical analysis of the data.

l should also like to thank the followingl The Canadian

International Development Agency for the scholarship which

enabled me to undertake this study; the Trinidad and Tobago

Gov~rnment for the facilities and personnel placed at my

disposaI in carrying out the survey in Trinidad; Mr. E. Unsworth

for the use of the facilities at the University of. the West

Indies, Trinidad; the farmers,both in Quebec and Trinidad

for allowing their herds to be used in this study; my

fellow graduate students for the very valuable discussions

and help rendered at Macdonald College and aIl those who in

someway assisted me in this research. Finally l wish to

express thanks to my wife,Gwendolyn, for her patience and

encouragement.

TABLE OF CONTENIJ:S

1. INTRODUCTION ••••••••••••••••••••••••••••

II. REVIEW OF THE LITERATURE • • el. • • • • • • • • • •

A. Incidence of Nutritional Infertility

B. Specifie Supply of Nutrients ••••••••

1. Plane of Nutrition ••••••••••••••

2. Protein •••••••••••••••••••••••••

a. General •••••••••••••••••••••

b. Protein-effect on fertility •

3. MineraIs

a. General • • • • • • • • • • • • • • • • • • • • • b. Calcium • • • • • • • • • • • • • • • • • • • • • c. Phosphorous •••••••••••••••••

i. General • • • • • • • • • • • • • • • • • ii. Phosphorous effect on

fertility •••••••••••••••

d. Calcium to Phosphorous Ratio

i. General •••••••••••••••••

ii. The role of CaaP ratio ••

e. Manganese •••••••••••••••••••

f. Other MineraIs ••••••••••••••

4. Vitamins ••••••••••••••••••••••••

a. General • • • • • • • • • • • • • • • • • • • • •

b. Vitamin A • • • • • • • • • • • • • • • • • • •

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4

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13

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14

17

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18

21

21

22

28

28

28

34

39

41

41

42

C.

D.

Table of Contents (cont'd)

c. Vitamin D •••••••••••••••••••••

Effects of Feedstuffs • • • • • • • • • • • • • • • • • Causes of Nutritional Infertility •••••

Page

45

46

48

a. Lactational Stresses •••••••••• 48

b. Body Weight Change •••••••••••• 50

c. Blood Analysis Criteria ••••••• 52

III. OBJECT OF RESEARCH •••••••••••••••••••••••• 55

IV. DATA SOURCE AND METHODS ••••••••••••••••••• 56

A. Quebec Province ••••••••••••••••••••••• 56

1 • General. • • • • • • • • • • • • • • • • • • • • • • • • • • 56

2. Sampling Procedure •••••••••••••••• 56

a. Hay Samples ••••••••••••••••••• 56

b. Corn and Grass Silage ••••••••• 57

c. Grains or Concentrates......... 57

3. Blood Collection and Microhematocrit determination ••••••••••••••••••••• 57

B. Trinidad. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 58

1. Location and Climate •••••••••••••• 58

2. Sampling Procedure •••••••••••••••• 60

a. Pasture grasses ••••••••••••••• 60

b. Concentrates................... 61

3. Blood Collection and Microhematocrit determination ••••••••••••••••••••• 62

vi

l

Table of Contents (cont'd)

C. Feeding and Management •••••••••••••••

1. Quebec •••••••••••••••••••••••••••

2. Trinidad •••••••••••••••••••••••••

D. Ana1ytica1 Methods • • • • • • • • • • • • • • • • • • • 1. Preparation of Samp1es •••••••••••

2. Chemica1 Analyses ••••••••••••••••

a. Foragesand Concentrates •••••••

b. B100d Ana1ysis •••••••••••••••

3. Procedure to evaluate the energy content ofa •••••••••••••••••••••

a. Forages ••••••••••••••••••••••

b. Concentrates •••••••••••••••••

4. Other Data •••••••••••••••••••••••

E. Statistical Analysis of Data •••••••••

V. RESULTS AND DISCUSSION •••••••••••••••••••

1. Incidence of Infertility in Trinidad •••••••••••••••••••••••••

a. Services per Conception ••••••

.b. Ca1ving Interval •••••••••••••

c. Mi1k Production ••••••••••••••

2. Blood Components •••••••••••••••••

a. Serum Calcium ••••••••••••••••

b. Serum inorganic phosphorous ••

c. CaaP Ratio •••••••••••••••••••

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62

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70

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72

72

79

82

83

83

88

91

4.

5.

Table of Contents (cont'd)

d. Hematocrit (Packed Cell Volume)

Feed Intake •••••••••••••••••••••••••

a. Chemical Composition ••••••••••••

b. Energy ••••••••••••••••••••••••••

c.

d.

Protein

Calcium

• • • • • • • • • • • • • • • • • • • • • • • • •

• ••••••••••••••••••••••••

e. Phosphorous •••••••••••••••••••••

f. CalciumaPhosphorous Ratio •••• ~ ••

Simple Correlations between services per conception and calving intervals with various parameters ••••••••••••• a. Age ••••••••••••••••••••••••.••••

b. Body Weight •••••••••••••••••••••

c. Milk Production •••••••••••••••••

d. Lactation Sequence (Number) •••••

e. Blood Components ••••••••••••••••

i. Serum Calcium •••••••••••••••

ii. Phosphorous •••••••••••••••••

iii. Hematocrit ••••••••••••••••••

f. Feed Intake •••••••••••••••••••••

Summary of Simple Correlations between services per conception and calving intervals with other parameters •••••

a. Quebec Herds ••• ~ ••••••••••••••••

b. Trinidad Herds ••••••••••••••••••

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93

93

96

111

113

116

119

122

122

122

137

139

139

139

140

141

141

143

143

145

! .

Table of Contents (cont'd)

Page

c. Government Herd (Trinidad) ••• 146

i. Purebred Holstein •••••••• 146

ii. Crossbred Holstein/Zebu •• 146

6. A Comparison of Means of different Parameters between Quebec and AlI Trinidad Herds ••••••••••••••••••• 148

a. Body Weight •••••••••••••••••• 148

b. Mi1k Production •••••••••••••• 148

c. B100d Components ••••••••••••• ISO

d." Feed Intake •••••••••••••••••• 151

e. Lactation Sequence (Number) •• 151

f. Index of Ferti1ity • • • • • • • • • • • 15J

i. Services per Conception •• 15J

ii. Ca1ving Interva1 • •••••••• 7. Evaluation of effects of production

parameters on ferti1ity index.

154

Herd effects removed ••••••••••••• 156

8. Re1ationship between frequency of ca1vings and rainfa11, temperature and season of the year. (Trinidad) •••••••••••••••• 165

VI. SUMMARY AND CONCLUSIONS •••••••••••••••••• 169

LITERA TURE ClTED •••••••••••••••••••••••••••••• 175

APPENDIX TABLES ............ " ................. . 197

ix

LIS T OF TABLES

Table Page

1. Average Temperature in Trinidad • ••••••••••••• 59

2. Dairy Ration Composition ••••••••••••••••••••• 61

3. Estimated TDN and ENE content of Manufactured Dairy Feeds •••••••••••••••••••••••••••••••••• 68

4. The incidence of inferti1ity of catt1e in Trinidad ••••••••••••••••••••••••••••••••••••• 73

5. Mean Production and Reproduction Parameters for Cows (Quebec Herds) •••••••••••••••••••••• 75

6. Mean Production and Reproduction Parameters for Cows (Trinidad Herds) •••••••••••••••••••• 76

7. Mean Production and Reproduction Parameters for Cows (Government Herds Centeno, Trinidad) 78

8. Mean Concentration of B100d Components in Cows (Quebec Herds) •••••••••••••••••••••••••• 84

9. Mean Concentration of Blood Components in

10.

Il.

Cows (Trinidad Herds) •••••••••••••••••••••••• 85

Mean Concentration of B100d Components in Cows (Government Herds Centeno, Trinidad)

Mean Body Weight, Dai1y Production and Estimated Dai1y Feed Intake (Quebec Herds)

• • • •

• • •

87

97

12. Mean Body Weight, Dai1y Production and Estimated Dai1y Feed Intake (Trinidad Herds) 98

13. Mean Body Weight, Dai1y Production .and Estimated Dai1y Feed Intake (Government Herds Centeno, Trinidad) ••••••••••••••••••••••••••• 100

14. Summary of Requirements and Differences in Feed Intake (Quebec Herds) •••••••••••••••••••••••• 101

·x

List of Tables (Cont'd)

Table Page

15. Summary of Requirements and Differences in Feed Intake (Trinidad Herds) ••••••••••••• 102

16. Summary of Requirements and Differences in Feed Intake (Government Herds) Trinidad 104

17. Simple Correlations of Services per Conception and Calving Intervals with other Parameters (Quebec Herds) ••••••••••••••••••• 12;

18. Simple Correlations of Services per Conception and Calving Intervals with other Parameters (Trinidad Herds) ••••••••••••••••• 127

19. Summary of simple Correlations of Services per Conception and Calving Intervals with other Parameters (Quebec Herds merged, Trinidad Herds merged and the Government Herds, Centeno, Trinidad) ••••••••••••••••••• 144

20. A comparison of Means of different Parameters between Quebec and Trinidad Herds ••••••••••• 149

21. Means of Services per Conception and Calving Interval according to Lactation Sequence (Quebec Herds) •••••••••••••••••••••••••••••• 157

22. Means of Services per Conception and Calving Interval according to Lactation Sequence (Trinidad Herds) •••••••••••••••••••••••••••• 157

2;. Least Squares Estimates of the effects of lactation sequence on services per conception and calving interval (Quebec Herds) ••••••••• 159

xi

~ .... , List of Tables (Cont'd)

Table Page

24. Least Squares Estimates of the effects of lactation sequence on services per conception and calving interval (Trinidad Herds) ••••••••• 159

25. Least Squares Estimates of the affects of services per conception on various productive parameters (Quebec Herds) ••••••••••••••••••••• 162

26. Least Squares Estirnates of the effects of services per conception on various productive pararneters (Trinidad Herds) ••••••••••••••••••• 163

27. Least Squares Estirnates of the effects of services per conception on various productive parameters (Trinidad Government Herds) •••••••• 164

xii

j ... . r LIS T Olt~ FIGURES

Figure Page

1. Relationship between Cellulose Content (%) and TDN •••••••••••••••••••••••••••••••••• 69

2. Relationship between ENE (NVI) and age of pangola grass •••••••••••••••••••••••••••• 109

3. Relationship between ENE (NVI) and age of Napier grass •••••••••••••••••••••••••••• 110

4. Relationship between frequency of calvings and rainfall, temperature and season of the year ••••••••••••••••••••••••••••••••• 166

xiii

.INTRODUCTION

Whenever the world food problem is discussed

emphasis usually falls on theshortage of protein in those

countries referred to as developing. These countries lie

within the tropical and subtropical regions. Probably the

most difficult aspect of this food problem is to provide

supplies of protein adequate to assure good health.

Provision of adequate quantities of animal products is one

good way to help improve world protein nutrition.

Since we ourselves are animaIs, the proportions of

essential amino acids in the proteins of other animaIs come

much closer to meeting our needs than those in most plants.

Up to a few decades ago Animal Husbandmen had

accepted the dictum that development of organised dairying

under tropical and subtropical conditions was very nigh

impossible. However, with the possible exception of a few

limitations (particularly areas infested with the tse-tse

fly) such an undertaking is no longer considered to be

impossible or impractical.

During recent years many projects (for example in

India and Kenya) have been developed with United Nations

and bilateral aid,which have shown that production,

proçessing and handling of milk under unfavourable climatic

conditions are not only possible technically, but that such

developments have a considerable impact on the nutritional

_ .. f

2

and socio-economic conditions, and the general standard of

living of the population in the areas concerned.

In Trinidad the steady decline of the traditional

export crops such as sugar, cocoa, coffee, citrus and a

subsequent decline in the contribution of Agriculture to

the Gross Domestic Product (17% in 1953 to 10% in 1965)

caused a shift to a more diversified form of Agriculture.

The apparent success of tropical Puerto Rico in creating a

dairy industry with exotic cattle, gave an added impetus ,

for diversification along these lines so that Trinidad

embarked on importing Holstein cattle from various countries -

mainly Canada. The setting up of a dairy industry was

considered important since in 1964 Trinidad imported about

$30 million T.T. (about $15 million Canadian) worth of goods

comprising milk and milk products and Meat and Meat products.

Hence the development of a local dairy industry, and as a

consequence, the availability of Meat as a by-product

offerred one possible alternative to offset balance of pay-

ment problems.

Infertility is one of the largest economic losses

experienced in dairy herds. Losses are caused by retained

placenta, metritis, anestrus, silent estrus, cystic follicles,

repeat breeding and abortions. In Many instances, feeding

and other management practices, l such as inadequate observa­

tion of cattle, can predispose to, and accentuate infertility

problems.

J

Since the nutritional status of the individual animal

and of populations has a profound effect, both direct and

indirect, on their reproductive processes, studies on the

effects of nutrition on reproduction are of great importance.

Many of the cows in the world experience periods of under­

nutrition, especially before puberty and during lactation.

As animal husbandry practices improve, it would be expected

that problems associated with improper nutrition will decline.

However, it is quite clear that in both the advanced and

developing countries feeding and management practices give

rise to a situation where maximum reproductive performance

is essential, primarily from an economic point of view.

Inadequate nutrition can involve a shortage of food,

an excess intake of a balanced diet leading to obesity, or

alternatively, it can involve an excess or a lack of a

particular nutrient which might normally be required in

macro - or micro - quantities. AlI these situations can

leadto sUb-optimal reproductive performance.

As far as the main nutrients are concerned, it is

generally accepted that adequacy of these for health,

prOduction and growth in the young should provide sufficient

levels for fertility (Laing,1955).

The purpose of the study reported herein was to

relate, or identify if possible, the infertility of the dairy

cattle on the farms visited with their nutritional status,

and suggest possible areas of solution with specific emphasis

to the Trinidad situation.

ij ,

4

II. REVIEW OF THE LITERATURE

A. INCIDENCE OF NUTRITIONAL INFERTILITY

Few attempts to determine the occurrence and incidence

of nutritional infertility have been reported. Warnick

(1959) found that fertility rates were higher in non-1acta­

ting than in lactating cows, and that cows grazing pastures

of higher nutritive value (clover-grass) had higher ferti­

lit Y rates than those grazing grass pastures. The increase

in fertility as measured by calving percentage, was larger

in lactating (32%) than non-lactating (19%) cows on the

clover-grass pastures; and the interva1 from parturition

to first heat was reduced from 90 days to 72 days.

Donaldson g1 âl. (1967) found that, in six beef cattle

herds in Northern Queensland, Australia, the overall preg­

nancy rates ranged from 50% to 75%. The Mean pregnancy

rates were 36.4% in lactating and 77.5% in non-lactating

cows, and 79.8% in "fat", 65.9% in "forward store" and 39.9%

in "store" or poor body conditioned cows.

Donaldson (1968) also reported low productivity of

cows in a large herd and that only 57% of the cows calved in

two or more successive years, while 32% calved strictly in

alternate years. Cows calving tirst as two year-01ds

produced more calves than cows ca1ving tirst as three year­

olds or older, despite the severe nutritional and lacta-

5

tional strain placed on the cows calving at the younger age.

Lamond (1969a)reported that reproductive performance

in 13 herds of beef cattle in North-Eastern Australia,

showed that lactating heifers had lower pregnancy rates than

lactating cows, which in turn had lower rates than non­

lactating animaIs. He also observed that within classes,

cows in poor body condition had lower fertility than those

in "forward-store" or fat condition. His main conclusion

was that improved nutrition of lactating heifers and cows

would be expected to increase pregnancy rates substantially.

AlI these reports have been on beef herds and generally

refer to observations on selected herds.

However, in a disease wastage survey of dairy herds

in the Moss Vale district of New South Wales, Mc Clure and

Dowell (1968, 1969) reported evidence of reproductive

inefficiency not caused by infectious disease or male infer­

tility. This infertility was characterised by low first

service non return ("conception") rates, delay in, but

eventual establishment of pregnancy, and extended calving

intervals. The negative correlation between rainfall, and

the positive correlation between supplementary feeding and

high fertility suggested thatthere was sorne nutritional

component to this infertility and pasture-grazed cattle.

Reed (1961), quoted by Melrose and Brown (1962), in

a survey of one hundred national milk recorded herds, found

a close association between fertility and the acreage of

6

Kale (Brassica oleracea) grown. Winter fertility of cows was

lowered in herds where the percentage of Ka1e grown exceeded

9% of total farm acreage.

Thain (1967) in Tasmania, reported that a temporary

infertility was common despite the absence of vibriosis or

other recognizable infections. In a suryey . 29 of 49 dairy

herds (59%) grazed on subterranean and/or red clover-dominant

pastures had infertility problems compared with 10 of 62

herds (16%) fed pastures containing 1ittle or no clover.

B. SPECIFIC SUPPLY OF NUTRIENiS

1. Plane of Nutrition

Malnutrition, or an intake of an inadequate or faulty

diet, may cause reproductive failure. However, there is the

question whether the infertility May be due to specifie nutrient

deficiencies or whether it May be due to reduced calorie intake

which usually occurs in ma1nourished animaIs.

Many reports dealing with the influence of plane of

nutrition or intake of energy, both before and after partu­

rition, on reproductive performance indicate that feeding

from weaning on low levels delays or prevents the onset of

puberty, and that the subsequent addition of extra energy

rations causes heifers to come into estrus and conceive when

mated. Reid et al. (196~) found that feeding at the rate of

62% of Morrison's feeding standards, delayed the onset of

puberty to 88 weeks of age compared with 49 weekds for the

heifers fed at the 100% level. Similarly, Short and Be1lows

(1971) indicated that by increasing the winter feed level in

heifers, increased the weight at puberty with a corresponq-

j

î Or ° o~ -

7

ing decrease in age. Fewer animaIs on the low and medium

plane of nutrition came into estrus during the breeding

season, and the reproductive potential was lowest in heifers

on the low plane. These heifers tended to conceive 1ater

and also had a higher pregnancy loss.

Van Demark and Mauger (1964), Van Demark et ~.

(1964), and Mann et!!. (1967) showed that puberty in bulls

was similarly de1ayed by this treatment. Van Demark et al.

(1964) found that underfeeding of bulls for an extended

period during growth was detrimenta1 not only to growth and

development but also to sperm producing capacity. Further­

more increasing the plane of nutrition to 100% when the bull

was 46 months of age, appeared to have little effect on

fertility, as apparently the endocrine and reproductive

tract by that age, are re1atively unresponsive to increased

nutrient intake and therefore very little recovery from

underfeeding. At the same time reducing the energy intake

a t 46 months of age had li ttle effect in reducing the seme,n

producing potentials of a bull maintained at normal energy

recommendations up to 46 months.

A lowered plane of nutrition seemed to impair ovarian

function (Hart and Guilbert, 1928), However, Sorenson et al.

(1959) reported that on dairy females there was little

evidence that ovarian function was adversely affected by

either under or overnutrition once puberty was reached.

Joubert (1954) found that heifers on a low plane of nutrition

1

experienced an anestrous period during the winter lasting

up to 218 days and those heifers started recycling only

after adequate pasture became available and they recovered

their lost weight.

8

A low plane of nutrition during la te pregnancy seems

to delay the onset of the estrous cycles after parturition

and also depress first service pregnancy rates (Wiltbank

et al.,1962, 196~J Turman ~ al., 1964, Hight,1968).

Wiltbank et al. (1962) fed Hereford cows at two levels

of energy prior to calving and then after calving half the

cows on each level were switched tothe other level. The

amounts fed after calving contained an allowance for milk

production. The proportion of cows diagnosed pregnant was

95%, 77%, 95% and 20% for the cows fed the high-high, high­

low, low-high, low-low energy levels respectively. The

differences among these groups were due largely to a high

proportion of cows on the low energy level after calving

failing to show estrus.

Reynolds et ll- (1964) depressed fertili ty by fe"eding

Aberdeen Angus heifers on a 10w plane which limited their

weight gain to 60 pounds over a 12 month periode The work of

Turman et âl. (196~) suggested that the nutritive level of

he if ers during their first pregnancy has a carry-over effect

on reproductive performance at their second mating. This

could possibly account for the lower pregnancy rates in

first calf heifers observed by Young (1965).

9

High planes o~ nutrition after calving seem to over­

come the infertility effect caused by 10w planes in la te

pregnancy. Wiltbank ~ âl. (1964) observed that follicular

deve10pment was more obvious when the TDN intake was high

than when it was low; fertilization was more satisfactory

also. Cows which lost weight had the poorest results. There

was a relationship between the percentage of cows diagnosed

pregnant after the breeding period and the level o~ TDN fed

throughout the period after parturition.

Dunn et al. (1969) carried out detailed observations

on body weights and reproductive phenomena in hei~ers fed

known rations before and after parturition. Occurrence of

estrus during the first two months after calving was

greatest in the heifers fed a high-energy ration be~ore

calving. A low energy diet post-partum caused infertility

due to lengthening of the post-partum anestrus, and failure

to conceive even though the estrous cycles were of normal

length. Dunn et âl. also observed di~ferences in occurrence

of estrus between Aberdeen-Angus and Herefords fed low­

energy level diets after parturition. However, Gardner

(1969) found that in Holstein cows neither level of pro­

duction nor level of energy intake be~ore or after calving,

or both, had a significant effect on ~ertility.

Blakely (1965) quoted by Mc Clure (1970), wintered

three groups each of 16 Hereford heifers on three planes of

energy intake supplying 12.65 pounds, 9.66 pounds, and 4.24

l

10

pounds TDN respectively. The three diets contained "adequate

protein." AlI heifers were showing estrus before the trial

commenced but, after joining near the end of the trial, 15

of the 16 and 14 of the 15, respectively, of high and medium­

plane heifers mated were pregnant, and only one of the two

that were mated in the group receiving 4.24 pounds TDN was

pregnant. One of the 16, and 14 of the 16 heifers,

respectively, in the medium and low-plane groups failed to

show signs of estrus at the time of breeding.

Rakha and Igboeli (1971) maintained 40 ranch cows of

Central African origin under two planes of nutrition for a

full calendar year. By the end of the experimental period

55% of the animaIs on the low plane had stopped cycling.

The incidence of silent ovulation in the low plane group

was significantly higher than in the group on the normal

plane of nutrition and there appeared no seasonal effects on

either length of the estrous cycle or estrous period of the

latter group.

Mc Taggart (1961) reported the effect on fertility

of over-estimating the carbohydrate available to milking

cows at pastùre. In a problem herd of 35 cows, Il were

infertile and most of these were giving 4 gallons per day

although it was shown that the pasture, not suppl emented,

contained starch equivalent for only 2 gallons. Abortions,

returns to service and prolonged heat intervals were

characteristic; though lower yielders merely tended not to

i ~-

11

exhibit heat. Similarly, Mc Clure (1961, 1965) and Mc Clure

and Dowell (1969) observed infertility syndromes in pasture­

fed dairy cows characterized by first-service pregnancy

rates of about 30%; and an improvement in fertility when

the pastures were supplemented with concentrates and hay.

Prior to these results, Le Roux (1960) in Natal, observed

the same phenomena, directly linked with depressed fertility,

which resolved when either a maize Meal or coarse hay

supplement was fed.

The co-occurrence of low solids-not-fat in milk with

infertility has been noted, and attributed to insufficient

carbohydrate intake. Gould (1966) quoted by Dawson (1967),

has encountered one such case showing low solids-not-fat

with infertility in late winter; these are corrected on

turning out to grass, yields increase, indicating that the

pasture provided a more adequate concentration of nutrients

than what was previously fed.

Po or quality of forage and reduced intake of nutrients

due to the climate lead to infertility in tropical and sub­

tropical areas (Mahadevan, 1966). Anestrus is the MOSt

common symptom, but too Many cows require more than one

service for pregnancy. Late maturity (cows often not calving

for the first time until they are 4 years old), and prolonged

calving intervals are quite common in tropical (Bos indicus)

breeds of cattle. However, there is no clear indication

whether infertility in tropical breeds is due entirely to

- .. '

t. poor nutrition or is associated with selection for such

characteristics as dual-purpose Meat and milk, draft or

survival.

12

According to Swanson (1967) there is a rate of

growth for each breed of dairy heifer, which is optimal for

conception at about 15 months of age. If dairy heifers are

grown faster than the optimum the maintenance requirement

becomes too costly when the animal is young. Also rapidly

grown heifers tend to have inferior productive performance

compared with heifers grown at a moderate or slow rate

(Reid et al. 196~).

Similarly Hentges ~ al. (1964) fad bulls concentrates

ad libitum for Il months from Il months of age and caused

obesity and loss of libido, particularly during hot weather,

but ch~nges in semen quality were negligible.

Morrow et al. (1969) reported that feeding high

producing dairy cows a liberal ration of concentra tes

resulted in development of a high incidence of cystic folli­

cles, pro1onged calving intervals and more services per

conception than the controls. However, results from work

by Armstrong et~. (1966) and Gardner (1969) indicated

that neither level of production nor level of- energy intake

before or after calving, or both, had a significant effect

on ferti1ity.

On a physio1ogical basis Leathem (1966) pointed out

that undernutrition reduces secretion of gonadotrophin from

1)

the pituitary gland in Most species. Subsequently, Lamond

(1968, 1970a) showed that the plane of nutrition influenced

the ovarian response to gonadotrophine Also he observed

that fasts for 72 hours during the period after injection

of pregnant mare serum gonadotrophin (PMS) reduced folli­

cular development.

Short-term effects of a sub-maintenance ration

studied by Hill et al. (1970) showed changes in ovarian

morphology, length of the estrous cycle and plasma progeste­

rone level, and poor fertilization of ova. Later studies

suggested that considerable variability in the short-term

effects of undernutrition on reproductive phenomena was

associated with the variation in nutritional status of the

animaIs at the beginning of the experiment (Lamond,1970b).

2. Proteins

a. General

Proteins are fundamental to life for they govern and

take part in aIl phases of the activities of the living

cell; they serve as structural elements in soft tissues and

play a part in the metabolism of skeletal tissues.

Proteins are made up of some twenty different amino

acids and those which cannot be synthesized in the non­

ruminant or calf in its pre-ruminant stage, or at a rate

adequate to meet the needs for growth and reproduction are

termed essential and must be supplied in the diet.

In the case of the ruminant, microbial synthesis can

\ ..

r .-

f

14

partially overcome the need for preformed protein or

essential amino acids to be supplied in the ration, for

the bacteria and protozoa can synthesize protein from non­

protein non-amino acid sources such as urea and ammonium

salts and in amounts sufficient to sustain milk production.

Jakobson (1957) as reported by Dawson (1967), calcu­

lated the protein requirement of the developing fetus as

rising from 38 to 225 gm daily (expressed as digestible

pure protein) between the sixth and ninth month. In

contrasting the amino acid content in maternaI blood, and

in deposited fetal protein, with that in the usual protein

concentrates fed to cattle, he concluded that the lysine

and methionine requirements tended not to be met from the

forage unless the quality synthesized in the rumèn should

prove adequate.

b. Protein effect on fertility

It does seem as though sorne infertility encountered

is due to insufficient protein or to the po or biological

value of that supplied. Janzen (1957) found a casein

preparation to be far more effective than either cod liver

oil or a mineraI salt supplement in curing infertility

problems of nutritional origin in the Hanover neighbour­

hood.

DawsBn (1967) stated that reports by Richter (1957-

58) indicated that an addition of methionine to the ration

would cure obstinate cases of the liver dysfunction which

.... -"'

lS

has been associated by several workers,with cystic ovarian

disease, and hence the infertility observed in these animaIs

had also been resolved.

In a comparison of Brahman cattle and Herefords in

the Florida environment Howes ~ al. (196) showed that diets

in which crude protein was SO% below normal (total intake of

TDN also sUb-optimum), delayed puberty and jeopardised sub­

sequent reproductive performance. It was considered that

the higher milk production of lactating Brahman cows necessi­

tated a higher level of food intake to maintain adequate

reproductive function, and when the food was not readily

available the Brahman cows had longer periods from partu­

rition to conception than the British cattle.

Bedrak ~~. (1964) also found that low intakes of

0.28 and 0.08 pound crude protein per day for 6i months

delayed or inhibited puberty in heifers initially weighing

SOO pounds.

Similarly Wiltbank et/al. (196S) fed heifers from

400 pounds body weight, until 180 days after first calving

or until 90 da ys pregnant with their second calves, on

three levels of energy, ad libitum, 66% ~ libitum, and

sufficient to maintain body weight, and on three levels of

protein 0.2), O.lS, 0.06 pound per 100 pound body weight

per day respectively. Most heifers on low energy and Many

on low protein intakes did not reach puberty. Those on high

and low protein diets were able to maintain only low intakes

16

and therefore it was not clear as to whether the effect was

due to low protein or low energy intakes.

Warnick et ~. (1965) raised heifers of various

breed types on two different.types of pasture and with two

levels of protein supplementation in the winter. At two

years old the heifers were aIl put on good quality pasture.

It was found that levels of protein supplementation did

not influence reproduction la ter on, (calving rate of 89%

vs 88% with low protein) but those on clover-grass had 96%

calving rate vs grass pasture of 81%. Also heifers on the

clover-grass pasture grew better and continued to produce

better throughout the next few seasons than did those on

grass alone. Of interest is the fact that grass plus

protein supplementation did not give as good results as

grass-clover, and raises the question of the importance of

legume-grass swards for cattle production.

Similar work by Cunha et al. (1966) indicated that

a deficiency of protein in the ration of beef cattle retarded

growth and development of young animaIs, reduced fertility

of the breeding herd and reduced the appetite and gains of

fattening cattle.

Experimental evidence such as those mentioned above,

are not so common with dairy cattle. Perhaps this is due

to the fact that dairy heifers, and most particularly

dairy cows, are seldom required to obtain their sole sourcè

of dietary protein from grazing, whereas many beef cattle

17

are range managed. Another point is that in Many instances

the direct effects ·of protein deficiency on reproduction in

cattle have been difficult to de termine because of other

dietary deficiencies.

However, Girou and Brochart (1970), in a population

of 1300 cows, observed a trend of decreasing fertility when

the protein supply was excessive, and the phenomena being

confirmed when analyzing the observations made in an experi­

mental herd of 49 cows during three consecutive years. In

this he rd the energy supply was adapted to the requirements

each week, and the protein supply being qualitativèly and

quantitatively variable. They found that the threshold of

excess of digestible nitrogenous matters compatible with

normal fertility, to be between 200 and 300 gm per day

(p (,..01) .

3. MineraIs

a. General

The study of animal mineraI nutrition is very complex,

and although it is convenient to discuss each element

individually, many function in the body in pairs or groups.

Some mineraIs occur as structural components, and a number

act as enzyme activators. In some instances sorne elements,

example,calcium and molybdenum, may interfere with the

absorption and activity of other elements. This inter­

action of mineraIs with each other is an important factor

:-::1--

in animal nutrition, and an imbalance of mineraI elements

as distinct from a simple deficiency, is important in the

determination of certain nutritional disorders of farm

18

animaIs. Supplementation of any diet with mineraIs should

always be carried out with care.

b. Calcium

Calcium is the most abundant mineraI element in the

animal body and is in the greatest demand during the growth

periode For Many years calcium has been recognised as a

critical nutrient in the ration of dairy cattle, but adequate

data on requirements have not been available for aIl phases

of growth and reprOduction. Moreover calcium and phosphorous

have a chemical affinity for each other, and therefore

suitable calcium to phosphorous ratios in the ration as a

whole have been found to be of importance.

Asdell (1955) reported that there was no evidence

that a deficiency of calcium in the feed caused reprOductive

troubles, but there was a good deal of circumstantial

evidence linking the importance of calcium-phosphorous with

reproduction. Generally it has been assumed that many cows

consume enough calcium from forage crops, particularly

those fed on legumes, since forages are comparatively high

in calcium.

Fitch et al. (1932) reported that both milk production

and reproduction were essentially the same on three rations

that contained 0.64, 0.32 and 0.18 per cent of calcium

19

respectively, on a dry matter basis. They la ter reported

(1935) that when the cows that had received calcium at the

0.18 per cent level for several years were fed a 0.12 per

cent calcium level, there was no adverse effect on repro­

duction or on the production: of milk and fat.

Since it has been regarded that cows consume enough

calcium from forages most research work has been confined

rather to calcium to phosphorous ratios and effects of

phosphorous intake upon reproduction.

Ward et al. (1971) compared the effects of two

calcium intakes, averaging 100 and 200 gm, fed in rations

contributing 80 to 100 gm of phosphorous daily, on repro­

ductive performance of 37 two to six year old Holstein cows

through 58 reproductive cycles. The experimental group of

animaIs received 300,000 l.U. of vitamin D3 weekly whereas

the controls did note They found that uterine involution

was completed eight days sooner (P<.05) in both rations

fortified with vitamin D3 but that first ovulation occurred

six days earlier (P~.05) in cows fed 200 gm calcium than

those fed 100 gm and this influence was not due to supple­

mental vitamin D. The first recognizable post partum estrus

occurred 16 days earlier (p (.06) and conception occurred 37

days earlier (P < .025) in the vi tamin D supplemented than in

the unsupplemented cows. However there was no significant

differences in services per conception among the treatments.

lt would appear that apart from lowered bull

j

20

fertility which can result from ove rwork, mineral intakes

which can lead to impaired breeding performance in females

can also have an adverse effect on the fertilizing capacity

of bull semene

Hignett (1959) reported that at a cattle breeding

centre two 'bulls, which during the previous 12 months had

conception rates of 59 per cent (based on 1,267 artificial

inseminations) and 65 per cent (based on 693 artificial

inseminations) respectively, were given large calcium supple­

ments (1.3 lb chalk per day), Within 3 to 6 months, the

conception rates had fallen to 33 per cent (based on 624 and

274 artificial inseminations respectively). Six to ten weeks

after withdrawa1 of the calcium supplement, the conception

rates had again risen to 53 and 46 per cent (based on'"118

and 112 artificial inseminations) respectively. Only the two

bulls receiving the chalk at the centre had this low level

of fertility.

It was pointed out that, possibly one of the most

interesting features of the observation, was that at no

time could any deterioration in semen quality be detected

in the laboratory. Thus it would appear that faulty feeding

can influence adversely the fertiliz:ing capacity of semen

before gross changes in the seminal picture become evident.

It is easy to realiz.e that, when the rations fed to

bulls, cows and heifers on a particular farm have mineral

levels likely to lead to impaired fertility, a serious

, j

21

breeding problem can result (Rignett, 1959).

In young calves a calcium deficient diet prevents

normal bone growth and retards general growth and develop­

ment. Their bones are low in calcium and fracture sponta­

neously. In mature cows, the feeding of rations low in

calcium over a long period of time may cause a depletion of

calcium and phosphorous in the bone$ resulting in fragile,

easily fractured bones and in reduced milk yields, but there

is no reduction in the calcium concentration in the milk

(Converse, 1954).

c. Phosphorous

i. General

By virtue of its role in the processes of energy

exchange, phosphorous is very closely associated with the

normal function of aIl animal tissues. Thus it is con­

ceivable that any limitation to the phosphorous supply may

be reflected in a general impairment of the animal's body.

function.

TOday, it is a known fact that the successful

completion of many important metabolic reactions depends on

phosphorylation. Renee, it is not surprising therefore,

that early effects of phosphorous deficiency are those of

retardation of growth due to reduced appetite, lowered

reproduction and lactation.

During the early stages of phosphorous deficiency the

22

supply necessary for body function is obtained from skeletal

reserves. Continued depletion results in skeletal disorders

shown clinically by bone fragility.

T~e first evidence of deficiency is that blood plasma

inorganic phosphorous declines to subnormal levels. Normal

values are 4 to 6 mg per 100 ml for cows and 6 to 8 mg per

100 ml for calves under one year of age (Anon., 1971). The

first clinical symptom of deficiency is anorexial • Depraved

appetite - chewing of substances not ordinarily classified

as feed, such as wood, bones and hair - is often observed.

Cows, however,may suffer from phosphorous deficiency with­

out manifesting depraved appetite.

ii. Phosphorous effect on fertility

The exact relationship between phosphorous and

fertility is not clear. In fact, reports in the literature

have been quite contradictory. Phosphorous deficiency has

been linked with reduced efficiency of feed utilization

(Theiler ~ ~.,1924). Riddell et al. (1934) showed that

the digestibility of feed was not impaired by phosphorous

deficiency, and this was confirmed by Kleiber ~ al (1936).

It has been demonstrated that phosphorous deficiency has an

adverse effect in the utilization of both energy (Kleiber

et al.,1936) and nitrogen (Stewart 1934 - 1935, quoted by

Little, 1970; and Morris and Ray, 1939). According to

lLack or loss of appetite

23

Morrow (1969), since the primary effeet of malnutrition on

fertility is anestrus, the infertility May be due to both

a low energy intake and a specifie deficiency.

Eckles ét al. (1935) in Minnesota reported that on

Many dairy farms on which there was a phosphorous deficiency,

not more than one calf was obtained from a cow every two

years, but there were not more than the usual number of

abortions. Many heifers often failed to come into heat

until they were past two years old. Cows tended to have

sub-normal ovaries and those that were affected tended to

have one or two heat periods after they had given birth to

a calf. If they became pregnant ai this time the calves

were carried to term; but if not, they tended to become

anestrus for the remainder of their lactation. Eckles at

~. concluded that the disturbances in estrus and the low

calf crops reported under natural conditions in phosphorous

deficient areas are probably due to the nutritive deficien­

cies which accompany the lack of phosphorous or to the

combination of deficiencies that prevail and not exclusive­

ly to phosphorous deficiency.

Similarly Theiler ~~ ~l. (1937) as reported by Little

(1970), observed estrus and normal ovulations in grossly

phosphorous deficient heifers during an experiment in which

approximately 3 gm of phosphorous per day was fed over an

extended periode

Subsequently, Palmer ~ al. (1941) studied combined

24

phosphorous and protein deficiency and found that sexual

maturity in heifers was delayed, there was repression of

normal evidences of estrus so that periods of estrus

appeared to be missed, but there was no interference with

normal regularity of ovulation or the ease of conception.

The reduction in breeding efficiency observed by these

workers in their previous experiment (Eckles ~ gl., 1935)

when phosphorous alone was deficient, was not observed in

this study, however, there was marked dystocia (mainly

maternaI) in four of the eight animaIs employed for the

breeding study and they considered this could be attributed

in a large measure to the dietary deficiencies imposed.

Aphosphorosis has been linked with infertility by

Sheehy (1946), O'Moore (1950), and with infertility without

clinical symptoms by Hignett and Hignett (1951). In the

subclinical cases aphosphorosis was associated with unthrifti­

ness, low milk yield in dairy cows and anestrus or estrus

with repeated failures to conceive after service. Of the

clinical cases, first-calf heifers usually exhibit the

severest symptoms, while mature calves and cows were not so

seriously affected.

Sheehy (1946) found that feeding à supplementary

mineraI of sterilized bone flour at the rate of 2 oz. per day

or Meat and bone Meal (containing 34 per cent of calcium

phosphate) at the rate of t lb per day caused alleviation

of the disordered condition within a few weeks~ and

1

\

25

completely restored the affected animaIs to normal appearance

and health and reproductive activity in six to twelve weeks.

It appears that various types of ovarian dysfunction

have occurred at different phosphorous levels (Hignett,

1950). Anestrus was observed with low phosphorous levels,

whereas silent and irregular estrous periods were associated

with moderate deficiencies and infertility with marginal

levels.

Hignett and Hignett (1952) claimed that an intake of

about 50 gm of P205 daily was compatible with satisfactory

fertility in dairy heifers. This and other evidence, however,

was criticised by Abrams (1952b), who felt that the doubtful

vitamin D status of British cattle cast doubt upon conclu­

sions about the effect of phosphorous deficiency as such on

bovine fertility. Subsequently, Littlejohn and Lewis (1960)

obtained no difference in fertility between animaIs given

2.0 and Il.4 gm of phosphorous per 100 kg, in contrast to

the findings of Hignett and Hignett (1952).

It has been inferred, for example, by Underwood

(1966), that adverse effects on estrus and conception are

those of a specifie phosphorous deficiency.

O'Moore (1952) cited a controlled experiment in

Ireland where extra protein when fed over a period in the

form of a high protei~low phosphorous supplement to anestrus,

hypophosphataemic cows on phosphate-low grazing pastures,

failed to bring about a recurrence of estrus. On the other

26

hand, cows which were pastured on the same grazings and

which had been anestrus from 3 to 5 months, came in estrus

when fed disodium phosphate daily over periods ranging from

10 to 3.5 days.,

O'Moore (1960) stated that a lactating cow grazing

on pasture containing 0.15% phosphorous will rapidly develop

unthriftiness, anestrus, low milk yields and retarded growth.

By way of contrast, however, the highest level of phospho­

rous in South African pasture recorded by Bisschop (1964)

in 23 years of monthly sampling was 0.13%; the mean level

in the diet of animaIs grazing these pastures was less than

0.1%. Bisschop (1964) concluded that at no time did the

natural pasture provide sufficient phosphorous or crude

protein for optimum production. However, both dairy and

beef type cows were shown to have grown and reproduced

under these conditions, although rather inefficiently. Per­

haps, it is probable that the specialized functions and

nutritional demands of high producing dairy cows are such

that extrapolation to the beef situation may not be justi­

fied.

In a report by Snook (1964) it was observed that low

conception rates in high producing dairy cows were associated

with low blood phosphorous concentrations, which was unex­

pected because of normal (but unstated) levels of phospho­

rous in the pastures. A daily supplement of 20 gm of

phosphorous produced a graduaI response in terms of increased

,.. ," -'.,

butterfat production and reduced calving interval over a

number of lactations.

The close relationship between phosphorous and

prote in deficiencies was again emphasized by the results

27

of feeding trials in the Northern Territory of Australia

by Hart and Mitchell (1965). Supplementation of open range

beef cows in areas deficient in phosphorous, with 8 gm

phosphorous as monosodium orthophosphate per head per day

improved body weight and fertility, but fertility was

increased only in the lactating cows and not in the dry

cows (a pregnancy rate of 60% in the treated group as

compared with 41% in the controls). The authors considered

that the provision of protein is of equal if not of greater

importance than phosphorous for efficient animal production

in that area.

Recently, Morrow (1969) reported a response to

phosphorous supplementation by heifers, in terms of a

reduced number of servic~s per.conception. The phosphorous

deficiency resulted from intensified husbandry and cropping

practices which depleted the level of phosphorous in the

soil and consequently in the crops. Calculations of intake

and requirements for protein, energy, calcium and phospho­

rous showed that the phosphorous intake was deficient. The

clinical signs observed were rough coat, depraved appetite

and infertility. The number of services per conception

ranged from 3.7 before phosphorous supplementation to 1.3

28

after phosphorous supplementation. Blood analysis

indicated that the levels of blood calcium, carotene,

vitamin A, hemoglobin and protein were normal whereas low

blood phosphorous levels of 3.9 mg/lOO ml verified the

deficiency. The feeding of dicalcium phosphate free choice,

to these heifers restored blood phosphorous levels to a

normal range (6.6 mg/lOO ml) and fertility was restored.

d. Calcium to Fhosphorous Ratio

i. General

There is a wide variation in the calcium and phospho­

rous content of feed ingredients. Legumes are usually high

in calcium and low in phosphorous. The ratio is frequently

6.1 or higher. Grasses are relatively lower in calcium

with an approximate 211 ratio (Morrow,1969).

The level of calcium in the soil has little direct

effect on the calcium content of the plant. If the pH of

the soil drops too low, plants high in calcium, such as

legumes, do not grow; however, the phosphorous content of

the plant varies directly with the level in the soil(Anon.

1965). Generally, due to intensified husbandry and cropping

practices, the phosphorous content of many soils have become

depleted, so that it is important to analyse the forages,

especially for phosphorous content.

ii. The role of CalF ratio

The U.S. National Academy of Sciences (1971) recommends

., \

29

that the diet of a growing heifer and a dry cow should

contain 3.4 gm of calcium and 2.6 gm of phosphorous per Kg

of dry matter daily,(1.3Il ratio) and for a lactating cow

producing 20 - 30 Kg of milk daily the diet should contain

4.7 gm calcium and 3.5 gm of phosphorous per Kg of dry

matter daily (l.3al ratio).

Much interest in the relationship between the calcium.1

phosphorous ratio in the food and fertility levels of cattle

has been generated throughout the world. It is believed

that the utilization of phosphorous is impaired when the

ratio of calcium to phosphorous in the diet varies appre­

ciably from the commonly accepted optimum of 1-2.1, parti­

cularly when the level of phosphorous is marginalo

Webster (1932) suggested that New Zealand herds

grazing pasture with an adverse calciumlphosphorous ratio

had lower fertility than others on a more suitable ratio.

Hignett and Hignett (1951) from an analysis of the

relationship between intakes of phosphorous and calcium

and the fertility of cows and heifers, concluded that when

phosphorous intake was low a rise in the calcium intake

impaired fertility, but when phosphorous intake was high a

low calcium intake was often associated with low fertility,

with an increase in calcium intake improving breeding

efficiency. However, Hignett and Hignett (1953) found

that the vitamin D status of the animal might influence

fertility. With a high vitamin D status, fertility was not

i ~

\

JO

related to phosphorous intake but with a low vitamin D

status ferti1ity was improved on1y with a rise in phospho­

rous intake. In animaIs having a low phosphorous intake,

the effect of the calciumlphosphorous ratio on ferti1ity

was apparently influenced by the vitamin D status, and

conception rate decreased more markedly with widening ratio

as the vitamin became depleted.

O'Moore (1952) observed more severe signs of aphos­

phorosis on farms where the pasture exhibited a high

calciumlphosphorous ratio and on one farm there was evidence

for suspecting that a heavy application of ground limestone

to alkaline soi1 may have been a factor in the subsequent

occurrence of "bog lame" and low ferti1ity in the grazing

stock.

A critical experiment on the ro1e of the calcium.

phosphorous ratio on reproduction was reported by Litt1ejohn

and Lewis (1960), where ratios between 0.8 and 12.1 had no

effect whatever on ferti1ity. However, growth rate was

slightly depressed at the high ratio when the phosphorous

intake was approximate1y 2.0 gm per 100 Kg body weight.

With an adequate phosphorous intake of approximate1y

12 gm per day, Dowe et al. (1957) reported that the growth

rate of steers was significant1y depressed by ratios of 9

and 1)11. They conc1uded that if gains are used as a

criterion, then a critica1 ca1ciumsphosphorous ratio may

exist between 4.J11 and 9.1.1.

J .

]1

In a similar experiment in determining the optimal

calcium:phosphorous ratio or the range over which the ratio

may vary without harmful effects on growing cattle, Wise

et al. (196]) found that performance and nutrient conversion

were markedly decreased with calciumlphosphorous ratios

lower than laI. Ratios between 1.1 and 7:1 gave similar

and satisfactory results, but ratios above 7:1 resulted in

decrease performance and nutrient conversion values, but

adverse effects were not as marked as with ratios below 1.1.

Work by Ricketts and Campbell (1971) also established

that there was very little difference in growth rate of

Holstein steers fed a calciumlphosphorous ratio of 411 and

1:1 but steers fed 811 ratio gained much less. Also steers

on the 811 ratio had the lowest feed efficiency, converting

18.4 per cent of feed consumed to body weight, but not

significantly different from 19.6 per cent conversion with

a 1:1 ratio and 18.8 per cent conversion with the 411

calcium:phosphorous ratio fed.

Dawson (1967) reported that in a carefully p1anned

breeding experiment by Koefoed-Johnson (196], 1964)

intended to investigate the effects of varying calcium.

phosphorous ratios and vitamin A and D intakes on ascending

levels of phosphorous content in the ration; the main

result achieved was to show that the group of heifers on

the lowest phosphorous intake had more prolonged interva1s

between heats (mean 1ength 76 days) than in aIl the other

groups put together, although the former group was fully

fertile when served. After calving, however, 5 out of 8

of these heifers developed serious disease states,

32

including endometritis and 3 of the 8 calves were subviable,

while nothing comparable was shown among the other groups.

Further work in Spain by Sanchez-Garnica Montes and

Brenes Paya (1963) indicated various types of infertility,

and also osteomalacia in dairy cows housed aIl the year

round and never exposed to direct sunlight. In every

he rd phosphorous intake was similar - borderline - and it

was the widely varying calcium intake, level which de ter­

mined, with the universal vitamin D deficiency (which was

only presumed to exist) the extent of infertility and bone

disease in any given herd.

Ward ~ al (1971) studied the reprOductive performance

of 2 to 6 year old Holstein cows fed calciumaphosphorous

ratios of 0.9al, 1.311, 2.1.1 and 2.511. The phosphorous

intakes averaged about 80 to 100 gm per cow daily wi th sorne

groups receiving 300,000 I.U. of vitamin D3 weekly. AlI

groups had essentially the same reproductive performance and

there was no difference in services per conception.

Steevens et al. (1971) investigated the effects of

different ratios and percentages of calcium and phosphorous

on milk production, reproduction, blood mineraI values and

occurrence of disease conditions in 48 dairy cows over an

extended period of time. One group of cows received a

33

calciumlphosphorous ratio of 311 with 0.4 per cent

phosphorous in the ration. The second group had a ration

with the calciumlphosphorous ratio of 311 but with 0.6 per

cent phosphorous and the third group was provided with 0.6

per cent phosphorous and a ratio of 1.511. They reported

very little difference in breeding performance of cows in

the different groups in the first year in days from calving

to first estrus and number of services per conception.

Four animaIs in the first group fed 0.4 per cent phosphorous

develpped ovarian dysfunctions of follicular cysts, delayed

ovulation and persistent corpus luteum. During the next

breeding season the results were basically the same, however,

a great number of services per conception was required in the

lower phosphorous group.

The findings of Steevens et al. (1971) seem to agree

very closely with results reported by Littlejohn and Lewis

(1960), in that there was no significant difference in

reproductive performance between groups fed rations with

varying calciumlphosphorous ratios.

The available evidence reviewed suggests that the ratio

and percentages of calcium and phosphorous are important con­

siderations in formulating rations for dairy animaIs. The ratio

of calcimn to phosphorous in bone is about 211 in older animaIs

and feeding of diets with wide variations in calcium to phos­

phorous ratio may lead to other disturbances. For example an

increased incidence of parturient paresis in cows fed an

34

excess of calcium in relation to phosphorous during the dry

period was noted by Boda and Cole (1954). Stott (1965)

reported a field study in which the incidence of parturient

paresis was markedly reduced following alternation of the

dietary calciumlphosphorous ratio by decreased calcium and

simultaneously increased phosphorous intake. More recently

Kendall ~ gl. (1968) found an unusually low ratio of calcium.

phosphorous during the dry period equally as detrimental as

an extremely high ratio in terms of the occurrence of

parturient paresis. A dietary calcium to phosphorous ratio

of approximately 2.211 is adequate for reducing the incidence

of parturient paresis (Kendall et al., 1970).

e. lVIanganese

AlI animal tissues contain manganese in low

concentrations, and the variability of concentrations within

tissues and species is very small. The highest concentration

normally occurs in bones, liver, kidney, pancreas and the

pituitary gland (Underwood, 1956), the concentration in

these tissues in most species being between 2 to 4 p.p.m.

on a fresh tissue basis.

Deficiency of manganese in the diet of rats, mice

and rabbits is associated with impaired growth, defective

mineralisation and structure of the bones and depressed

reproductive function in the female. Histological

examination of the ovaries of rats and rabbits showed no

r

(

35

significant defects, but in the male rat and rabbit

sterility and loss of libido were associated with extensive

tubular degeneration and lack of spermatozoa, (Underwood,

1956).

Hignett (1941) suggested that the heavy liming of

pastures was associated with delayed ovulation in cattle

and this he attributed to a manganese deficiency.

Bentley and Phillips (1951) reported that dairy cows

on a diet marginal in manganese content showed delayed

estrus, a slightly reduced conception rate and a greater

number of calves were born with weak legs and pasterns at

the first calving. There also existed, at that time, in

Wisconsin a nuisance sterility of about 10 per cent of

certain dairy herds where low manganese rations were fed

and this was persistent on farms where the forage manganese

content fell below 20 p.p.m.

Wilson (1952) found that in herds which exhibited a

high incidence of anestrus, especially in heifers a

supplement of 15 gm manganese sulphate, 1 of copper sulphate

and 240 mg of potassium iodide daily increased conception

rate from 37.2 par cent in controls to 61.9 per cent in

treated animaIs. From then on the severe infertility

problem from one of these herds was controlled by manganese

sulphate therapy, and in subsequent cases of functional

infertility in other herds, acid sodium phosphate or

manganese sulphate, either with or without copper sulphate

and potassium iodide, was recommended, usually with

apparently successful results.

Another report by Munro (1957) indicated that out­

breaks of apparently functional herd fertility (associated

wi th herbage manganese_ levels ranging from Il to 26 p.p.m.)

decreased and conception rates improved immediately after

manganese was added to the diet. Conception rates to

either the first or second inseminations rose from 48 per

c:ent with 75 cows to 72 per cent wi th 74 cows for the year

prior to supplementation, and the year following, respective­

ly.

A report from Rolland (Grashins et al. 1953, quoted

by Underwood, 1956) indicated that a manganese dèficiency

occurred in young cattle on certain sand and peat soils.

These showed symptoms of poor growth and body development,

leg deformities and "over-buckling" of the pastern, po or

fertility, frequent abortion, and the cattle had poor coats

with loss of hair pigment. These symptoms responded to

2 gm of manganese sulphate daily. The ovaries contained

only 0.6 p.p.m. of manganese in the dry tissue.

The Dutch worker, Tesink (1962), was able to raise

conception rate at first service from an average of 51 to

69 per cent in a large group of problem herds by feeding

720 mg manganese per head per day. In a small scale trial

(1963) he fed this level at calciumlphosphorous ratios of

1.6 and 3.0 to normal animaIs and found at the ratio of 3.1

37

there was no significant rise in manganese content of hair,

whereas at the 1.6.1 ratio there was a significant rise.

Additional evidence of the part manganese deficiency

can play in causing bovine infertility has been provided by

an extensive field study conducted in south-western England

by Wilson (1966). Half of the cows in 12 irSertile herds

pastured on low to medium manganese content soils were

given 4 gm of manganese sulphate daily with a resulting

first service pregnancy rate of 63% compared with 51% for the

control cows (P~0.05). The clinical signs shown included,

anestrus, infertility, and in some herds po or growth rates

and knuckling over of fetlocks in calves. Wilson found that

available soil manganese was often low in south-western

England, due sometimes to the effect of heavy liming, and

recommended for optimal fertility the available soil

manganese content should not be lower th an 3 p.p.m. and the

content of roughage 80 p.p.m.; 50 p.p.m. appeared to be

the critical level especially when calcium intake was high.

Wilson further observed that the incidence of abortion

due to Brucellosis in cows vaccinated against this disease

was raised when manganese appeared deficient and in such

cases could be reduced by feeding a manganese supplement.

This finding was subsequently confirmed by observations

from practice by Bourne (1966), who also found it necessary

to feed 100 mg manganese per 100 lb body weight rather than

the theoretical recommendation of 40 to 60 mg per 100 lb

1

38

body weight, in order to maintain consistently high

fertility. Boume attributed this to possible factors which

interfere with the absorption of manganese from ingested

food - one such factor being the calcium and phosphorous

content and the calciumlphosphorous ratio of the ration. He

further suggested that the dramatic reduction in Brucella

abortion in vaccinates, observed by Herrod-Taylor (1966) as

a result of feeding a phosphate rich supplement, may have

been due to a "conditioned"manganese deficiency.

Working under experimental conditions Rojas et al.

(1965) found that cows deficient in manganese, although

exhibiting regular estrous cycles, required an average of

four services compared with twofor the controls. AlI

calves born to deficient dams were deformed showing enlarged

joints, stiffness, twisted legs and a general physical weak-

ness.

AlI these results appear to be fairly consistent one

with another and with the early suggestion of Hignett (1941).

However, another view has been introduced by Havre and Dynna

(1961) in Norway, as reported by Dawson (1967). Manganese

deficiency had appeared over 6-7 years in young cattle on

one particular heavily limed farm. It was found that the

manganese content of the grass and hay was just within

normal limits but that its copper content at 2-3 p.p.m. was

very low. Feeding extra copper alone was much less effective

as a cure but a copper and manganese supplement was very

.i

\, .'

39

successful.

"Lack of Manganese" appears to produce ovarian

quiescence, infertility, abortion, poor corpus luteum

formation, bone weakness and deformity such as fetlock

knuckling in young stock. According to Dawson (1967) such

findings have also been reported from Eastern European

countries where Richter and Schroder (1964) associated them

with very low hair manganese content. Rasbech (1968) and

Krolak (1968) as reported by Mc Clure (1970), found that

low levels of dietary manganese caused subestrus or anestrus.

Rasbech found that, while 20 p.p.m. were adequate for

growth, aIl of the Il heifers failed to show heat.

f. Other MineraIs

Among other mineraIs essential for the general

welfare of the cow, deficiencies or excesses of copper,

iodine, cobalt and fluorine have been shown to be implicated

in reproductive disturbances.

The production of dead or nonviable goitrous calves

indicates an iodine deficiency in the ration of pregnant

cows. Schmidt et al. (1965) fed potassium iodide supplement

to 52 infertile buffalo cows in Egypt, and compared the

results with a control group along with another group

receiving a calcium, phosphorous and manganese- supplement.

A fourth group received both supplements and gave best

pregnancy results, but the group receiving only iodide did

( ,

40

nearly as weIl, whereas the other supplement alone was less

effective. This seems to indicate that iodide was the main

deficiency involved.

Copper deficiency has long been loosely implicated

with infertility, especially anestrus in cattle, but there

have been some reports of cattle breeding normally while

showing low blood or liver copper levels and systemic copper

deficiency symptoms (Dawson,1967'). The explanation of this

inconsistency probably lies in the complex relationships

of this trace element with others. Such findings indicate

that while it may be convenient to consider dietary

constituents under various headings it is always important

to recall the existence of interactions between pairs or

indeed complexes of different elements.

In Queensland, Australia, Donaldson et al. (1964)

obtained a significant improvement in pregnancy rate as

against controls in ranch heifers receiving a single

injection of 400 mg copper glycinate (p(0.05). Other work

in England, Munro (1964), attributed abortion and returns to

service as weIl as anestrus in cattle to copper deficiency.

Either copper injections or the feeding of anti-teart cake

proved effective counter-measures. Blood levels here were

no lower than 0.08 mg% (Dawson,1967).

Fluorine is present in varying amounts in feeds of

livestock, but it's essentiality for animaIs has not been

established. Systemic symptoms of fluorine poisoning has

41

been described, however, Van Rensburg and De Vos (1966)

reported field evidence indicating that chronic subclinical

fluorine poisoning induced by feeding 5 to 12 p.p.m.

fluorine in drinking water for more than one year caused

anestrus, a reduction in conception rate and a marked drop

in pregnancy rate.

4. Vitamins

a. General

Under normal conditions, natural feeds furnish most

vitamins or their precursors in adequate amounts. Ruminants,

such as the cow, are fortunate from a standpoint of their

vitamin supply since they are capable of synthesizing aIl

of the B vitamins and vitamins C and K in adequate

quantities. As a result, the need for dietary sources of

the above named vitamins has not been established for

animaIs on conventional rations. However, the adequacy of

vitamin intakes should be verified under certain conditions,

such as when forage is fed in limited amounts or is low in

quality, when sun-cured hay or exposure of animaIs to

sunlight is limited, and when milk replacers for young

calves are relied on extensively (Anon.,197l).

MaternaI transfer through the uterus to the fetus is

a critical source of vitamins for prenatal growth and

viability during the first weeks after birth, so that rations

fed to dairy cows should therefore include feeds that

contain ample carotene (vitamin A) and vitamin D.

~.

42

b. Vitamin A

Vitamin A deficiency in cattle or an inadequate

intake of carotene resu1ting in a depletion of the anima1's

reserve results in b1indness, (especially night blindness),

edema. lower milk production, and reproductive disturbances.

On Many feeding regimes aIl that would be necessary for

deficiency to arise would be over-sunning or weathering of

the hay to be fed before it was stacked. However, the

like1ihood of such deficiency under tropical conditions is

very remote. as forage is general1y not preserved.

In early work, Guilbert and Hart (1935) found that

rations deficient in carotene caused impaired reproductive

perf'ormance in beef cows. Marked vitamin A deficiency has

affected the reproductive function of dairy bulls by

restricting their ability to MOunt and deliver semene The

extent to which this function is impaired or retarded

depends on the severity of the deficiency (Hodgson ~ al.,

1946) •

Ghannam et al. (1966) and Ghannam et al. (1969) -- --:round that vitamin A dep1etion inhibited spermatogenesis

and reduced the diameter of the vasa deferentia. Lesser

degrees of avitaminosis A (plasma vitamin A leve1s of 5

to 10 ug/lOO ml for 7 months) increased the proportion of

deformed spermatozoa. particularly when bul1s were subject

to transport stress and deprived of drinking water

(Jaskowski ~ al., 1966). Further work by Kupferschmied

\ '.

(

4J

and Rehm (1968), indicated that a single dose of an

emulsifiable water-free vitamin preparation (vitamin A,

2,500,000 - J,OOO,OOO I.U.; Vitamin DJ ,J75,000 - 450,000 I.U.;

Vitamin E, 250 - JOO mg) significantly improved the quality

of sperm and reduced the proportion of still-births.

Long-time feeding of sub-optimal or deficient

carotene rations has detrimental effects on the structures

of certain tissues and organs, resulting in a loss of

reproductive efficiency and viability (Byers et al., 1956).

Later-generation animaIs were also affected. In the second

generation low-carotene bulls showed degeneration of the

seminiferous tubules, reduction in interstitial tissue and

Le'ydig cells, and reduced spermatogenesis. Second­

generation cows showed marked loss of reproductive efficiency,

frequently aborted or produced still-born calves too weak

to survive.

Nicholson and Cunningham (1965), working on the

vitamin A deficiency problem in housed beef cattle heavily

barley fed, found that over 50% retained the placenta (and

smaller numbers aborted), and the birth of several dead or

weak calves resulted, unless the individual intake reached

at least 50,000 I.U. vitamin A daily. They also found thst

vitamin E, if fed, affected the animaIs' ability to use

vitamin A without assisting reproductive performance.

More recently Meacham ~~ al. (1970) found that in

-, . .;

44

beef cows conception rates were increased from 81.1% to

90.2% (P<:O.OS) and calf surviva1 increased by supplementing

the ration with vitamin A (16,000 I.U. during late gestation

and 40,000 I.U. per head per day during ear1y lactation).

A review by Dawson (1967), indicates that there seem

to be much attention being paid in Germany to obtain well­

based diagnosis of vitamin A deficiency as a cause of herd

breeding problems, based on forage sample analysis. Aehnett

and Konermann (1961) considered it was the commonest cause

of breeding problems encountered in spring, and Ehrlich

(1962) produced similar evidence. Ehrlich recommended a

single injection of 1 million units vitamin A, and dai1y

B-carotene requirements as SO mg for body maintenance, 2S mg

per litre of milk and 200 mg to maintain a pregnancy.

Circumstantial evidence was also produced by Geyer (1961)

that retained placenta was characteristic of the late winter

syndrome in Germany. In 300 cows when receiving 1ess than

half of theoretical requirement, neonatal deaths reached 6%

and retained placenta affected 13% of cows.

Observations out of Israel reveal that apart from

problems of retained fetal'membranes encountered in dairy

cows due to subnormal blood levels of both vitamin A and

carotene, there was also increased incidence of metritis.

Injecting cows with 1 million units of vitamin A, 7 - 10

days before calving date decreased the incidence of

metritis as weIl as retained fetal membranes (Danieli,1968).

--)

f

\

45

c. Vitamin D

The important role played by vitamin D in preventing

disease and promoting the efficient utilization of calcium

and phosphorous by calves and ~ung cattle is now well

established. Calves born to cows maintained for a consider-

able time under vitamin D deficient conditions May have a

decided rachitic appearance and possibly a lowered Mineral

content of the bones.

As far back as 1938, Wàllis reported disturbances of

breeding efficiency of cows previously without any problemso

None of five Holstein cows showed estrus during vitamin D

deficiency, but there was no clear indication whether this

condition should be attributed to lack of vitamin D per ~

although the rations used c~ntained adequate amounts, in

good ratio, of calcium and phosphorous.

Subsequently, Abrams (1952a) concluded that the

evidence for deleterious effects of hypovitaminosis D on

growth and reprOductive phenomena was sound, and criticized

the conclusions of Hignett and Hignett (1952) about the

effect of phosphorous deficiency as such on bovine fertility,

since the status of vitamin D in British cattle, especially

in winter, was doubtful. Under tropical and subtropica~

conditions it seems MOSt unlikely that a deficiency of

vitamin D will ever be a problem in grazing cattle; however,

in interpreting data from the more temperate regions it May

be weIl worthwhile to consider the potential confounding

( \ ....

(

46

effects of vitamin D.

A recent report by Ward ~t al. (1971) indicates that

first observed estrus occurred earlier after .parturition in

cows which received supplemental vitamin D (P (.06), than

in those not receiving vitamin D. The interval between

parturition and subsequent conception averaged 37 days

shorter for cows supplemented with vitamin D than for cows

not receiving it, thus, shortening calving interval more

than a month.

C. EFFECT OF FEEDSTUFFS

Following the recognition by AIder and Trainin (1961)

of reproductive disorders in cattle grazing on lucerne

(Medicago sativa), Thain (1965, 1966, 1967) reported field

evidence that cattle grazing on subterranean clover

(Trifolium subterranean var. Mt. Barker) dominant pastures

in Tasmania were less fertile than cows grazing grass­

dominant pastures. Additional field evidence was provided

by Lotan and AIder (1966) from problem herds in Israel.

These authors found that the clinical signs were irregu­

larity of estrous cycle length ( 17 and 23 days) and a

lowering of the conception rate. The lucerne contained

25 ug estradiol equivalent jkg and the daily intake was

equal to or greater than 125 ug/day.

A close association between the feeding of Kale

(Brassica oleracea) and fertility has been reported

47

(Reed, 1961, Melrose and Brown,1962). In a controlled

experiment, Melrose and Brown indicated that there was a

lowered conception rate to first service and longer return

intervals after failures (average, 38.8 days vs 21.6 days)

in Friesian heifers fed Kale as opposed to controls. David

(1965) has provided additional evidence suggesting that

goitrogens in Kale may be responsible for infertility.

More evidence has continued to accumulate indicating

that over-mature grasses are not able to maintain body

weight, lactation, and reproduction. This could be quite

common in areas where drought is common, or periods where

nutritional stress occur annually, such as the tropical and

subtropical regions of Australia, Africa and the Americas.

This over-mature forage is of low digestibility and provides

a low intake of energy. ·It also contains insufficient

protein, mineraIs, especial1y phosphorous, and carotene

(Suther1an~ 1959). Thus Armstrong ~ Al. (1968) has shown

that beef cows lost weight during the dry season and gained

weight during the wet season in north-western Australia.

In feeding experiments, supp1ementing the dry pasture with

protein ri ch cotton seed meal they were able to reduce

weight losses of breeding cows from 47% to 0% and increased

the number of calves borne . Simi1ar results have been

obtained by Sparkle and Lamond (1968).

Immature pasture is not always able to maintain

body weight, lactation and high fertility in dairy cows

l. (Mc Clure,196l, 1965a,b). It appears that the quality of

the feed as weIl as insufficient intake is important

48

(Mc Clure, 1968b) for a comparable restriction in the intake

of dairy meal did not lower first service pregnancy rates.

Working with beef heifers, Buchanan-Smith ~ al.

(1964) found that those transferred to an all-concentrate

ration ad libitum were mated earlier than those left on

silage plus 1 pound mi10 and 1 pound cotton seed meal /day.

Thus it appeared that the al1-concentrate ration has a more

prompt influence on estrous occurrence than a roughage

ration.

Manufactured feeds and by-products of industry can

vary in composition and may be inadequate for reproduction.

A good example is sugar-be,et pulp which is markedly deficient

in phosphorous (A1derman, 196).

D. CAUSES OF NUTRITIONAL Ir~ERTILITY

Three aspects of the pathogenesis of nutritional

infertility have been reported.

a. Lactational Stresses

The opinion is frequently expressed by ~armers and

veterinarians that high-yielding dairy cows do not conceive

as easi1y as those producing at a lower level. Early

workers in this area have expressed differing views, some

indicating that lactation has an effect simi1ar to that of

49

growth rate, but to a greater degree. Lewis and Horwood

(1950), Mc Taggart (1961), Donaldson (1962), and Hooper and

Letts (1962) have indicated that lactation is a contributing

factor toherd infertility. However, Eckles (1929) and

Currie (1956) failed to find evidence that lactation

influenced reproduction. Meyer (196J), as reported by Mc

Clure (1970), in a review, has found that the available

evidence was cOnflicting and confused.

According to Mc Clure (1970) considerable interest

in lactation affecting fertility is evident in reports from

Europe. Nevertheless, subject to the limitations of

statistical survey data, many of the recent reports indicate

a significant, though sometimes small, depressant effect of

lactation on fertility.

Hewett (1968) found that the incidence of repeat

breeders among 16,000 cows on 1500 farms in Sweden was over

10%. The affected cows gave significantly more milk (84.4 kg)

during the first 120 days of lactation than the controls. the

difference was greater (108.0 kg) in cows which had one

previous lactation.

Evidence supporting the hypothesis that high producing

cows are less fertile than low producing cows has been

reported by Horvath (1966), Steele et al. (1967), and

Varejcko (1968). Varejcko found that the conception rate

to first service decreased from 69.2% for heifers to 40.8

46.7% after the second to the sixth calving, and the

insemination index from 1~48 to 1.94 - 2.22. The index

'-1 . ,

(

50

increased from 1.37 to 2.5 as milk production increased

from under 2000 to 5500 kg and was 2.25 for higher yielding

cows.

The practice of suckling is known to increase the

length of the interval from calving to the post-partum

estrus in cows (Clapp, 1937; Wiltbank and Cook, 1958;

Aliseihov, 1964; Saiduddin et al., 1967). Aliseihov found

that the interval in nurse cows was 108 days compared with

the 60 da ys of the cows in the dairy herd. It is not clear

whether this inhibition of reproduction is due to physiologi­

cal responses to suckling or is the result of increased milk

yield shown to occur as the result of suckling (Fatel and

Fatel, 1963).

b. Body Weight Change

For some time it has been recognised that body weight

is related to fertility. Reid ~~. (1964) have shown that

the rate of weight gain of heifers affected.pubescence and

that puberty depended largely upon body weight. Nutritional

stress super-imposed on lactational stress has been known

to affect fertility. The loss of weight that occurred in

beef cattle in the dry season was associatedby Kidner

(1966) and Armstrong ~ al. (1968) with low fertility. Both

the body weight and fertility recovered when the summer

rains came and feed quality and quantity improved (Donaldson,

1962). General observations with beef cattle having their

first calf at foot are that such animaIs have the lowest

51

body condition score and lowest fertility of any class of

animals in beef herds. Sparkle and Lamond (1968) observed

that lactating heifers needed to be at least 100 pounds

heavier than they had been the previous year when they were

first mated in order to obtain satisfactory pregnancy rates.

Similar body weight and fertility observations have been

described when considering plane of nutrition (Turman ~ ~.,

1964; Reynolds ~ ~., 1964; Hight, 1968).

The high-producing dairy cow in the first month or

two of lactation is a special case of under-nutrition as

she is usually in a negative energy balance ev en when

offered liberal amounts of an adequate diet. Wh en maintained

wholly on pasture a further complication arises because,

although she may or may not be losing weight, she could be

on the borderline of deficiency of any number of nutrients

from day to day. In fact, the relation between supply of

nutrients and reproductive performance in grass farming

systems is a special and difficult problem (Lamond, 1970).

Problems of this nature, seem to occur in pasture­

fed dairy cows in New Zealand and New South Wales, Australia

(Mc Clure, 1961, 1965a, b). Cows fed on lush young grass

or forage oats may lose excessive amounts of body weights

(between 5 to 10% of their immediate post-calving weight)

by the time of mating and fa il to hold to service. Supple­

menting the pasture with 10 to 14 pounds hay/cow/day (or 12

pounds dairy meal, Mc Clure, 1970) decreased the weight loss

i \.

(-

52

and significant1y increased the fertility. Hutton (1963)

observed that the intake of pasture did not reach its

maximum until five months after ca1ving, and that cows in

early lactation were in a state of negative energy balance

and 10st weight. Such information emphasizes the importance

of the qua1ity of the feedstuffs fed at the particular

periode The weight of dry cows fed simi1ar pasture (Hutton,

1963) and 1actating cows fed dairy mea1 at high planes (Mc

C1ure, 1970) did not fa11. This association between 10ss of

body weight during ear1y lactation in dairy cows and 10w

first service pregnancy rates has also been confirmed by

King (1968) who found that 78% of cows increasing in body

weight he1d to first service compared with on1y 16% of the

cows 10sing weight.

c. Blood Ana1ysis Criteria

The measurement of various blood constituents for

examp1e, protein, calcium, phosphorous, hemog10bin, vitamin A

etc., can give an indication of nutritiona1 deficiencies or

previous disease conditions in the cows.

B1ake1y (1965), quoted by Mc Clure (1970), reported 10w

b100d-glutathione and cholesterol leve1s and thyroid secretion

rates in infertile Hereford heifers fed 4.2 pounds TDN/day.

Mc Clure (1965b) observed that, at the time of mating,

the b100d-glucose 1eve1s of infertile dairy cows fed on

1ush pasture were fa11ing and were lower than those of

fertile cows which were rising. Later,he observed (1968b,

(

5)

1970) that the blood glucose levels of cows fed on forage

oats (Avena sativa) were lower than those cows fed on

similar diets but supplemented with energy-rich concentrates,

and that cows fed low levels of either type of diet had

lower levels than cows fed at high planes. He suggested

that hypoglycaemia might be the primary biochemical les ion

occurring in lactating cows fed on lush pasture or forage

oats and losing "excessive" amounts of body weight at the

time of mating. Administration of insulin ta lactating cows

for three or four da ys before expected estrous periods

decreased the blood-sugar levels and suppressed estrus or

depressed the pregnancy rates of cows'mated within two days

after the last dose (Mc Clure,1968a). In mice, acute fasting

and insulin both of which caused hypoglycaemia, and adminis­

tration of 2 - deoxy - D - glucose, a glu~ose metabolic

inhibitor, caused lesions which varied from embryonic death

to failure of ovarian follicular development (Mc Clure,

1966, 1967a, b).

In Europe, Arzumanjan and Dorotjuk (1964) observed

that the blood-protein coefficient, blood-sugar, and semen

albumen contents were higher in Black Pied cows which

conceived to insemination than in those failing to conceive.

They also observed that the service periods~of the cows

yielding ),000 kg to 5,000 kg of milk were longer than those

of cows yielding up to ),000 kg, again suggesting a

lactational stress factor affecting fertility.

In blood analyses conducted on 1,333 dairy cows,

hemoglobin values below 9.8 gm/lOO ml were associated with

anestrus and repeat breeding in 530 cows while the 803 cows

with normal reproductive performance had average hemoglobin

of 10.67 gm/lOO ml (Hansel, 1968 reported by Morrow,1970).

Low blood content of inorganic phosphorous has also been

associated with infertility (Morrow, 1969, 1970).

III. OBJECT OF RESEARCH

A review of the Literature has indicated the many

nutritional problems that can affect fertility.

The object of the research as reported in this

thesis wasl

1. To investigate the possible relationship between

infertility in dairy cattle and nutritional

criteria.

2. If nutritional infertility did exist, to determine

whether there was any relationship between the

condition observed on farms in the Province of

Quebec, and on farms in Trinidad with cattle of

similar origin and breed.

55

56

IV. DATA SOURCE AND METRODS

A. QUEBEC PROVINCE

1. General

Eleven dairy farms enrolled on the Dairy Herd Analysis

Service (D.H.A.S.) program of Macdonald College considered

as representative of farms on the program were selected for

data collection. This selection was done with the assistance

of Mr. Orance Mainville, who actively participated in the

study initially, and the D.H.A.S. field supervisors. These

farms were located mainly in South-Western Quebec and lie

within an approxima te 60-mile radius of Macdonald College.

Mr. Mainville and the D.H.A.S. supervisors acted as

interpreters (majority of farmers were french speaking) and

assisted in collecting forage, grain and blood samples and

any further descriptive information relative to the farm

operations. AlI herd owners were keen to co-operate and

the period of collection of aIl samples was April - May 1971.

2. Sampling Procedure

a. Hay Samples

Hay samples were obtained from baled hay by using a

"Penn State" forage sampling devicel • Sample cores were

randomly taken by drilling into the exposed ends of about

1 Scientific Systems Inc., State College, Pa., U.S.A.

\

57

6-8 baIes. The samples were then emptied into a pDlyethy­

lene bag which was then sealed by folding the top over

several times and stapling across the fold and an

identification card listing the farmer and number of sample.

b. Corn and Grass Silage.

Samples of either corn or grass silage as were avail­

able on the respective farms were collected either by drilling

or taking several handfùls from the exposed surface of the

silage. Any spoiled silage was removed before sampling. Cores

or handfuls were taken at random from about six spots from the

exposed face of the silo, and placed in the same type of

polyethylene bags as the hay samples, sealed very tightly to

minimise loss of moisture from the samples, and identified

accordingly. Silages were then dried on the same day.

c. Grainsoor Concentrates

Representative samples of grain mixtures or concen­

trate mixtures were taken and placed in similar polyethylene

bags, sealed, and identified in similar manner as for hay

and silage.

3. Blood Collection and Microhematocrit Determination

Herd size varied from 26 to 54 with a mean of 32

Holstein cows. Ten cows were selected from each he rd for

blood sampling.

Blood samples, for serum and microhematocrit analysis,

were collected by venipuncture from the external jugular

vein of cows into clean, dry 127 x 16 mm vacutainer blood

58

collection tubes in 10-12 ml amounts. Hypodermic 16 guage,

1" sterile monoject needles were used for venipuncture.

Immediately after collection microhematocrit heparinized

capillary tubes measuring 75 mm x 1.0 mm were filled with

blood between two-thirds to three fourths capacity by

capillary attraction, the outside wiped off and the opposite

end of the capillary tube sealed with rubber caps. The

blood samples were then allowed to clot, the sera separated

by centrifugation at 2260 x G for 20 minutes and kept

frozen until analysed.

Packed Cell Volume (PCV) was determined by centri­

fugation (using an International Hematocrit centrifuge) of

the sealed capillary tubes at 2260 x G for JO minutes and

the results read off using an International Microhematocrit

Reader.

B. TRINIDAD

1. Location and Climate

Trinidad is the southernmost of the West Indian

islands - an archipelago stretching from the tip of Florida,

in the United states of America to the north eastern coast

of Venezuela in South America. The island lies at 100 JO'

north latitude and 61 0 15' west longitude. The distinguish­

ing feature of climate is rainfall; there are marked wet

and dry seasons. The former extends from May to December,

interrupted by a two or three week dry period in September

59

or October, and ~ dry season from January to April. The

mean annual rainfal1 varies from 50" (127 cm) to 75"

(190.5 cm). The climate is almost constant throughout the

year - a1ways hot and humid - but is tempered by the

breezes of the Atlantic. Humidity is high, usua1ly above

80%. The average annual maximum and minimum temperatures,

and diurnal variations are given in Table 1.

TABLE 1

AVERAGE TEMPERATURE IN TRINIDADI

TEMPERATURE

FAHRENHEIT CENTIGRADE

Highest Maximum Temperature 950

350

Lowest Minimum Temperature 600 170

Average Maximum Temperature (Annual) 880 310

Average Minimum Temperature (Annua1) 720 22.20

Maximum Diurnal Variation 270 150

Minimum Diurnal Variation 50 30

Mean Diurnal Variation 170 100

1 . Source: Government Meteorologica1 Station, Piarco

60

Thirty farms (approximately 20 acres each) were

selected for this investigation and these were considered

representative of a wide cross section of the established

farms with management varying from good to poor. Sixteen

of these farms were located at Wallerfield situated in the

north, eight at Carlsenfield and six at Esmeralda both

located in the central parts of the island. In addition

the Government station at Centeno, located in the north

and comprising both a Holstein herd and aherd of Holstein­

Zebu cross were used in the study.

The period of collection of aIl data and samples was

between June 15th and July 31st. 1971.

2. Sampling Procedure

a. Pasture Grasses

Samples of developed pangola grass (Digitaria

decumbens,Stent.) pastures were cut by hand from 9 inch

(22.9 cm) squares at about 10 yard (9.1 m) intervals over

a large representative area of the grazing paddocks. Wh en

about 3 pounds (1.4 kg) of pasture had been obtained this

was placed in polyethylene bags and sealed very tightly

and identified. Samples of Napier grass (Pennisetum

purpurem) grown on some farms, were taken by cutting repre­

sentative samples and treated exactly like the pangola

grasse Each sample was then frozen at _200 C until ready

for grinding.

61

b. Concentrates

Representative samp1es of a commercial dairy ration

(Table 2) as used on the farms were sea1ed in polyethylene

bags and stored for transporting to Macdonald College. As

different commercial feed companies prepared rations from

the same formulation it was necessary to take samples from

each farm to observe variation in production since no

controls exist for feed quality in the island.

TABLE 2: DAIRY RATION COMPOSITION1

Ingredient % Protein ~ Fibre Crude Digestible %

Coconut oil meal 27 5.7 4.9 2.9

Soy-bean oil meal 10 4.4 ].8 0.6

Wheat middlings JO 5.0 4.1 2.9

Brewers dry grain 10 2.] 1.7 1.6

Citrus meal 12.5 0.7 0.4 2.0

Molasses 7.0

MineraIs J.52

Total 100 18.1 14.9 10.0

lSource: Dr. J.G. Davidson, Ministry of Agriculture, Trinidad

2Consists of 1% dicalcium phosphate, 1% Na Cl., 0.5% limestone, 1% mixture of trace elements and vitamins.

TDN %

21.0

7.8

20.1

6.2

9.7

].8

68.6

62

3. Blood Collection and Microhematocrit Determination

Blood samples were collected from aIl animaIs above

1 year old and up to 7 months pregnant. A total of 472

animaIs were sampled on the 30 farms with a range of 10 -

21 and a Mean of 16 animaIs respectively. On the Government

Station 48 purebred Holstein and 112 Crossbred Holstein-

Zebu animaIs were sampled.

Blood sampling for serum and microhematocrit analysis

was basically the same method as previously described for

Quebec, however, the heparinized capillary tubes used

measured 32 mm x 0.8 mm and were sealed by a plug of clay.

Packed Cell Volume (PCV) was determined by

centrigufation (using a Drummond Microhematocrit Centrifuge)

of the sealed capillary tubes at 14,000 x G for 2 minutes

and the results read off on a Drummond Microhematocrit

Reader.

Sera separation was as previously described. Samples

were kept frozen and were subsequently packed in dry ice,

and along with forage and concentrate samples, were air

freighted to Macdonald College where aIl analyses were

carried out.

C • FEEDING AND MANAGEMENT

1. Quebec

The general practice on MOSt farms is to keep animaIs

on pastures, day and night, except when being milked, from

,.:

63

late Spring to early Fall and supplementing with grains

according to production and the quality of the available

pasture. For the rest of the year animaIs are housed and

fed hay, silage and grains according to production. Since

each herd involved in this study is enrolled on the D.H.A.S.

program, grain feeding recommendations are usually based on

the quality and amount of forage fed.

2. Trinidad

On aIl the farms involved the' dairy cows are kept on

permanent pastures of pangola grass day and night, except

during the periods of milking. It is generally accepted

that grazing should provide enough energy for body main­

tenance, and in addition, a commercial dairy ration is fed

according to milk production at the rate of 4 pounds of

concentrate per 10 pounds of milk produced (1.8 kg per 4.5 kg).

During the dry periods, or periods of inadequate pasture

growth a basal ration of 2 pounds (0.9 kg) of citrus Meal is

usually fed to augment the pasture supply, or where available

zero grazing of Napier grass is substituted.

In MOSt cases adequate shade is provided in each

paddock, and rotational grazing is practiced to control

forage quali~y as weIl as to interrupt life cycles of

internaI and external (ticks) parasites. In addition

animaIs are sprayed within 7-14 days with Sevinl in order

lSevinll-naphthyl-N-methyl carbamate - sprayed on as suspension

(

64

to control tick infestation.

D. ANALYTICAL METRODS

1. Preparation of Samples

AlI samples were weighed then dried at 650 C overnight

in a forced air oven after which they were passed through

the medium (1.7 mm diameter) size screen (equivalent to

12 mesh U.S.B.S.) of a Raymond Laboratory Hammer Mill. AlI

hays, silages and grain mixtures were treated in the same

manner, however, the commercial concentrate preparation only

received grinding as it was previously air-dried.

Each ground sample was then thoroughly mixed, placed

in plastic bags and sealed tightly.

2. Chemical Analyses

a. Forages and concentrates

AlI forage and concentrate samples collected were

analysed for dry matter by the vacuum drying method of the

A.O.A.C. (1965) since the forced air oven drying was

considered as only 90%. The cellulose content of aIl samples

was determined by the method of Crampton and Maynard (1938) as

modified by Donefer et al. (1960). Crude protein analysis

was conducted according to the A.O.A.C. (1965) macro-kjel­

dahl Methode Calcium analysis was determined according to

the A.O.A.C. (1965) atomic absorption spectroPhotometryl

on wet ashed samples. Phosphorous was determined according

lSp 90A Atomic Absorption Spectrophotometry - UNICAM

to the A.O.A.C. (1965) method for phosphorous in feeds

using a spectrophotometerl •

b. Blood Analysis

Serum calcium was determined by atomic absorption

spectrophotometry2 and serum inorganic phosphorous analysis

was by the method described by Simonsen et sl. (19~6).

J. Procedure to evaluate the Energy Content ofl

a. Forages

Nutritive Value Index (NVI) as developed by Crampton

et al. (1960) is defined by the following formulai

NVI = Relative Intake (RI) x % digestibility of energy.

A laboratory method developed by Donefer et al. (1966)

whereby NVI could be predicted from dry matter disappearance

(DMD) by incubation of a forage sample in an aqueous solution

of pepsin - HCl, was used in this study.

NVI was calculated by the following prediction

equation:

NVI = -0.75 + 1.60 X

where

x = per cent DMD

IBausch & Lomb Spectrop.hotometer.

·2SP 90A Atomic Absorption Spectrophotometry - UNICAM

A.O.A.C. (1965).

This evaluation procedure developed by Donefer and

his associates now serves as the basis for the Macdonald

College Feed Testing Program and is used to estimate the

"Quality Code" or estimated net energy(ENE) content of a

forage.

66

The system of assigning Quality Codes to indicate the

estimated net energy content of forages is being followed

by Many Dairy Herd Improvement Associations in the United

States, and was introduced by the New York State program.

The procedure used by the Macdonald College Feed

Testing Program was also used to predict the ENE content of

aIl forages used in this study.

NVI = Quality Code = ENE = megacalories (Meal) per

45.4 kg DM or therms

per 100 lb

In the Quebec herds the ENE consumed by each animal

was based on calculations from the actual amount of forage

fed - on a dry-matter basis - to a 1000 pound (454 kg) cow,

adjusted according tm the body weight of the individual

animal.

However, in Trinidad, the intake of pasture (pangola

grass) by individuals could not be determined and presumed

intakes were assessed from known dry matter requirements of

2.5 pounds (1.1 kg) of very liberal feeding of good roughage

per 100 pound (45.4 kg) body weight (Morrison, 1959), and

based on a report from Puerto Rico where cattle grazing on

r "-. '.

67

pangola grass consumed an average of close to 2.5 pounds

(1.1 kg) of dry forage per 100 pound (45.4 kg) of liveweight

(Vicente - Chandler ~al.,1964).

b. Concentrates

In the Feed Testing Pro gram at Macdonald College

calculations of Total Digestible Nutrients (TDN) of concen­

trates are based on laboratory cellulose analysis ex~ra­

polated from a regression equation arrived at from values

taken from N.R.C. Feed Composition Tablesl • Wh6le soy-beans,

beet pulp and molasses are exceptions to this relationship.

A high correlation exists (r = -.97) between crude

fiber (cellulose) and TDN, and this TDN content was calcu­

lated from the following prediction equation (for Quebec

concentrates), as used bythe Macdonald Feed Testing Service.

y = 83 - 1.4 X

where

X = per cent ~ellulose) crude fiber

Due to the inherent difficulties of the crude fiber

analysis - both time consuming and empirical aspects - plus

the fact that cellulose determination is a routine analysis

in our laboratory, and the close relationship between

cellulose and crude fiber, it was decided to use cellulose

as an indicator of crude fiber. WeI ton (1968) observed

correlation coefficients between crude fiber and cellulose

varying from 0.91 to 0.99.

lFeed Composition data from N.R.C. Nutrient Requirements of Dairy Cattle 1971. National Academy of Sciences, Washington D.C

/

'-

68

TDN values for Trinidad were extrapolated on a similar

basis (Fig. 1), however, the regression line was lowered to

be consistent with the TDN values reported for the Trinidad

Dairy Ration (Table 2) in order to prevent inflation of the

readings of various feed compositions.

Since estimated TDN values for concentra tes closely

approxima te ENE values (Table 3) - in fact at 7% crude fiber

TDN and ENE were the same - it was decided to assume that

ENE of the grain mixture was the same as predicted TDN.

Based on the practical orientation of this study it

was considered that aIl assumptions used were valide

TABLE 3' ESTlMATED TDN AND ENE CONTENT OF MANUFACTURED DAIRY FEEDSI •

Maximum Crude Estimated Estimated Fiber as Guaranteed TDN Net Energy

1

~ ~ ~thermsLcwtl 4.0 79.5 81.3 5.0 78.0 79.1 6.0 76.5 77.1 7.0 75.0 75.0 8.0 73·5 72.8 9.0 72.0 70.9

10.0 70.5 68.3 Il.0 69.0 66.6 12.0 67.5 64.6 13.0 66.0 62.5 14.0 64.5 60.4

Source. Dairy Feed Manual College of Agriculture, The Pennsylvania State University.

Figure 1. Relationship between Cellulose content (%) and TDN •

85

80

75

65

60

\, '\ , " , , ,

" , , , \

" , , , \ " \

\

"

•

,

Trinidad

" , \

'\ \ , \ " " " , , ". , ,

'\ , , ,

" "

N.R.C.

69

" 55~----------~------~\~~~---------~~-------10 20 30

Cellulose Content (%) Source: Feed Composition data from N.R.C. Nutrient

Requirements of Dairy Cattle 1971.National Academy of Sciences, Washington D.C.

70

4. Other Data

AlI other information such as age, previous production,

lactation sequence and calving interval for the Quebec herds

were obtained from the D.H.A.S. records at Macdonald College.

In Trinidad, records were obtained from individual

cow records retained on the respective farms. Records of

bulls' fertility were obtained from the Government

Artificial Insemination~.I.) centre. Body Weight of each

animal was determined by the use of a Purina girth tapel •

E. STATISTICAL ANALYSIS OF DATA

For identification purposes the eleven herds in Quebec

will be referred to by the letters A to K inclusively. For

the thirty herds in Trinidad the numerals 1 to JO will be

used. However, the two Government herds (Trinidad) will be

referred to as Crossbred and Purebred Holsteins.

Means and Standard Error for aIl parameters, and

Simple Correlations between services per conception and

calving interval and aIl other parameters examined. were

calculated according to the method described by Steel and

Torrie (1960).

In this study unequal subclass frequencies causedthe

different classes of effects to be non-orthogonal. Thus

1 Made according to United States Department of Agriculture specifications.

f \

71

it was necessary to consider aIl effects simultaneously in

order to free them from entanglement. The method of analysis

used was that of least squares estima tes as outlined by

Harvey (1960).

The IBM 1620 Digital Computer was utilized to execute

the calculations of statistical analysis described above.

72

v. RESULTS AND DISCUSSION

1. Incidence of Infertility

Current economic conditions dictate high milk

production and breeding efficiency for profitable dairying.

Low fertility is widely recognised as one of dairy manage­

ment's major problems. While much progress has been made

in improving dairy cattle fertility through disease control,

breeding problems have surpassed udder trouble and rank

second to low milk production as cause for culling,

increasing from 17 to 22% of aIl culled cows during 4 years

(Bonewitz et al., 1966-71). Services per Conception and

Calving Interval have been the criteria used as the index of

infertility.

a. Services per Conception

Table 4 indicates the incidence of infertility of

Cattle surveyed in Trinidad based on actual calvings.

These data indicate that the overall fertility rate was low

when compared to the first servié-a acceptable fertili ty

rate of 55% as proposed by Zemjanis (1965). However, it is

interesting to note the higher first service calvings on

the Trinidad Herds (Jrown Lands Herds) of 47.7% as compared

to the herds maintained on the Government Station, 34.0%

for the Purebred Holstein and 39.3% for the Crossbred

Holstei~Zebu herd. The values for the Government herds

'1

" .

.. --.--..., /"'----

Table 4. The incidence of infertility of cattle in Trinidad.

Fertility Index

First Service Conception rate in per cent.

Per cent of animals re­quiring 3 or more services.

Total con­ceptions in­vo1ved.

Government Station Crossbred No. Holstein

(a) heifers 31.3 (b) cows 45.6

Overall 39.3

40.2

(99) (125) 224

22LJ.

27.8 3LJ..9 34.0

46.1

No.

(18) (123) 141

141

Other Herds Holstein

(CrJ2wn Lands)

47-7

29.3

870

'"'1 \N

~

(-, !:._ f

closely follows the picture observed in Jamaica, from 25

herds whose first service conception rate was JJ%

74

(Zemjanis, 1965) and from J6 Friesians in Uganda where a

first service conce~tion rate of JO.5% was reported (Trail

and Marples, 1968). Pelissier (1972) analysed the breeding

records from 24 commercial dairy herds within California

and reported an average first service conception of 44.2%.

The Trinidad (Crown Lands) herds compare favourably with this

finding and,in fact represent a slight1y better picture.

In Tables 5, 6 and 7 are set out the number of

services required per conception for each herd in Quebec,

the Trinidad Herds (Crown Lands Herds) and the Government

Herds respective1y. If we accept the criterion of Zemjanis

(1965) of 1.8 services per conception then only herds

A, B, F and K or 4 of the Il or J6.4% of the Quebec herds,

and herds l, 5, 12, 25 and 27 or 5 o~ the JO or on1y 16.7%

of the Trinidad herds can be considered as having acceptable

fertility. When this finding is compared with previous

reports, Boyd et al. (1954) 1.68, Hollon et~. (1967) 1.7J,

Bozworth et al. (1972) 1.8, Morrow !1 al. (1966) 1.84, Van

Demark and Salisbury (1950) 1.97 and Pelissier (1970, 1972)

2.55 and 2·.44 services per conception respecti ve1y, i t wou1d

seem that herds H and l in Quebec and herds J, 6, 14, 19, 21,

22 (20%) and both Government herds do not compare favourab1y.

Again the trend in the Government kept Purebred Holstein

/-~ .. -...."\ f , , ~

Table 5. Mean Production and Reproduction Parameters for Cows (Quebec Herds).

Herd No. No. of Daily Production Ca1ving No. of Services Cows (kg) Interva1 Cows per

(days) Conception

A 9 1 17.9:t 1.0 ,387 :t 12.2 la 1.7 :t 0.,3

B 9 18.2 :t 1.4 415 :t 21.2 1,3 1.8 ± 0.,3 C la 18.0 ± 1.4 4,38 ± 28.4 la 2.,3 ± 0.4 D 8 14.9 ± 1.1 397 ± 16.0 9 2.2 ± 0.4 E 9 17.3 ± 1.7 420 ± 20.1 10 2.0.± 0.4 F 10 16.6 ± 1.2 418 + 19.5 10 1.7 ± 0.3 G 7 15.3 ± 1.2 374 ± 9.1 10 1.9 + 0.4 H 9 15.3 ± 0.8 367 ± 12.9 la 2.7 .:t 0.7 l 6 12.1 ± 1.9 406 + 15.4 10 3.2 + 0.9 -J 6 1,3.4 ± 1.,3 ,385 ± 24.7 10 2.2 + 0.4 K 7 1,3.9 ± 1.6 ,358 ± 6.8 10 1.6 ± 0.2

1Va1ues are means ± S.E. for number of anima1s invo1ved.

.~

" \.n

,~ ,r"'-"

Table 6. Mean Production and Reproduction Parameters for Cows (Trinidad Herds).

Herd No. No. of Dai1y Production Ca1ving No. of Services Cows , (kg) Interva1 Cows per

,da~sl Conce:etion

1 18 10.5 + 0.7 1 426 ± 18.9 21 1.6 + 0.2 2 12 8.1 ± 0.6 444 ± 29.9 13 2.0,± O.)

) Il 7.7 + 0.5 520 ± 55.9 12 2.8 ± 0.3 4 13 9.5 ± 0.4 469 ± 28.1 17 2.2 ± 0.3 5 13 7.6 ± 0.7 436 + 26.8 18 1.4 ± 0.2 6 10 7.4 ± 0.7 464 + 25.9 13 2.6 ± 0.5 7 15 9.5 + 0.4 388 ± 14.8 18 2.0 ± 0.2 8 13 10.1 ± 0.5 405 + 21.6 18 1.9 ± 0.2 9 9 7.8 + 0.5 368 :t 13.8 Il 2.3 ± 0.3

10 17 2.4 ± 0.4 Il 13 8.3 ± 0.6 350 ± 16.6 18 1.9 + 0.2 12 18 1.5 ± 0.2 13 12 2.0 + 0.2 14 13 10.3 + 0.7 465 ±. 34.0 16 2.8 ± 0.7 15 14 2.0 ± 0.2 16 16 2.0 ± 0.2 17 8 6.5 ± 0.5 418 ± 27.3 10 2.0 ± 0.3 18 10 5.8 ± 0.5 483 + 50.4 10 2.3 ± 0.3

-..J 0'\

~

,...~-

Table 6 Cont'd

Herd No. No. of Dai1y Production Ca1ving No. of Services Cows (kg) Interva1 Cows per

~da~s~ Conce12tion

19 7 7.0:t 0.4 516 :t 38.4 7 4.2 ± 1.1 20 13 7.2 + 0.3 433 :t 16.8 15 2.1 ± 0.3 21 7 10.7 :t 0.6 380 ± 27.6 12 2.9 ± 0.7 22 Il 10.1 ± 0.8 420 ± 25.4 17 3.0 ± 0.6 23 11 8.3 ± 0.4 416 ± 18.8 11 2.1 ± 0.2 24 12 10.0 ± 0.5 450 + 35.3 17 2.4 ± 0.4 25 11 10.1 ± 0.7 417 ± 27.1 12 1.7 ± 0.2 26 8 10.0 ± 0.5 456 ± 38.0 16 1.9 ± 0.1 27 Il 9.2 ± 0.7 439 ± 28.7 14 1.8 ± 0.2 28 Il 10.3 ± 0.6 458 ± 37.0 12 2.1 ± 0.5 29 13 9.1 ± 0.3 448 ± 22.0 14 2.2 ± 0.3 30 10 8.2 ± 0.6 506 + 35.6 11 2.3 + 0.2

, ·Va1ues are means ± S.E. for number dr anima1s invo1ved.

--.:l --.:l

J

, .

Table 7. Mean Production and Reproduction Parameters for Cows. (Governrnent Herds Centeno, Trinidad).

, Herd No. No. of Daily Production Calving No. of Cows (kg) Interval Cows

(days)

Purebred 29 9.6 ± 0.4 1 488 + 24.5 47 Holstein

Crossbred 35 7.9 ± 0.4 435 + 16.2 107 HOlstein/ Zebu

IValues are means ± S.E. for nurnber of animaIs involved.

Services per

Conception

3.0 ± 0.2

2.7 ± 0.2

" co

, .. J

79

he rd of 3.0 services per conception resembles that observed

in Jamaica of 3.3 (Zemjanis,1965).

First service conception rates of from 65 to 75% are

commonly quoted by artificial insemination (A.l.)

organizations in the United States (Pelissier,1972). Records

from the A.I. Centre (Trinidad) indicated that the average

first service conception rates for the bulls were 66% in

1969 and 69% up to May 1971. Artificial insemination data

are reported in terms of 60 to 90 day non-return rate.

Although the majority of the conceptions in this study was

based on actual calvings the difference between conception

and non-return rate should be recognized since Graham (1968)

reported that an 18% 60 to 90 day non-return rate was

reported for buffer that contained no sperm, and that a 24%

rate was reported for semen that contained only dead sperme

b. Calving Interval

Calving Interval calculations were based on the period

between ca1vings. This is one measure of breeding efficiency,

a1though it cannot be used alone to describe a herdls

breeding efficiency because it does not account for cows

cu1led after failure to conceive. According to Speicher

and Meadows, (1967) a twelve-month ca1ving interval is

desirable and economica1ly justified by greater return over

feed cost than with longer intervals.

If a twe1ve-month calving interval is idea1, a cow

80

must conceive by 90 days atter calving. Touchberry ~ al.

(1959) ca1culated that with 60% tirst service conception,

a herd would need a service interval of 47 to 60 days to

maintain a 365-day ca1ving interva1. Tables 5. 6 and 7

show that only herds H. K and G (27%) of the Quebee Herds

and only 9 and Il (6.7%) of the Trinidad Herds would

qua1ify in this category. with herds A, D and J (Quebec) and

7 and 21 (Trinidad) being borderline. Speicher and Meadows

(1967) conc1uded that delay in conception beyond 86 and up

to 116 days after freshening reduced milk and calf returns

over feed cost an average of $.50 for each day beyond 86

days. When conception was delayed 117 days or longer,

returns were decreased by $.78 for each day beyond 86 days.

Louca and Legates (1967) reported a more modest loss of

%.50 in milk and calf loss for each excessive day open.

Pe1issier (1972) considered a 108s of $.70 per day in excess

of a year1y calving interval as a reasonab1e adjustment of

the two former reports to current market priees.

When one considers the additional expenses for

replacement cost, additional breeding costs and veterinary

services and Medication it would seem that when the

consequences of low fertility are translated into economic

terms the magnitude of this problem can be tremendous.

Viewed in this light, then 45% of the Quebec herds (calving

interva1 over 400 days) are losing a tidy suro annual1y. The

picture for Trinidad is of a greater significance since 70%

81

of the herds and both Government herds have calving intervals

exceeding 400 days. In fact the very survival of herds 3, 19

and 30 with calving interva1s exceeding SOO days and herd 18

with calving interva1 of 483 days with a high Standard Error

of SO days, seem to be in jeopardy. Several authors have

stressed the importance of proper heat detection. Johnson

(1966) reported that difficulty in detecting heat is a

common cause of long ca1ving intervals. He indicated that

heat detection can be improved by proper training and more

careful observation. Johnson and Ulberg (1967) compared the

reprOduction efficiency of seven herds and found that days

lost per cow-year due to missed heats ranged from 9 to 38

days. Hall ~ Ai. (1959) found that 30% more ~eats were

detected by checking cows 4 times daily instead of twice.

Zemjanis ~~. (1969)proposed that only 10% of aIl anestrus

was due to disorders of the reprOductive tract. The remaining

90% was due to fai1ure to observe estrus, either from

inadequate observation or variations in intensity of estrous

symptoms.

Many dairymen attribute long calving intervals to

silent or short heat periods, and a few even maintain that

sorne cows just do not come in heat. A comparison of

individual herds shows that some dairymen are doing better

than others with heat detection and others might do better

if they tried harder. Such l believe would be the case

particularly with herds 3, 19 and 30 (Trinidad), for these

..' , \.

82

herds support the suspicion that these dairy farmers do not

give heat detection the concentration that is required.

c. Milk Production

Mean daily production for Quebec, Trinidad, and the

Trinidad Government herds are shown in Tables 5, 6 and 7.

With the exception of herd l (Quebec), it would appear that

the higher producing herds have longer calving intervals

than the lower producing ones. However, in the Trinidad

herds there is no particular trend shown. In rnany cases the

lower producing herds have longer calving intervals than

the higher producing ones. In the Government herds, the

hjgher producing Purebred Holstein he rd (9.6 :t 0.4 kg/day)

has a 53 day longer calving interval than the Crossbred

Holstein/Zebu herd (7.9 :t 0.4 kg/day).

The results of this study indicate that lactation

seern to have no effect on services per conception in any of

the herds.

Reports on the effects of lactation on fertility

have been inconsistent. Eckles (1929) and Currie (1956)

found that lactation had no effect on reproduction. However,

Lewis and Horwood (1950), Mc Taggart (1961), Steele et al.

(1967), and Varejcko (1968) have indicated that lactation

is a contributing factor to herd infertility. Lewis and

Horwood (1950) found that average calving interval has been

longer for Holsteins than for other breeds. They suggested

83

that the greater average production level May be responsible

for this difference.

2. Blood Components

The variability of bovine blood cellular components

May be attributed to breed, age, general environment, diet,

production level, and subclinical infections. Factors such

as method and precision of determination, time of day of

collection, and muscular activity have some bearing on the

ultimate values deriv.ed (Wood and Kramer,1968).

Analyses in this study were restricted to serum,

calcium, serum inorganic phosphorous and Hematocrit (Packed

Cell Volume) with the main interest being centered on blood

inorganic phosphorous levels on account of low levels being

widely associated by several authors with a decrease in

conception.

a. Serum Calcium

Serum Calcium values for each herd were well within

the established range with relatively small variations in

Standard Error among the herds in various environments

(Tables 8, 9 and 10). However, values for herds A and C

(Quebec) of 12.4 + 0.2 and 12.5 ± 0.3 mg/100 ml were slightly

above the higher range and these could be attributed to the

higher concentrations of calcium in the feed supplied. This

is borne out by Table Il, where the estimated intake of

calcium per cow per day was 147 and 215 g respectively.

Table 8. Mean Concentration of B100d Components in Cows (Quebec Herds).

Herd No. No. of AnimaIs Serum Serum

Normal A B

C

D

E

F

G

H

l

J

K

Dairy breeds 10 13 10

9 10 10 10 10 10 10 10

(Range)

Calcium Inorganic mg/100 ml Ph ..... os.p horous

mg/100 ml 1 2 9.4 - 12.2 4.0 - 6.0

4 12.4 ± 0.2 Il • .5 + 0.2 12 • .5 ± 0.3 10.4 + 0.2 9.6 ± 0.2

10.0 ± 0.1 10.2 ± 0.2 10.4 ± 0.2 10.6 ± 0.1 10.2 ± 0.2 10.3 + 0.2

4.6 ± 0.3 .5.4 + 0.2 .5.1 + 0.2 .5.2 ± 0.2 .5 • .5 ± 0.4 .5.9 ± 0.2 .5.4 + 0.2 .5.3 + 0.3 4 • .5 ± 0.2 6,2 ± 0.2 .5.2 + 0.2

CalP Ratio

2.8 + 0.2 2.1 + 0.8 2.4 ± 0.9 2.0 ± 0.8 1.8 ± 0.1 1.7 + 0.1 1.9 ± 0.8 2.0 + 0.2 2.3 + 0.9 1.6 + 0.7 1.9 + 0.7

Hematocrit (PCV)

% volume

24 - 463

27.3 ± 0.3 32.9 + 0.9 32.6 + 0.6 33.2 + 0.1 32.2 + 0.9 30.8 + 0.6 32.1 + 0.9 29.8 ± 0.1 32.9 + 0 • .5 2.5.3 :!:. 0.4 32.8 + 0.9

1Benjamin, M. Out1ine of Veterinary C1inica1 Patho1ogy. Iowa State University Press, Ames, Iowa. 1965.

2Nutrient Requirements of Dairy Catt1e, fourth revised edition, 1971 National Academy of Sciences.

3Scha1m, O.W. Veterinary Hemato1ogy. Second Edition 196.5. Lea & Febiger, Phil. 4Va1ues are means ± S.E. for number of animaIs invo1ved.

<Xl -1="

:...1

/....-- ...

1

Table 9. Mean C9ncentration of Blood Components in Cows (Trinidad Herds).

Herd No. No. of AnimaIs Serum Serum CalP Hematocrit Calcium Inorganic Ratio (PCV)

mg/lOO ml Ph~horous % volume m 100 ml

Dairy breeds (Range) 1 2 24 - 463 Normal 9.4 - 12.2 4.0 - 6.0 21 4 6.8 ± 0.2 1.5 + 0.1 )0.1 + 0.7 1 10.6 ± 0.3

2 13 Il.0 :!: 0.4 7.5 + o.) 1.5 ± 0.1 27.2 ± 0.7 3 12 10.3 ± 0.4 6.3 ± 0.2 1.6 ± 0.1 28.6 ± 1.0 4 17 10.6 ± 0.3 6.0 ± 0.0 1.7 ± 0.0 27.9 ± 0.7 5 18 10.6 ± 0.3 7.2 ± 0.2 1.4 ± 0.0 28.4 + 0.6 6 13 Il.J ± 0.3 6.) + 0.2 107 ± 0.0 29.4 + 0.0 7 18 9.9 ± o.) 6.4 ± 0.1 1.5 ± 0.0 )0.8 ± 0.5 8 18 Il.4 ± 0.5 6.7 ± 0.2 1.7 ± 0.0 J2.2 ± 0.6 9 Il 10.0 + 0.5 6.9 ± 0.4 1.5 ± 0.1 30.2 ± 1.0

10 17 Il.0 ± 0.3 7.5 + 0.3 1.5 + 0.0 29.8 ± 0.6 Il 18 Il.9 ± 0.4 6.J ± 0.1 1.0 ± 0.0 32.7 ± 0.6 12 18 Il.0 ± 0.3 6.6 ± 0.2 107 ± 0.0 31.0 ± 0.5 13 12 Il.8 ± 0.0 6.6 ± o.) 1.7 ± 0.0 )1.1 + 0.9 14 16 10.9 ± O.) 7.7 ± 0.2 1.4 ± 0.0 )0.7 ± 0.8 15 14 Il.5 ± 0.5 7.9 ± O.) 1.5 ± 0.1 32.7 ± 0.7 16 16 Il.5 ± 0.4 7.5 ± 0.2 1.5 ± 0.0 31.3 ± 0.8 17 10 10.8 ± 0.4 6.4 ± 0.2 1.7 ± 0.1 28.3 + 1.0 co

\J\

J

Table 9 Cont'd.

Herd No. No. of Anima1s

18 10 19 6 20 15 21 12 22 17 23 9 24 17 25 12 26 16 27 14 28 12 29 14 30 11

Serum Calcium

mg/100 ml

11.0 + 0.4 11.3 ± 0.7 10.9 ± 0.4 10.9 ± 0.4 12.1 ± 0.3 11.2 ± 005 10.7 ± 0.4 11.3 + 0.5 11.7 ± 0.3 11.2 + 0.3 10.8 ± 0.5 10.5 ± 0.4

9.8 + 0.1

Serum Inorganic

Phos'phorous m.gf100 ml 5.9 ± 0.2 5.9 ± 0.4·:~ 5.7 ± 0.2 5.6 ± 0.2 6.8 ± 0.2 5.9 ± 0.1 6.9 ± 0.2 5.9 ± 0.2 5.9 ± 0.3 6.2 + 0.1 5.6 ± 0.2 5.9 + 0.2 6.9 + 0.3

CalP Ratio

1.9 + 0.1 1.9 ± 0.0 1.9 + 0.1 1.9 ± 0.0 1.8 ± 0.0 1.8 ± 0.7 1.3 ± 0.1 1.9 ± 0.1 1.9 ± 0.9 1.8 ± 0.1 1.9 + 0.1 1.8 + 0.1 1.4 ± 0.1

Hematocrit (PCV)

% volume

27.8 + 0.6 25.8 ± 1.1 25.9 ± 0.9 31.6 + 0.6 29.5 + 0.7 29.1 + 0.8 30.9 + 1.0 32.6 ± 0 • .5 31.1 :t 0.7 29.4 + 1.0 31.1 + 0.8 29.7 ± 0.7 30.7 ± 0.7

1Benjamin, M. Out1ine of Veterinary C1inica1 Patho1ogy. Iowa State University Press, Ames, Iowa. 1965.

2Nutrient Requirements of Dairy Catt1e, fourth revised edition, 1971 National Academy of Sciences.

3Schalm, O.W. Veterinary Hemato1ogy. Second Edition 196.5. Lea & Febiger, Phil.

4Values are means + S.E. for number of animals involved.

CP 0\

,-1

....... -., ( ~ ,"'-'

Table 10. Mean Concentration of Blood Components in Cows (Government Herds, Centeno Trinidad).

Herd No. No. of AnimaIs Serum Serum CalP Calcium Inorganic Ratio

mg/lOO ml Ph~horous m 100 ml

Normal Dairy breeds (Range) 9.4 - 12.2 1 4.0 - 6.0 2

Purebred 47 Il.2 ± 0.2 Holstein

4 6.1 + 0.1 1.8 ± 0

Crossbred 107 Il.6 ± 0.2 6.3 ± 0.1 1.8 + 0 Holstein! -Zebu

lBenjamin, M. Outline of Veterinary C1inica1 Pathology. Iowa State University Press, Ames, Iowa. 1965.

2Nutrient Requirements of Dairy Catt1e, fourth revised edition, 1971 National Academyof Sciences.

Hematocrit (PCV)

% volume

24 - 463

30.2 ± 0.5

35.2 ± 0.4

3Schalm, O.W. Veterinary Hemato1ogy. Second Edition 1965. Lea & Febiger, Phil.

4Values are means ± S.E. for number of animaIs involved.

co ~

J

88

Herds E, 9.6 + 0.2 (Quebec) and 7, 9.9 + 0.3 and 30, - -9.8 + 0.1 mg/100 ml (Trinidad) fall closely to the lower

value of the range. Their estimated calcium intakes

(Table Il) of 116, 67 and 8S g per day respectively seem

quite adequate, therefore these low serum calcium values

might be due to a combination of factors since the time of

day of collection from each herd was not standardized.

There is 1ess variation among the Trinidad herds than

among the Quebec herds (Tables 8, 9 and 10) and this could

be due to the wide variation of roughage and grains grown

on Quebec Farms as compared to the almost constant pastures

of pangola grass and mixed concentrate fed to the Trinidad

Herds.

b. Serum Inorganic Phosphorous

Previously published reports indicated that drop in

blood phosphorous leve1 occurred before any outward c1inical

signs of phosphorous deficiency deve10ped (Theiler ~ al., 1927,

Malan et gl., 1928). Palmer and Eckles (1927) reported that

the blood phosphorous level in animaIs on a deficient diet

varied from 1.07 mg/lOO ml to 6.S6 mg/lOO ml, depending on

the degree of phosphorous deficiency. In another deficiency

study, heifers fed bone mea1 had b100d phosphorous·levels of

S.O mg/lOO ml, whereas the 1evel in the control group was

2.3 mg/lOO ml(Ma.1an et al., 1928).

More recently, Snook 1(1964) observed low conception

.89

rates in high producing dairy cows associated with low blood

phosphorous concentrations. Morrow (1969) observed that

heifers with low blood phosphorous levels ).9 mg/100 ml showed

signs of rough coat, chewing on wood, and infertility as

indicated by the need for repeated', .. breedings. When the

blood phosphorous levels were increased to 6.6 mg/100 ~l

fertility improved from 2.8 services per conception to 1.)

services per conception.

Mean blood phosphorous levels are shown in Tables

8, 9 and 10. Again like in the serum calcium values, all

herds from Quebec fall weIl within the established range with

herds A, 4.6 ± O.) mg/100 ml and l, 4.5 ± 0.2 mg/lOO ml

hovering towards the lower range. Although Herd l among the

Quebec herds, exhibited the greatest tendency towards

infertility ().2 ± 0.9 services per conception), its average

of 4.5 ± 0.2 mg/lOO ml coincides with the 4.5 mg/100 ml

considered by Hignett, as reported by Munro (1957), as

adequate for high fertility. Herd Ais fertility i8 relatively

high having 1.7 ±:O.) services per conception and )87 ± 12.2

days calving interval.

The me ans for serum inorganic phosphorous are higher

in practically aIl instances in the Trinidad herds (Tables 9

and 10) than in the Quebec herds (Table 8). This is unusual

when a comparison is made of the estimated p~osphorous intake

on Tables Il, 12 and 1) and from the fact that very little

mineraI supplement is fed in Trinidad, except for blocks of

90

Cobalt-Iodized Salt. In fact sorne of the means are higher

than the higher range and sorne values are closer to those of

yearling heifers 6-8 mg/100 ml (Morrow,1969). However,

these values are lower than those for the Government herds

of 17.2 ± 0.5 mg/lOO ml and 18.2 ± 0.3 mg/100 ml for the

Crossbred Holstein and Purebred Holstein herd found by

Davidson (1970). These values were also comparable with

those of Rusoff ~ âl. (1955) of 4.61 to 7.24 mg/100 for

Jersey and Crossbred heifers, with that of Lane et al. (1968),

mean for Guernsey cows of 6.1 mg/100 ml, and with Steevens

~~. (1971), mean for 27 HOlsteins, 15 Ayrshires and 6

Guernsey cows of 6.3 mg/lOO ml which increased to 7.5 mg/100 ml

when 0.6% phosphorous was fed.

Changes in blood constituents have been suggested as

measures of adaptability. Reports by Blincoe and Brody

(1951) and Rusoff et gl. (1951) indicate that high hemoglobin

values are associated with high adaptability to extreme

conditions of temperature. This was also true for specifie

gravit y, plasma inorganic phosphorous and hematocrit levels.

Blincoe and Brody also reported no obvious changes in blood

composition until 650 F and above when there is a marked

reduction in ascorbic acid and cholesterol levels. These

changes were associated with reduced feed intake. Tables

12 and 13 indicate a lower feed intake in the Trinidad animaIs

than in those in Quebec (Table Il), and since the Purebred

91

Holstein animaIs were initially imported into Trinidad from

Canada, the higher atmospheric temperatures and the lower

feed intake may account for the higher serum inorganic

phosphorous levels.

The mean values of 6.3 ± 0.1 mg/lOO ml for the Crossbred

HOlstein/Zebu cows are also comparable with those of Rusoff

et al. (1955) for Crossbred Jersey cows.

c. CalP Ratio

The CalP ratio was calculated from values of serum

calcium and serum inorganic phosphorous in each herd. Tables

8, 9 and la outline the respective values. Since the widely

recommended ratio is III or 211 or as close as possible to

these ratios only herds A, 2.8 ± 0.2, C, 2.4 ± 0~9 and l,

2.3 + 0.9 to 1 (Quebec, Table 8) can be considered as

falling above the normal. Whether this ratio has any effect

on the low fertility of herds C and l is not clear since herd

A has a high fertility (Table 5) and their ratio do not vary

very widely.

With the exception of herds 22 and 26 with relatively

high Standard Errors, aIl the Trinidad herds along with the

Governrnent herds, are weIl within the recommended ratios

(Tables 9 and 10).

d. Hematocrit (Packed Cell Volume)

In most tropical environrnents blood parasitism and

92

subclinical infections are numerous and impose a tremendous

stress which can increase variability of blood determinations.

Schalm (1965) considered that the differences in red cell

number of cattle as reported from different regions of the

world are of such magnitud~ as to suggest that breed, climate

and level of nutrition May have a significant influence on

red cell number and size in the cow.

In Tables 8, 9 and 10 are set out values for mean

Hematocrit. AlI herds fall within the normal range of

24 -46% volume (Schalm,1965). V~lues, in the main, also

compare with means for Holstein cows of 31.32% PCV reported

by Ferguson (1937). Herds A and J (Quebec) 27.3 ± 0.3% and

25.3 + 0.4% respectively, fall close to the lower range.

The significance of this is not clear but May suggest sorne

form of infection with internaI parasites.

In the Trinidad group (Table 9), herds 2, 3, 4, 5 and

17, 18, 19 and 20 are aIl close to the lower range. Trinidad

is infested with Boophilus ticks and introduced cattle have

suffered an illness characterised by fever, anaemia, jaundice

and sometimes death, occurring about two to six weeks after

the animaIs were put on tick infested pasture. Both bovine

babesiasis and bovine anaplasmosis have been recorded in

Trinidad, and Boophilus ticks are reported vectors of both.

Indeed, both disease May occur simultaneously in the same

animal (Williams and Gonzale~ 1968).

At the time of visit Many of the cows in herds

l . \ ' \. "

93

4, 18, 19 and 20 were covered with a certain amount of ticks.

Further Dr. Clive R. Ali (personal communication) has

isolated Coccidiosis, Haemonchus contortus and Trichostrongylus

axei from Many of these herds so that both external and

internaI parasites May account for the low hematocrit values.

Similar low values of mean 28.65% and range 19.0 - 33.0% were

reported for Holstein-Friesian in Nigeria (Wood and Kramer,

1968). These workers attributed this to the known incidence

of acute trypanosomiasis among sorne of the cattle, possible

effect of other subclinical blood parasitism, and to ehronic

and insidious form of trypanosomiasis which is not easily

recognised clinically, and irrespective of nutrition, tends

to alter the normal blood picture.

The Mean hematocrit value of 35.2 ± 0.4% PCV for the

Government Crossbred Holsteiq/Zebu herd is higher than for

aIl Holstein herds. This value is comparable to those for

N'Dama and Muturu of 36.00% and 36.2% PCV (reported from

Nigeria by Wood and Krame~ 1968); and earlier for Jersey-Red

Sindhi crosses by Rusoff et al. (1955). Blincoe and Brody

(1951) similarly reported higher hematocrit values in Brahman

(Indian evolved) than in Brown Swiss (European evolved)

cattle.

3. Feed Intake

a. Chemical Composition

In Appendix Tables l, 2 and 3 are set out details of

94

chemi.cal composition of aIl feeds examined on the Quebec

Farms. Comparison of these figures with analytical values

for similar feeds set out in Feeds and Feeding (Morrison,1959)

and Nutrient Requirements of Dairy Cattle, National Academy

of Sciences (1971) shows small variations anly. It is thus

presumed that digestibilit~es will also be similar.

For Trinidad, Appendix Table 4 shows the Chemical

composition of the Commercial Dairy Ration mixtures. Rations

l, 2, J and 4 were each prepared by a different Feed Company.

When compared to the Standard Formulation (Table 2) one can

observe the variations, and there are even some variations

among Company's preparation. The high cellulose content of

Ration No. 4 suggest that this Company is not using the

ingredients as specified in the Standard Formulation. In

fact there were visible indications that this ration contained

pea hulls which are known to be very high in cellulose content

(Appendix Table 4). The high cellulose content will no doubt

de crea se the digestibility of the feedstuff.

Since these feed companies are not required by law in

Trinidad to declare, at least maximum and minimum guarantees

of nutrient levels, there is always the possibility that sorne

entrepreneurs are going to take undue advantage of such a

situation. Chemical analyses for citrus pulp and coconut

meal are comparable with values reported by Creek (1967) and

by Devendr,a and Gohl (1970).

Appendix Tables 6 and 7 outline the Chemical Composition

, .... .1

l

95

for pangola and napier grass respective1y. There are no

known recorded tables of composition for Caribbean feedstuffs

so that values are compared with other published data.

Dry Matter values for pango1a grass are variable and

reflect the trend observed by other workers of increasing

dry matter with increasing maturity and decreasing crude

protein content (Butterworth ~ !!., 1961; Vicente-Chandler

~ ~., 1964; Grieve and Osbourr, 1965). The range in NVI

values from 24.1 to 37.4 are comparable to those of Grieve

and Osbourn (1965), Minson and Milford (1966), and Quintyne

(1972), at similar stages of maturity. There is a wide range

of crude protein from 7.6 to 18.8% depending on the stage of

maturity and the level of management. These values are

comparable with, and reflect the same trend of 5 to 8%

increasing to 18-20%, observed in Jamaica by Creek (1967)

and by Many other workers (Butterworth, 1961; Butterworth

et gl., 1961; Vicente-Chandler et ~., 1964; Grieve and

Osbourn, 1965; Gomide ~ gl., 1969; Devendra and Gohl, 1970).

Cellulose content was simi1ar to values reported by Gomide

~ gl. (1969) and Quintyne (1972). The mineraIs, calcium and

phosphorous, although there were slight variations, were

comparable to those of Vicente-Chandler ~ al. (1964) and

Gomide ~ §l. (1969).

Chemical composition for napier grass was comparable

to values reported by Vicente-Chandler ~ gl. (1964); Gomide

et gl. (1969), and Devendra and Gohl (1970). Where the major

(

elements of nutrition are adequate for health and production,

it is cornrnonly accepted that the amounts are sufficient to

maintain normal reproductive processes of early pregnancy.

b. Energy

In young animaIs, an insufficient supply of energy

results in retarded growth and delay in the onset of puberty;

in mature dairy cattle, it results in decline in milk yield

and loss of body weight while a prolonged and severe energy

deficiency May depress reproduction.

Tables Il, 12 and 13 outline the estimated daily net

energy intake whereas Tables 14, 15 and 16 show requirements.

(based on Nutrient Re~uirements of Dairy Cattle 1971,

Appendix Table 8) and the differences in intake for the Quebec,

the Trinidad herds and the Government herds respectively.

With the exception of herds C and G (Quebec), aIl herds are

receiving less than their requirements, whereas Herd l is

receiving just slightly above one-half (Table 14). Whether

the apparent herd infertility in Herd l can be ascribed to

insufficiency in ration is not clear since Herds A, F and K

of high fertility are also in negative energy balance. Herd

l May not always be in low energy intake since intakes were

based on winter feeding and not on the summer pasture periode

Generally the high producing dairy cow in the first

month or two of lactation is a special case of undernutrition

as she is usually in negative energy balance even when

(r "'

Table Il.

Herd No. No.

A 9 B 9 C 10 D 8 E 9 F 10 G 7 H 9 l 6 J 6 K 7

, "

Mean Body Weight, Dai1y Production and Estimated Dai1y Feed Intake. (Quebec Herds).

Body Dai1y EstimatedP-eed Intake Weight Production ENE Protein Ca P CalP

(kg) (kg) (Meal) (kg) (g) (g) Ratio

560.9 17.9 17.9 2.8 147 97 1·5 602.7 18.2 19.9 2.9 118 101 1.1 620.5 18.0 26.3 3.2 215 91 2.4 503.6 14.9 16.3 2.3 125 56 2·3 577.3 17.3 18.4 2.7 116 49 2.4 560.9 16.6 16.7 2.2 93 75 1.3 550.5 15.3 20.4 2.5 192 53 3.7 493.6 15.3 15.9 2.1 102 74 1.4 525.9 12.1 9.7 1.4 87 50 1.8 528.6 13.4 16.9 2.1 86 63 1.4 558.6 13.9 16.9 2.1 69 93 0.8

Il''-~

\0 '1

..J

Table 12. Mèan Body Weight. Dai1y Production and Estimated Dai1y Feed Intake. (Trinidad Herds).

Body Dai1y Estimated Fee~d~lntaKe Herd No. Weight Production ENE Protein Ca P Ca,P No,; (kg) (kg) (Meal) (kg) (g) (g) Ratio

1 18 450.9 10.5 10.5 1.9 91 56 1.6 2 12 444.5 8.1 10.8 2.5 68 67 1.0 3 Il 430.9 7.7 10-7 2.0 83 45 1.8 4 13 457.3 9.5 Il.2 2.1 78 43 109 5 13 436.4 7.6 9.7 2.2 62 55 1.1 6 10 460.0 7.4 9.4 1.6 48 43 1.1 7 15 442.3 9.5 9-7 1.6 67 63 1.1 8 13 478.6 10.1 Il.5 2.3 60 68 0.9 9 9 447.3 7.8 9.6 1.3 53 49 1.1

10 17 486.4 8.2 1.0 41 29 1.4 Il 13 510.5 8.3 10.0 1.3 55 54 1.0 12 18 489.1 8.9 1.2 43 38 1.1 13 12 431.8 8.5 1.6 38 31 1.2 14 13 487.3 10.3 10.5 1.4 75 38 2.1 15 14 514.1 10.5 1.3 21 21 1.0 16 16 467.3 8.4 1.6 21 21 1.0

\0 OJ

., -.. ~

Table 12 Cont'd.

Body Dai1y Herd No. Weight Production ENE No. {kgl {kgl {lVIca1l

17 8 458.6 6.5 8.6 18 10 436.8 5.8 9.9 19 7 454.1 7.0 10.1 20 13 433.6 7.2 8.3 21 7 46.5 • .5 10.7 10.8 22 Il 47.5.5 10.1 11.1 23 11 465.0 8.3 10.9 24 12 526.8 10.0 Il.6 25 11 490.0 10.1 10.2 26 8 515.5 10.0 10.6 27 Il 448.6 9.2 9·3 28 Il 527.; 10.; 12.7 29 1; 4;9.1 9.1 9.6 30 10 462.7 8.2 10.9

Estimated Feed Intake I:'rotein Ca P

'kgl (g) Cf;)

1.2 76 33 1.8 67 31 1.9 70 43 1.2 64 34 1.7 71 .54 1.7 88 .56 2.4 68 63 2.1 .59 73 1.9 75 59 2.4 74 60 107 71 51 2.; 67 60 1.6 .56 .50 1.6 8.5 27

~-Ca:IP

Ratio

2.5 2.2 1.6 1.9 1.3 1.6 1.1 0.8 1.3 1.2 1.4 1.1 1.1 3.2

l'''''''''

'" '"

..J

Table 131 Mean Body Weight, Daily Production and Estimated Daily Feed Intake. (Government Herds, Centeno, Trinidad).

Body Daily .. -- U __ -EsTimàt-ed Feed Intake

r

Herd No. No. of Weight Production ENE Protein Ca PCalP Obs • (kg) (kg) (Meal) (kgL----.Jg) Cg) Ratio

P/bred Hol­stein Cows

P/bred Hol­stein Heifers

C/bred Hol­stein/Zebu Cows

C/bred Hol­stein/Zebu Heifers

29

16

35

67

603.9 9.6 14.7

466.8 9.4

489.5 7.9 10.6

431.8 8.1

3.1 110 85 1.3

2.0 45 33 1.4

1.9 63 54 1.2

1.3 27 23 1.3

1-' o o

.. -1

r

Table 14. Summary of Requirements and Differences in Feed Intake. (Quebec Herds).

Differences in Feea-lritake R:eguirements Herd· ENE Prote in Ca P ENE Prote in Ca P No. (Meal) (kg) (g) (g) (Mca1) (kg) (g) (g)

A 22.1 2.0 68 50 -4.2 +0.8 +79 +47 B 22.9 2.1 69 54 -3.0 +0.8 +49 +47 C 22.9 2.1 69 51 +3.4 +1.1 +146 +40 D 19.3 1.7 59 43 -3.0 +0.6 +66 +13 E 21.8 2.0 67 50 -3.4 +0.7 +49 -01 F 21.2 1.9 64 48 -4.5 +0.3 +26 +27 G 20.2 1.8 61 45 +0.2 +0-7 +131 +08 H 19.6 1.8 60 44 -3.7 +0.3 +42 +30 l 17.7 1.6 53 39 -8.0 -0.2 +34 +11 J 18.6 1.7 56 42 -1.7 +0.4 +30 +21 K 19.3 1.7 57 42 -2.4 +0.4 +12 +51

1-' o 1-'

1

Table 15. Summary of Requirements and Differences in Feed Intake. (Trinidad Herds).

Reguirements Differences in-Feed Intake Herd ENE Protein Ca P ENE Prote in Ca lio. (Mga1 ) (kg) (g) (g) 'Meal) 'kgl (gl 1 15.6 1.4 45 34 -5.1 +0.5 +46 2 13.9 1.2 39 29 -3.1 +1.3 +29 3 13.3 1.1 38 29 -2.6 +0.9 +45 4 14.9 1.3 43 32 -3.7 +0.8 +35 5 13.5 1.2 38 28 -3.8 +1.0 +24 6 13.4 1.2 37 28 -4.0 +0.6 +11 7 14.9 1.3 43 36 -5.2 +0.3 +24 8 16.0 1.5 46 34 -4.5 ±0.8 +14 9 13.7 1.2 38 29 -4.1 +0.1 +15

10 8.8 0.6 21 15 -0.6 +0.4 +20 Il 14.7 1.3 42 31 -4.7 0.0 +13 12 8.8 0.6 21 15 +0.1 +0.6 +22 13 8.3 0.6 18 14 +0.2 +1.0 +20 14 16.1 1.4 47 35 -5.6 0.0 +28 15 9.2 0-7 21 16 +1.3 +0.6 00 16 8.6 0.6 21 15 -0.2 +1.0 00

P 'gl +22 +38 +16 +11 +27 +15 +27 +34 +20 +14 +23 +17 +17 + 3 + 5 + 6 1-'

0 1\)

.J

~~-,

1 .

Table 15 Cont'd

Reguirements Herd ENE Protein Ca P No. (Meal) (kg) (g) (g)

17 12.8 1.1 )5 26 18 12-7 1.0 )) 25 19 1).1 1.1 )6 27 20 1).) 1.1 )7 28 21 15.7 1.) 46 )4 22 15.6 1.4 44 )) 2) 14.0 1.2 40 )0 24 16.2 1.4 46 )4 25 16.0 1.4 46 )4 26 16.1 1.4 46 34 27 15.2 1.) 42 )1 28 16.4 1.4 47 )5 29 14.6 1.2 42 )1 )0 14.0 1.2 )9 )0

"- ~

Differences in Feed Intake ENE Protein Ca

.. (M~.a.1.) ____ (k~l _lgL_

-4.2 +0.1 +41 -2.8 +0.8 +)4 -).0 +0.8 +)4 -5.0 +0.1 +27 -4.9 +0.4 +25 -4.5 +0.) +44 -).1 +1.2 +28 -4.6 +0.7 +1) -5.8 +0.5 +29 -5.5 +1.0 +28 -5.9 +0.4 +29 -).7 +0.9 +20 -5.0 +0.4 +14 -3.1 +0.4 +46

P (~d

+ 7 + 6 +16 + 6 +20 +2) +)) +)9 +25 +26 +20 +25 +19

- 3

/-

J-I o \..ù

~,

t

Table 16. Summary of Requirements and Differences in Feed Intake (Government Herds). Trinidad.

Reguirements Differences in Feed Intake Herd ENE Protein Ca P ENE Protein Ca P No. (Meal) (kg) (g) Cg) (Meal) (kg) (g) (g)

P/bred 16.9 1.5 47 45 -2.2 +1.6 +6; +40 Holstein Cows

P/bred 8.5 0.6 18 14 +0.9 +1.4 +27 +19 Holstein Heifers

C/bred 14.5 1.3 41 30 -3.9 +0.6 +22 +24 Holstein! Zebu Cows

C/bred 8.0 0.6 18 14 +0.1 +0.7 + 9 + 9 HOlstein/ Zebu Heifers

j-J

~

",

J

105

offered liberal amounts of an adequate diet.

The Committee Report on Pre-natal and Post-natal

mortality in cattle (1968) considered that lack of sufficient

energy is one of the most common forms of nutritional

infertility. Fuquay et!l. (1966) found that level of grain

feeding during the first half of lactation did not signifi­

cantly alter days to first estrus, days open, or total

services for conception. Also, Lamb ~!!. (1965) observed

no difference in reproductive performance of dairy cows fed

alfalfa hay plus grain and those fed alfalfa hay only during

lactation.

However, Mc Clure (1961, 1965, 1970), Mc Taggart

(1961) and Mc Clure and Dowell (1969) observed infertility

syndromes in pasture-fed dairy cows'characterised by low

first service pregnancy rates. These were associated with

a loss of 10% live weight between parturition and mati~,

and low blood-glucose levels in the infertile cows at mating.

This syndrome occurred in herds grazing short, rapidly

growing pasture and has been ascribed to an energy deficiency

in the diet leading to hypoglycemia.

With the exception of herds 12, 13 and 15 and both

heifer groups in the Government herds, aIl the other herds

in the Government and Trinidad groups are in negative energy

balance (Tables 15 and 16). The effect of this energy

deficiency on the fertility of the animaIs is not clearcut

since herds of good fertility (Table 6) are also deficient

c···

(

106

in energy. However, herds 14, 19, 20, 24, 26, 28 and 29

of low fertility are in large energy deficit.

It is questionable whether animal requirements in

the temperate regions are applicable to animaIs in the

tropical regions. Considerable experimental evidence

available regarding the effect of the climaticenvironment

on feed intake of cattle, suggests that high ambient tempera­

tures depress the feed intake of aIl types of cattle, but

that feed intake of ~ taurus is depressed at lower ambient

temperatures than is that of Bos indicus breed (Worstell and

Brody, 1953; Johnson et al.,1958; Johnson et al.,1960;

Johnston et al.,196la, b; Allen, Pan and Hayman,1963;

Randel and Rusoff, 1963).

The effect of high environmental temperatures on feed

intake is very pronounced. Ragsdale et al. (1948) showed

that the feed intake of Holstein and Jersey cattle virtually

stopped when temperature rose to 40.6°C (105°F), and Robinson

and Klemm (1953) stated that rumination in Illawarra Shorthorn

cows ceased at body temperatures above 40°C (104°F). Payne

and Hancock (1957) found, that feed intake among identical

twins divided between New Zealand (mean temperature

12.3°0 (54.2 0 F) and Fiji Mean temperature 24.4°C (76.00F), was

lower in the Fiji twins, the major difference being in hay

intake.

High humidity combined with high environmental

temperatures also seem to have a more depressing effect on

(

107

feed intake than when the humidity is low. Ragsdale ~ g!.

(1953) reported that increasing humidity at environmental

temperatures above 23.90 0 (750 F) depressed the feed intake

of HOlstein, Jersey, Brown Swiss and Brahman cattle, while

Johnson ~!l. (1963) have shown that lactating Holsteins

were managed at environmental temperature of 32.20 0 (900 F),

feed intake was normal when relative humidity was 20 per cent,

but when it rose to 40 per cent there was severe depression

in both dry matter and Total Digestible Nutrient intake.

Since the Mean temperature of Trinidad is relatively

high (Table 1) and humidity is always high, it would be

consistent to find Holstein animaIs in particular to show

reduced feed intake as compared to animaIs in a temperate

zone environment.

The actual energy status of the animaIs in the

Trinidad Herds is not quite clear since the calculations

have0been based on requirements for temperate-zone cattle.

There is a serious gap in the world literature on the nutrient

requirements of animaIs in tropical regions and one must

assume there is a real need for developing research groups

tà attack this problem.

If climate can affect the level of nutrient intake,

body temperature, and the general metabolic function of the

ruminant, it May also affect the efficiency of feed

utilization. The limited experimental evidence of the

overall effect of climatic environment on efficiency of

( !

108

feed utilization under controlled conditions suggest that

increasing ambient temperature decreases efficiency, though

under field conditions the difference may be insignificant

(Hancock and Payne, 1955, Payne and Hancock, 1957; Wayman

et al., 1962) 1>

Since herds 12, 13 and 15 (Trinidad) and the heifers

on the Government Station were meeting their estimated daily

intake from forage alone, this indicates that weIl managed

pangola grass can supplU adequate energy to at least meet

maintenance requirements of dairy animaIs.

Figures 2 and 3 show the variation in NVI (ENE) of

pangola and napier grass at different stages of maturity.

Since Nutritive Value Indices are based on voluntary intake

criteria, the data indicates that intake of pangola grass

May not be affected by stage of maturity although there is

a fairly good indication that napier grass intake is related

to maturity.

Many workàrs have indicated that there are many varied

and limiting factors particularly in the rainy season, which

prevent the actual intake of enough forage, although the

forage may be nutritionally adequate. Rose ~ âl. (1963)

found that when the dry matter content was as low as 11%

animals could not consume enough to meet maintenance

requirements. Morrison (1959) estimated that the normal

amount of pasture consumed by cows is 90 - 150 lbs

(40.9 - 68.2 kg). In order that Herds 2 and 30 with body

(\ " J

....... H

~

Figure 2. Re1ationship between ENE (NVI) and age of pango1a grasse

50

40

• • • - , .-• -• • 1 - 30 • • -• • Il:l -Z Il:l •

20

10

0 2 4 6 8 10 12

Stage of Maturity (Weeks)

109

'-

{

\.

Figure). Re1ationship between ENE (NVI) and age of Napier grasse

60

• 50

• 40

..- • H

~ • - • • )0

• I%l Z I%l

20

10

2 4 6 8 10 12

Stage of Maturi ty (Weeks)

110

.,.

(

III

weights of 444.5 kg and 462.7 kg respectivel~ shou1d meet

maintenance requirements they had to consume 89.1 kg and

92.7 kg respective1y of a 12% Dry Matter forage (Appendix

Table 6). So that gut fill May be a limiting factor to

intake of adequate energy for these herds.

Butterworth ~~. (1961), Mahadevan and Searle

(1968), and Davidson (1969) found that milk production in

the Caribbean increased in the dry season due to increased

dry matter of the forage, and Davidson attributed this to

the fact that grazing is usually stopped during heavy rain­

falls so that energy intake is curtailed •.

Another factor that May depress intake is the increase

of parasitism during the rainy season. The presence of

large numbers of gastro-intestinal parasites affects nutrition

by depressing appetite and decreasing the digestibi1ity of

certain nutrients (Gibson, 1963).

c. Protein

A 1ack of dietary protein will depress the rate of

growth, maturation, and milk production in dairy cattle.

Gestation May be interrupted if the deficiency is severe.

In Quebec (Table 14) with the exception of Herd l,

aIl herds were receiving more than an adequate supply of

proteine The low protein intake of Herd l reflects the low

amounts of forage and concentrate offered by this farmer.

Whether the low energy and protein fed to this he rd contri-

l

\. butes to its higher infertility in aIl the Quebec herds

studied would need further investigation.

112

AlI the herds· under the Trinidad grouping (Tables 14

and 15) were receiving more than an adequate protein supply,

with herds Il and 14 just meeting requirements.

The crude protein content of grasses has long been

held to be a limiting factor in cattle production in tropical

areas. During the rainy season the crude protein content of

weIl managed pangola grass is relatively high, and is adequate

to meet maintenance requirements (Grieve and OSbourn, 1965)

and for maintenance plus a production of 3 gallons of milk

without supplementation (Butterworth ~ al.,196l). The

crude protein content of the pangola grass (Appendix Table 6)

was comparable to that reported by Butterworth et al. (1961)

and by Creek (1967).

It has been genera1ly assumed by some that intake of

dry matter is dependent upon the protein content of the

forage consumed. When the protein content declines, intake

will thus be reduced. Pasture feeding of dairy cattle

invo1ve conditions that MOst commonly produce nutrient

deficiencies of protein and energy. In Many parts of the

world these conditions are frequently aggravated by high

temperatures and deficiency of rainfa1l.

Many workers have reported that the crude protein

content of pangola grass decreases with maturity (Vicente­

Chandler et a1.,1961; Chicco, 1962; Grieve and Osbourn, 1965;

113

Quintyne, 1972) and that in the dry season the protein

content is quite low so that supplementation is necessary

(Butterworth et al., 1961; Creek,1967; Devendra and

Gohl. 1970).

Generally the prote in intake in this study, with one

exception, was quite adequate. Reports of protein intake

affecting fertility involved cases of inadequate intake, and

these were mainly with beef animals (Howes et al., 1963.

Bedrak et al., 1964; Warnick et al., 1965). Sorenson et al.

(1959) reported that in dairy females there was little

evidence that ovarian function was adversely affected by

either under or over-feeding once puberty was reached.

However, Girou and Brochart (1970) observed a trend

of decreasing fertility in dairy cows when the protein supply

was excessive. These workers found that the threshold of

excess of digestible nitrogenous matters compatible with

normal fertilitywas situated between 200 and 300 gm per day.

d. Calcium

A great deal of work has been done on the establish­

ment of the mineral requirement of cattle for maintenance of

health and production, and in many instances on the possible

requirements for reproduction. This is of paramount importance

since in many dairying countries most herds are fed directly

off the farm, and any mineral deficiency in the soil or

pastures may be reflected in the cows. The relation of soils

and forages to welfare of animals dependent on them has been

~-.

, 1

)

114

recognized since the days of Hogg, the Ettrick Shepherd

(1831) in the Cheviot Hills of Scotland, nearly a century

and a half ago.

Tables Il and 14 indicate that aIl the Quebec herds

were receiving more than·their requirements, wi~h Herds

A. C. D and G receiving more than twice their requirement.

This was consistent with Many reports that forages in

general, and legumes in particular, are comparatively high

in calcium. The latter farms were aIl feeding legume hays.

Within the Trinidad herds (Tables 12, 13, 15 and 16)

w.i th "the exception of herds 15 and 16 which were just

meeting their requirements. aIl other herds wereadequately

supplied, and some ev en receiving as much as twice their

requirements. The lower intakes by herds 15 and 16 are

a reflection of the forage since these animaIs are not yet

in production hence they receive very little concentrate.

However, during the dry season the intakes will be increased

when supplementation of citrus Meal, which is high in calcium,

is provided.

The lower intakes of calcium as compared to the

Quebec herds May be due exclusive1y to the fact that no

1egume forage is fed in Trinidad.

Calcium is the mineraI found in largest amounts in

the animal body and is in greatest demand during the growth

period. Authors have quoted varying feed contents as being

desirab1e and satisfactory. Theiler and Green (1932) found

115

that 0.42% of calcium in the diet was satisfactory; Fitch

~ al. (1932) found that the minimum requirement for

reproduction in dairy cattle was 0.18% of the total ration

on a dry matter basis. However, Converse (1954) found

that diets as low as 0.16% were capable of maintaining

health and functions of lactating animaIs. Meigs ~ ~.

(1935) suggested that 25 gm daily for Jersey cows producing

3,000 kg milk in a lactation might be inadequate.

Other reports have indicated that higher amounts of

calcium have increased reproductive performance. Rusoff

"(1950) found that administration of calcium in the form of

oyster shell flour reduced services per conception in dairy

cows from 3 to 6 to 1 to 2 and" animaIs experienced normal

births whereas in 1947 abortion rate was 50%,and 66% in 1948,

although the blood picture for calcium, plasma inorganic

phosphorous and hemoglobin was normal. Ward II al. (1971)

found that feeding dairy cows 200 gm of calcium versus

100 gm but maintaining approximately a 2 to 1 ratio, animaIs

on the former diet completed uterine involution eight days

sooner and that first ovulation occurred six days ear1ier.

Generally it hasbeen found that many cows, especially

those fed on legume forage, consume considerably mare calcium

than is necessary without harmful effects. However,

parturient paresis may result when calcium intake in milking

cows is low.

In this study aIl herds were meeting their calcium

116

requirements based on the Nutrient Requirements of Dairy

Cattle (1971) so it appears that there is no possibility

of lack of calcium in the diets.

e • Phosphorous

The phosphorous intakes and balances after require­

ments are met, for aIl herds are outlined in Tables Il, 12,

lJ, 14, 15, and 16. In the Quebec herds (Table 14) cows in

Herd E are receiving 1 gm below their requirements, whereas

the other herds are aIl adequatley supplied, with herds

A, B, C and K considered as receiving liberal amounts. The

low intake by herd E is due to the low supply of phosphorous

in the silage supplied (Appendix Table 2). The situation

in this herd may be aggravated since this farmer usually

fortify his ration with a 17% calcium and J% phosphorous

mineraI mixture, eXhibiting a 6.1 calciumlphosphorous ratio.

Within the Trinidad and Government herds (Tables

15 and 16), and with the exception of herd No. JO, aIl

animaIs were qui te adequately,' supplied. The deficiency of

J gm per head in herd JO can be attributed to the fact that

this farmer feeds a mixture of citrus meal and pea hulls

which are quite low in both protein and phosphorous and high

in calcium (Appendix Table 4).

Phosphorous requirements for cattle have been studied

for many years and the data linking phosphorous with

infertility have been conflicting and somewhat confused.

( , ,

117

Theiler and Green (1932) associated phosphorous

deficiency with infertilitYJ and abnormalities in repro­

ductive behaviour were reported by Eckles ~~. (1932,

1935) as due to phosphorous deficiency. Estrous abnormalities,

ovulatory abnormalities and difficult calvings were reported

by Palmer ~~. (1941), aphosphorosis was linked with

infertility by O'Moore (1950), and with infertility without

clinical symptoms by Hignett and Hignett (1951). Hignett

and Hignett (1952) suggested that for satisfactory fertility

heifers should receive a daily intake of about 50 gm of

phosphorous.

In contrast to Hignett's and Hignett's findings,

Littlejohn and Lewis (1960), obtained no difference in

fertility between animaIs given 2.0 and Il.4 gm P/lOO kg

body weight daily. Salisbury and Van Demark (1961) considered

limited phosphorous intake to probably be the most prevalent

mineraI deficiency affecting reproduction.

Snook (1964) reported a daily supplement of 20 gm

phosphorous produced a graduaI response in terms of increased

butterfat production and reduced calving interval over a

number of lactations. HOwever, his data do not permit an

evaluation of possible differences in feed intake following

supplementation.

Underwood (1966) has suggested that adverse effects

on estrus and conception are those of a specifie phosphorous

deficiency. More recently, Morrow (1969) reported a response

{ , ..

(

118

to phosphorous supplementation by heifers, whereby increasing

the blood phosphorous from 3.9 to 6.6 mg/lOO ml, reduced

services perconception from 2.8 to 1.3.

Since the successful completion of Many important

metabolic reactions depends on phosphorylation, the initial

and basic effect of phosphorous deficiency is a depression

of feed intake. Little (1970) reported that responses to

phosphorous supplementation in the field are invariably

confounded by, and indistinguishable from those due to

concomitant increases in intake. He further demonstrated a

linear response in the volun~ry intake of phosphorous­

deficient cattle when these were given graded supplements of

phosphorous to a diet adequate in other respects. He also

observed that supplements of phosphorous to such animaIs do

not result in growth responses when increases in feed intake

are not permitted.

The results reported in this study indicate that

apart from herd E (Quebec) and herd 30 (Trinidad)j' aIl herds

would be receiving adequate allowances of phosphorous

according to suggested requirements in Nutrient Requirements

of Dairy Cattle (1971). The significance of the effect of

the low intakes of phosphorous on the infertility of these

herds (herd E, 420 + 20.1 days calving interval, and

2.0 ± 0.4 services per conception; and he rd 30, 506 ± 35.6

days calving interval, and 2.3 + 0.2 services per conception)

cannot be ascertained~ Further investigations would be

119

necessary into this aspect, particularly, in the severe

case as represented by herd JO.

f. CalciumlPhosphorous Ratio

Calcium and phosphorous metabolism are usually

considered together, because of their association in the

skeleton, which contains 99% of the total calcium in the

body, but only 80% of the total phosphorous (ARC 1965).

Hence it is believed that the utilization of phosphorous is

impaired when the ratio of calcium to phosphorous in the diet

varies widely from the commonly accepted optimum of 1-211.

The results of the calcium to phosphorous ratio

intakes for aIl herds are outlined in Tables Il, 12, and lJ.

Herds C, D, E and Gare above the ratio of 2.1 whereas herd

K is below 111. The higher phosphorous to calcium in herd K

is as a result of feeding a mixture of oats and barley which

were high in phosphorous (Appendix Table 1).

In the Trinidad herds, wi th the e:xception of herds

17 and JO, above 2.1 ratio, and herds 8 and 24 below 111, -

aIl other herds are very close to, or weIl within the

optimum ratio. The higher phosphorous content in the forage

of herds 8 and 24 (Appendix Table 6) can be due to a higher

concentration of phosphorous in the soil of these farms.

Herd 30 is fed high amounts of citrus pulp which is low in

phosphorous and high in calcium, which accounts for the high

calcium to phosphorous ratio of 3.2.1.

',,- ...

120

Great interest in the relationship between the

calciumlphosphorous ratio in the diet and fertility has

been shown for Many years. Reports in Many instances have

been inconsistent. Further importance has been attached

to vitamin D status of the animals since vitamin D assists

phosphorous absorption and utilisation.

Hignett and Hignett (1951) found that a high calcium

to phosphorous ratio depressed fertility of heifers when

phosphorous intake was low, but increased it when phosphorous

intake was high; but these effects were minimised when a

high vitamin D status was maintained (Hignett and Hignett,

1953).

O'Moore (1952) reported more severe signs of

aphosphorosis on farms where the pasture exhibited a high

calcium to phospho'i;Jous ratio, al though he recognised that

low vitamin D states could play a contributory role.

Support for this observation was made by Abrams .(1952) who

concluded that the evidence for hypovitaminosis D on growth

and reproduction was sound.

However, Littlejohn and Lewis (1960) found that ratios

between 0.8 and 12.1 and adequate vitamin D had no effect on

fertility. Growth rate was slightly depressed at the high

ratio when the intake was approximately 2.0 gm/100 kg.

More recently, Ward et al. (l971) observed that estrus

occurred earlier after parturition in cows which received

supplemental vitamin D with a calcium to phosphorous ratio

,.

121

of 2.1 than those not receiving vitamin D; and the interval

between parturition and subsequent conception averaged J7

days shorter for cows supplemented with vitamin D than for

those not receiving it.

Steevens ~ âl. (1971) found no significant difference

in reproductive performance between groups fed a Ga.p ratio

or J.l with 0.4 and 0.6% phosphorous respectively, and Ca.P

ratio of 1.5.1 with 0.6% phosphorousr but in the group with

the 0.4% phosphorous, the incidence of ovarian dysfunctions

was higher, and in addition, a larger number of services per

conception was required in the second breeding season.

The results from this study indicate that the majority

of the herds are weIl within the optimum ratio of 1-2.1.

Since the reports of the effects of varying calcium to

phosphorous ratios on fertility, have been so inconsistent,

the significance of herds with ratios outside of the accepted

optimum is not apparent.

Cows in the Quebec herd usually receive sun cured hays,

and during the Summer are exposed to enough sunlight, so that

there is no apparent danger of vitamin D deficiency. Under

Trinidad conditions it seems most unlikely that a deficiency

of vitamin D will ever be a problem of grazingcattle.

122

4. Simple correlations between services per conception and ca1ving interva1s with other parameters.

a. Age

The correlations between services per conception and

calving intervals and various parameters for each herd are

compared in Tables 17 and 18 for the Quebec and Trinidad

herds respectively.

With the exception of herds 18, 19 and 21 (Table 18)

there is no significant correlation between age and services

per conception and ca1ving intervals. The highly positive

significant corrêlation between services per·conception and

age in herds 19 and 21 indicates that as the animals get

older they require more services to conceive. This would be

in agreement with Davidson (1969) who found that within the

Crossbred Holstein herd at Centeno, over a period of 10

years, cows required2.5 services per conception whereas the

heifers required 1.9.

b. Body Weight

HerdsB (Table 17) 9 and 14 (Table 18) show significant

positive correlation between body weight and calving interval.

This would indicate that as body weight increases in these

herds calving interval increases. Herds 9, 10 and 14 show a

significant positive correlation between body weight and

services per conception so that an increase in body weight in

these animals would entail more services to conceive. However,

~-."

Table 17. Simple Correlations of Services per Conception and Calving Intervals with other Parameters (Quebec Herds).

Herd No. A HerdNo-. B ,- "-'Herd -No. C Variables Services Calving Services Calving Services Calving Compared per Interval per Interval per Interval

Conce:g:tion Conce:gtion Conce:gtion

Age -.41 -.;; .54 .45 -.14 -.25 Body Weight -.58 .05 .01 * .72 -.;1 -.19 Milk Prod. -.19 -.01 .;1 -.56 -.07 -.06 Lactation No. -.58 -.1; .59 .;4 -.20 -.26

tfl op s:: Q)

-.01 .05 s:: Ca 0

.2; .1; .28 -.26 El P .;9 -.22 -.09 -.24 .01 -.2; 0 CalP -.26 .23 :15 .24 .25 .IS 0

'CI Hematocrit .24 -.04 -.62 ** 0 .13 -.87 .;2 0 r-f !Xl

Q)

~ Crude Protein -.42 -.05 .;7 -.15 -.22 -.19 op s:: Ca -.37 .15 .17 .25 -.32 -.25 H

'CI P -.42 -.10 .27 -.46 -.19 -.04 Q)

.45 -.06 * .26 Q) CalP -.0; .70 -.09 lit

of! ENE -.47 .01 .27 .44 -.27 -.le J-I 1\)

rD P!I!

\...>

...J

',--"

............. , . \

Table 17 Cont'd

Hard No. D ------ -- n - --Hard -N~ -E-- Herd No. F Services Calving Services Calving Services Calving Variables

Compared per Interval per Interva1 per Interval ConceDti~~ _____ Conception Qo_ncention

Ul

~

Age Body Weight Milk Prod. Lactation No.

~ Ca o a P o o CalP 'g Hematocri t o

.-1 I:Q

Q)

'@ Crude Protein op s:: Ca H

'd P Q) :! CalP of! ENE Ul lïI

-.07 .23 .40

-.11

-.68* .09

-.32 .13

.46

.21

.43 -.49 ~43

-.07 .16

-.12 -.12

-.08 .14

-.17 -.32

.04

.02

.04

.05

.03

.49

.24

.63 *

.31

.. Il -.04 -.05

.24

.60

.69 *

.57 -.23

.59

.46

.16

.43

.22

-.12

.22

-.23 .07

.34

.50

.40 -.19

.41

.36 -.45

.63*

.34

.10

.24

-.17 -.18

.39

.53

.49 -.26

.02

-.37 -.51 -.45 -.49

.05

.03

.06

.45

-.57 -.45 -.39

.24

-.67 * 1-' N -t="

1

r·-·

Table 17 Cont'd

Herd No. G Herd No. H Herd No. l Variables Services Calving Services Calving Services Calvlng Compared per Interval per Interval per Interval

Conception ConceI!tion Conception

Age -.)7 -.0) -.47 -.29 -.l.3 -.)8 Body Weight -.25 -.)7 -.56 .20 .21 -.1) Milk Prod. -.60 -.24 -.18 .58 .9 6** .04 Lactation No. -.)6 -.22 -.5) -.21 .09 .04

(Il ~ ~ Q) * '* * ~ Ca .75 .)6 -.74 -.75 -.18 .)6 0

.78** aP .65 .0) .51 -.49 -.07 0 ** 0 CalP -.)1 -.22 -.77 -.58 .55 .1) '0 Hematocrit .)1 .47 -.44 -.58 -.)6 -.27 0 0

r+f ~

Q)

.!lcI Crude Protein -.55 -.41 -.)6 ~47 .88** .08 «1

~ ** ~ Ca -.47 -.)8 -.28 .55 .92 .02 H * .56 ** '0 P -.70 -.29 -.20 .9) .02

Q) * Q) CalP .82 .09 -.)7 -.08 -.4) .11 Ji:!

of.! .-.42 -.45 .4) * (Il

ENE -.)9 .82 -.04 r:q 1-'

!\)

\..n.

• ..1

1

\

Table 17 Cont'd.

Herd No. J Herd No. K Variables Services Calving Services Calving Compared per Interval per Interval

Conception Conception

Age .40 -.53 .45 .37 Body Weight .13 .48 .66 .08 Milk Prod. -.13 .56 -.43 -.39 Lactation No. .50 -.59 .47 .26

t/l op l=! ~ Ca .42 -.43 -.36 -.18 0

-.57 .02 .40 .02 a P 0 CalP .73 -.26 -.45 -.05 t)

rg Hematocrit .06 -.59 .69 . .33 0 M I.:Q

Q)

.!.:l • ~ Crude Protel.n -.10 .61 -.22 -.40 s:: Ca -.21 -.58 -.30 -.37 H

'd P -.10 .64 -.)7 -.28 Q) Q) CalP -.11 -.49 .44 .01 Ji:.t

.fl ENE -.08 .70 .06 . -.)0 1-' t/l N

I%.l Cl'.

* . Significant at P ~.05 **. .. . Sl.gnl.fl.cant at p,;<. 01

....... ' .. -J

,/

Table 18. Simple Correlations of Services per Conception and Calving Interva1s with other Parameters. (Trinidad Herds).

Meré'[ No. l Herd No. 2 Herd No. î Variables Services Ca1ving Services Ca1ving Services Ca1ving Compared per Interval per Interva1 per Interva1

QQDg ell:t ion Conce12tion Conce12tion

Age -.05 -.16 .30 .28 .52 .44 .26 * -.26 Body Weight .30 .67 .28 .20

Mi1k Prod. .66** .44 .41 .33 -.06 .05 Lactation No. -.25 -.28 -.05 -.44 -.39 -.13

(Il

1:1 * * Cl)

-.26 § Ca .41 .56 -.60 -.06 .09 El P .01 -.10 .45 .18 .32 .16 S CalP .23 .44 -.61 * -.18 -.26 -.09 "d Hematocrit -·30 -.23 -.23 -.34 -.06 .09 0 0

1"""1 !XI

Cl)

~ 6 ** * ** aS Crude Protein • a .50 .70 .37 -.20 .19 ~ Ca .74** .46* .45 .23 -.13 .17 H

* .42 "d P .50 .51 .31 -.52 -.11 Cl)

* Cl) CalP .31 .02 .01 -.20 .70 .44 J%..

...s ENE * .* .65* ·55 .47 .32 -.24 .19 1-'

(Il N P::1 -.,J

"

.. ~ "ï .. ..J

,0-" ,;-'

Table 18 Cont'd

Herd No. li Herd No. () Herd No. 2 Variables Services Calving Services Calving Services Calving Compared per Interval per Interval per Interval

Conception Conce}2tion Conce}2tion

Age .15 .16 -.19 .4) .07 -.24 Body Weight .21 .12 -.28 -.1) -.07 -.06 Mi1k Prod. .05 -.03 .20 8 ** • 1 -.14 -.26 Lactation No. -.16 -.11 -.)7 .22 -.24 -.48

tIl ~ s:: Q)

.40 -.14 6** s:: Ca œ)2 .05 .7 .)8 0

a P -051 -.45 .05 -.24 .)5 .40 0 * * 0 CalP .6) .6) -.10 .28 .58 .21 'tj Hematocrit -œ)9 -.)) -.18 .05 -.28 -.02 0 0 r-i f]:I

Q)

..!.:l Crude Protein .27 __ , .14 -.1) .24 -.02 «1 -.10 op

.64* t:i Ca -.04 -.21 .0) -.06 -.06 'tj P Q)

.29 .22 -.04 .64~ -.01 -.18 Q) CalP -.)8 -.40 .13 -.04 -.05 .42 lit

fS ENE .18 .09 -.17 .19 -.08 -.1) 1-' tIl p;:J l\)

CP

'. 1

,r_.-.

Table 18 Cont'd.

Herd No. 7 Herd No. 8 --~-~----~HeraN00

Variables Services Calving Services Calving Services Calving Compared per Interval per Interval per Interval

Conception Conception Conception

Age -.18 .00 .46 .10 -.14 -.19 . 4 8 ** 4* Body WeJ.ght .09 .0 .19 - .25 • 2 .7

Milk Prod. .48 .57* .52 .13 -.20 -.45 Lactation No. -.47 -.24 .39 .12

{/)

~ ~Ca .01 .04 -.24 -.19 -.19 .... 14 o aP .05 -.04 -.30 -.14 -.04 .... 23 SCalP .03 .12 -.08 -.09 -.05 .16

'g Hematocri t .09 .09 .01 - .02 - .39 - .33 o r-l Il:!

CI)

~Crude Protein .40 .40 .29 -.04 .59 .39 ~ ~ Ca .21 .39 .35 .14 .03 - .23 H * * 'tj P .59 .67 .41 .16 - .28 - .35 CI)

CI) Ca 1 P - .48 - .35 .12 .11 .53 .27 I%.t +' ENE .28 .25 .32 - .15 .54 .35 {/)

~ ~ 1\) ~

',,- -.

Table 18 Cont'd. --- ----- -- ----~

Herd No. 10 Herd No. Il Herd No. 12 Variables Services Calving Services Calving Services Calving Compared per Interval per Interval per Interval

Conception Conception Conception

Age .18 -.ll1! -.19 .07 Body Weight .49 * -.36 .16 .27 Milk Prod. .01 .68**

Lactation No. -.41 .09

CIl ~ ,:::

-.66** ~ Ca .16 - • .51 -.24 0

s P -.09 .02 .4.5 -.04 * 0 CalP .11 -.33 - • .56 -.16 0

"d Hematocrit .23 -.28 .06 .24 0 0 r-I I:Q

Q)

~ Crude Protein * -.14 al .13 -.21 • .5.5 ~ * .fi Ca .06 .04 • .59 -.07 "d P .11 .04 .64* -.20 Q) Q) CalP -.28 .02 -.18 .36 rz.. • ENE .24 -.28 .42 -.06 ...... ~

CIl \.,A)

~ 0

-l

...... ~ ....... '\ -', ."

Table 18 Cont'd •

Variables Compared

Herd No .13 HerdNo. -14 - Herd No. 15 Services Calving Services Calving Services Ca1ving

per Interval per Interval per Interval ConceptiQu_________ Conception Conception

Age Body Weight Milk Prod. Lactation No.

Ca

el P 0 CalP 0

'& Hematocrit 0 roi ~

(1)

~ l'tf Crude Protein ~ t:: Ca H

't:I P (1) (1) CalP lJ:i • ~ ENE (Il Il:l

-.48 -.04

.29

.07

.18 -.21

-.10 -.26 -.18 -.14 -.14

.42 .31 .42

.81** .71 ** .01 ** 4** .77 .7

-.09 -.24

.27 .00 .05

.19 .09 .40

.00 -.13 -.31 -.11 -.07 -.11

.88** 8 *'* • 3 .00

.88** 8 ** • 2 -.33 ** 8 ** .75 • 1 -.33

* -.33 -.54 .00 .89** .81** .01 1-'

\..> 1-' - ,

. ...1

r',

Table 18 Cont'd.

Herd No. lb Herd No. 12 Herd No. lB Variables Services Calving Services Calving Services Calving Cornpared per Interval per Interval per Interval

Conception Conception Conception

Age .40 .36 -.06 .60 * .18 Body Weight -.09 .11 -.32 -.53 -.13

* Milk Prod. .31 -.08 -.64 -.43 Lactation No. .00 -.47 .37 -.43

(/) op $:l

~ Ca -.16 .04 ·33 .07 .44 0 sP .04 .08 -.17 .02 -.01 0 CalP -.18 .03 .37 .07 .28 0

'0 Hernatocrit .35 .48 .40 -.45 -.37 0 0 ri p::j

Q) ,!4 Crude Protein ** as .00 .09 -.39 -.80 -·35 op * $:l Ca .00 .14 -.29 -.72 -.40 H

'd P Q)

.00 .24 ** -.?2 -.74 -.20 Q) CalP .00 -.35 -.02 .40 -.20 l'ti • ENE .00 -.76** op .15 -.30 -.29 (/)

r:iI ..... ~ l\)

'-1

, ............. ( . ,"

~,~ .. --

Table 18 Cont'd.

Herd No. 12 Herd No. 20 Herd No. 21 Variables Services Calving Services Calving Services Calving Compared per Interval per Interval per Interval

Conception Conception Conception

** .34 .14 Age .91 -.13 -.30 .13 Body Weight .01 .50 .21 -.05 -.44 -.40 Milk Prod. .01 -.17 .:37 .26 .02 .12 Lactation No. .33 -.03 -.39 -.10 .03 -.07 • tIl

~ * * Q.) -.24 ~ Ca ~.15 -.21 -.19 .72 .78

0

sP .54 .09 -.05 -.36 .29 .33 0 CalP -.50 -.33 -.17 -.03 .23 .25 0

'g Hematocri t -.20 " .36 -.28 -·33 .11 -.20 0 r-I çq

Q.)

~ Crude Protein -.04 .38 .32 .23 .06 .15 op

.1a .40 -.04 ~ Ca .22 .23 .07 H

'd P .03 -.07 .48 .33 .15 .23 Q.)

.44 -.46 Q.) CalP .34 -.40 -.21 -.15 P:.t • ENE .01 .42 op .30 .05 -.29 -.20 1-' tIl rx:I \".)

\".)

'-.

-,r

(' ., . \ ..--' , .

Table 18 Cont'd.

Herd No. 24 Herd No. 22 Herd No. 2J Variables Services Calving Services Calving Services Ca1ving Compared per Interva1 per Interva1 per Interval

Conception Conception Conception

Age .21 -.22 .86** .07 -.48 -.35 Body Weight .28 .36 .49 .07 .00 .05 Milk Prod. .47 .65 * .06 -.36 -.14 -.24 Lactation No. -.22 -.39 .39 -.45 * -.39 -.61

{Il f.l ~

~ Ca .47 .30 .27 -.17 -.21 .24 op .08 * -.09 .17 -.05 .37 .63 s 0 Ca .37 .10 .31 -.20 -.38 -.21 0

"d Hematocrit -.30 .18 .45 -.05 .41 .37 0 0 r-I ~

Q) ~ Crude Protein .40 .55 -.11 .31 -.05 -.06 CI1 f.l

.47 .64* ~ Ca .30 -.20 -.03 -.25 "d P .29 .49 .20 -.27 -.04 .01 Q)

.08 -.45 Q) CalP .2) .12 .20 -.02 r:r.. • ENE .39 .53 .45 -.01 -.05 -.04 op

{Il .... lïI \;IJ

~

j

~._-"

r '

Table 18 Cont'd.

Herd No. 25 Herd No. 20 Herd No. 21 Variables Services Ca1ving Services Ca1ving Services Ca1ving Compared per Interva1 per Interva1 per Interva1

Conception Conception ConceEtion

Age .25 .40 -.21 .05 .07 .37 Body Weight .35 .34 .46 .34 .38 -.31 Mi1k Prod. .32 .56 -.07 -.15 .28 -.08 Lactation No. -.03 -.39 -.33 -.01 .00 -.63 *

ID op s::: ~ Ca .15 .15 -.42 -.52 .00 -.45 op -.14 .40 ** -.17 .19 -.03 -.76 a 0 CalP .22 .21 -.41 -.63 .01 -.21 0

ro Hematocrit -.05 -.27 0

.09 .02 0.4 -.32 0 r-I J:Q

Q)

!!III Crude Protein .43 .49 .38 .22 .36 tG -.20 op s::: Ca .30 .55 -.11 -.22 .51 -.12 H

ro P .24 .53 .21 .05 .12 -.26 Q)

* Q) CalP .28 .28 -.45 ~ -.35 .70 .15 • op ENE .40 .52 .39 .26 .38 -.25 (Il

l':iI 1-' 'vJ \..Il

\ ;-' • 1

Table 18 Cont'd.

Herd No. 28 Herd No·. 22 Herd No. JO Variables Services Ca1ving Services Ca1ving Services Ca1vlng Compared per Interva1 per Interva1 peI' Interva1

Conception Conception Conception

Age .07 -.24 .47 .35 -.29 -.48 Body Weight -.42 .37: .45 .14 ** -.73 -.09 Mi1k Prod. -.12 -.17 -.12 .25 -.01 -.12 Lactation No. -.11 -.66 * .29 -.21 -.15 -.70 *

fil op ~

~ Ca .09 .14 -.03 -.19 .39 .37 0 * sP -.67 -.55 .12 .20 .32 -.40 0 * -.09 0 CalP .57 .50 -.19 -.22 .50

"I:j Hematocrit -.12 .45 .10 .09 .68* .04 0 0 r-I (l:I

CI> .!r4 -.47 -.47 * «S Crude Protein .20 .11 -.65 -.11 t= Ca -.32 -.01 -.26 .23 -.23 -.09 H

.16 -.25 .25 * .08 "I:j P -.39 -.59 CI> CI> CalP .30 -.31 .18 -.18 .43 -.21 I%i .., -.40 .26 -.41 * 1-' ENE .19 -.62 .13 fil \..ù l'ii 0'\

* Significant .at P L .05 ** .•

S ignificant a t P <.. .01

;..J

( .. - ,

1)7

in herd )0 there is a highly significant negative correlation

between body weight and services per conception, indicating

that as these animaIs decrease in body weight they required

more services to conceive.

Many dairy cows in their first month or two of

lactation are in a special case of undernutrition as they

are usually in negative energy balance even when offered

liberaJ. amounts of an adequate diet. When animaIs are

maintained on pasture a further complication arises, because,

although they May or May not be losing weight, they could be

on the border line of deficiency of any number of nutrients

from day to day (Lamond , 1970).

Under the section dealing with feed intake it was

pointed out that herd )0 was in negative energy and

phosphorous balance, and it also had an imbalanced calcium.

phosphorous ratio intake so that a combination of aIl these

deficiencies May be in part responsible for its infertility

prob1ems.

The significance of increase services per conception

with increasing body weight in herds 9, 10 and 14 is not

c1ear since it is inconceivab1e that the animaIs could be

becoming fat and so hindering conception.

c. Milk Production

In herds E, F and l (Quebec) there is a significant

correlation between services per conception and daily milk

138

production. The very high significance shown in herd l may

be reflected in the high negative energy and protein balance

observed (Table 14) so that if the animaIs continue to

produce reasonably weIl they would be drawing on body

reserves, thereby creating body conditions less than

favourable for high conception.

Herds 1 and 14 rank among the highest producers in

the Trinidad herds and the high correlation between production

and services per conception observed is in agreement with

Morrow ~ gl. (1966) and Davidson (1969). The findings of

Morrow ~ al. (1966),that selection for high milk production

also significantly increases the mean services per conception

and calving interval in the United states,can be applicable

to these herds,since under tropical conditions higher

producing dairy animaIs experience greater stress than low

producers.

The significant negative correlation between services

per conception and milk production observed in herd 18 may

indicate that there is an optimum level of production

compatible with high conception since herd 18 is the lowest

producer among aIl herds.

The significant positive correlation between calving

intervals and production level observed in herds 14 and 22

may also be.related to observations made by Morrow et al.

(1966), since these two herds are also in the highest

lJ9

producing groups. However, the relevance of such significance

shown by herds 5, 7 and Il is not clear since these herds are

among the lowest producers.

d. Lactation Sequence (Number)

There were no significant correlations between services

per conception and lactation sequence (number) in any of the

herds. However, there was a significant negative correlation

between lactation sequence and calving intervals observed in

herds 24, 27, 28 and JO (Table 18). This would indicate

that a shortening of the length of calving intervals would

increase thenumber of lactations in each herd. This would

be in keeping with accepted dairying principle. Table 6

shows the very long calving intervals associated with these

herds.

e. Blood Components

i. Serum Calcium

Comparing aIl herds, a negative but significant

correla.tion was observed between services per conception

and serum calcium level for Herds D and H (Table 17) and 2

(Table 18). Since the herds involved are weIl within the

accepted range for normal serum calcium levels (Tables 8 and 9)

these varying results May indicate that under the different

management regimes, each animal in each herd may possess its

own calcium serum level compatible with high fertility.

140

The close association between services per conception

and calving interval rnay be reflected in the sirnilar pattern

of a significant but negative correlation between calving

interval and serum calcium in herds H (Table 17) and Il

(Table 18) and in herds 1 and 21 (Table 18) with a significant

and positive correlation.

ii. Phosphorous

Within the Quebec herds (Table 17) with the exception

of herd H there are no significant correlations between

serum inorganic phosphorous and services per conception and

calving interval. The high correlations observed between blood

components and services per conception and calving interval

in herd H May be indicative of this herd possessing the

ideal calving interval of 367 days although an improvement

could be achieved in a better conception than the present

2.7 services (Table 5).

The trend observed in the Quebec herds was almost

identical for those in Trinidad. The only exception being

in herds 24 and 27 (Table 18) where a high positive and high

negative correlation respectively existed between serum

inorganic phosphorous and calving interval and in hérd 28

a high negative correlation existed between services per

conception and serum inorganic phosphorous.

Again these observations May be indicative of the

individual animal in each he rd possessing its own level

,,-._,'

141

of blood constituent compatible with conditions for optimum

conception.

iii. Hematocrit

With the exception of herds C (Table 17) and JO

Table (18) there is no significant correlation between

Hematocrit (Packed Cell VOlume) and services per conception.

The significance of the high negative correlation observed

in herd C indicates that as per cent volume of blood decreases

services per conception increase. The significance of the

relevance of the high positive correlation observed in herd

JO cannot be ascertained since PCV for herd JO is below the

normal Mean (Table 9).

There is no significant correlation between calving

interval and Hematocrit values.

f. Feed Intake

Of great importance is the high significant positive

correlation shown between protein, calcium, phosphorous and

energy intake with services per conception observed in Herd l

(Table 17). These results, if taken literally would be quite

misleading, since the indication would be that by increasing

the nutrients services per conception would also increase.

However, Table 14 shows that this herd is both in a negative

energy and protein balance. Of aIl the Quebec herds, Herd l

exhibits the MOSt services per conception (J.2 ± 0.9) ~nd

1

t ."

\ ... )

142

fairly long calving intervals (406 ± 15.4 days). One

possible interpretation is that the farmer is overfeeding

his high producing cows whereas the low producers are

underfed.

In herd G (Table 14) there is a high negative

correlation and a high positive correlation between phosphorous

intake and calciumlphosphorous ratio respectively, and services

per conception. This would be in agreement with Hignett and

Hignett (1952) and Steevens ~ âl. (1971) who found that a

larger number of services per conception was required when

the phosphorous intake was low.

Within the Trinidad group (Table 18) an almost

identical situation to that observed in Herd l (Quebec) exists

in herds 1 and 14. These two herds show a high significant

positive correlation between services per conception and

ca1ving interval and the intake of energy, protein, calcium

and phosphorous, the situation being more acute in herd 14~

An examination of Tables 6 and 14 indicates the infertility

prob1em of herd 14 and the deficiency in nutrients intake in

both herds. The positive correlation would indicate that as

nutrients intake increase there would be a concomitant

increase in inferti1ity problems - a MOSt unlikely situation.

A possible, but inconclusive explanation is that the ~armers

were overfeeding the high producing cows and underfeeding the

low producers.

The highly significant but negative correlation

Î

existing between protein, energy, calcium and phosphorous

and services per conception in herd 18, and the high negative

correlation between prote in, energy and phosphorous and

services per conception shown in herd 30 are indicative of

the close association between nutrition and reproduction.

An increase in the specifie nutrient status in each herd

will increase the fertility status by a reduction in services

per conception. This would be in keeping with numerous

reports from nutritionists and veterinarians (Morrow, 1969;

Olds, 1969; Boyd, 1970; Lamond, 1970).

5. Summary of Simple Correlations between services per conception and calving intervals with other parameters.

a. Quebec Herds

Table 19 outlines the summary of correlations between

services per conception and calving intervals with other

parameters by grouping aIl Quebec herds and aIl Trinidad

herds separately, so that herd effects are eliminated.

With the exception of a negative but lowsignificant

correlation between lactation sequence and calving interval

there are no significant relationships between any of the

other parameters and reproduction in the Quebec cows.

This significant association between lactation sequence and

calving interval seem to indicate that the younger animaIs

were giving more problems than older ones. Verification of

such an interpretation will need further investigation.

.t.

Table 19. Summary of simple Correlations of Services per Conception and Calving Intervals with other Parameters. (Quebec Herds merged, Trinidad Herds merged, and the Government Herds Centeno, Trinidad).

Government Herds Quebec Herds Trinidad Herds P!brecf-}{():Lstein Crossbred

Variables Compared

Sere Calv. Sere Calv. Sert Calv. Sere Calv. per Inter. per Inter. per Inter. per Inter.

Concep. Concep. Concep. ___ Collcep. -(112) (90) (90) (427) (28) (28) (47) (29) (29) (107) ()5) ()5)

** * ** * Age Body Wt.

.00

-.11 Milk Prod.­Lact. No. -

CIl op

~ Ca §P {5 CalP o . '0 Hema' crl t g (PCV) r-! ~

Q)

-.0)

.06

-.05 .09

~Protein -.01 op r.::: Ca

H

'OP Q)

& CalP

+' ENE CIl

.02

.00

-.01

- .06

-.0)

-.18 .1)

-.0)

-.0)

.11 -.10 - .02

-.05 .02 .02

- .01

-.08 ~.

Numbers in parenthesis ~~ . ..

Slgnlflcant at P <.05 ~H.. .. < Slgnlflcant at P .01

-.18

.19 .18 .14 .16 .09 -.09 .28 -.07 .21 .)8

** * .18 .08 .06 .20 .04 .)6 .08

-.24*

.05

.04

.01

.01

.14

.16

.01

.09

.18

.02

.04· -.02 -.02

* .10 2 ** • 0 .10~·

.06

.21 ~.~.

.15 -.1)

.07

.08 -.00

-.10

-.02

~~

*

8** .1 -.00

.10

.10

.08 -.12

-.00 .01 .00

* -.12

.17**

.20**

-.02 .16** .16~H.

indicate number of observations

-.09 -.1)

.10 i~

.29

-.12 -.)8*

-.28 -.11

.0)

.29

.17 .00

.14 -.02 ,14 -.08

- ,13 .10

.17 .01

.24

-.09

.16

.02

.07 -.)0

.45*

.4)*

.27

.33

.42~·

-.1)

**

-.04 .40*

-.20

.22 .21 -.01 .04

.19 .22 -.01 -.11

-.10 -.06

- ,06

- .03 -.11

.2)

.)6*

.40*

-,16

.13

-.12 .16 .0)

-.0)

-.12 .06

-.09

.00

.04

.22

-.37*

-.04 ~

n , .;~

\ \

145

The low relationships between services per conception

and calving intervals with the other parameters examined is

an indication that management, which embodies almost every

aspect in dairy farming, was responsible for the wider

variations observed in individual herds. As a result of

removing or masking these individual herd effects, a more

uniform picture of relationships is then presented.

b. Trinidad Herds

In the Trinidad group the significant relationships

observed are mainly due to the large number of observations

involved so the relevance of these significance is

indeterminable since the "r" values are so small.

However, there is an indication that as the animaIs

become older services per conception increase and calving

intervals increase. Again this is in agreement with findings

of Davidson (1969) for animaIs in Trinidad.

The significant relationship between lactation

sequence and service~ per conception and calving intervals

is basically in agreement with expectation, and in keeping

with acknowledged dairy findings where fertility of cows

decrease with advancing age. Foley et al. (1972) reported

that fertility in dairy cows increases up to 4 years of age,

remains constant to 6 years, then gradually decreases with

advancing age.

The apparent difference in relationship between age

146

and calving interval observed in the Quebec group May be

due to the culling procedure whereby infertile animaIs are

culled before they get old.

A previous observation in herds 1 and 14, (Table 18)

where significant positive relationships exist between

services per conception and calving interval and crude protein,

energy, calcium and phosphorous intake, is manifest when

herd effects in the Trinidad group are eliminated. The MOSt

logical and important consideration seem to indicate that

high producing cows were very weIl fed and the low producers

were getting below requirements.

c. Government Herd (Trinidad)

i. Purebred Holstein

Hematocrit value has a significant positive relationship

with services per conception. The significance of this is

not clear. An examination of the Hematocrit value (Table 10)

indicates that the mean of 30$2 + 0~5 % volume is below the

Mean of the normal range.

The sii,nificant positive relationship observed between

body weight, crude protein, calcium and energy intake, and

calving interval May be explained in the same light of over­

feeding of high producing cows and underfeeding low producers.

ii. Crossbred HOlstein/Zebu

A significant positive correlation exists between level

of production, calcium and phosphorous intake and services

1

(

147

per conception. The positive relationship between high

production and calving intervals agrees with the findings

of Morrow et gl. (1966) and Davidson (1969). Despite the

fact that Morrow et al. findings were in the United States

extrapolation of their data to tropical conditions may be

still relevant although the ceiling at which the relationship

exists may vary significantly.

Numerous authors have indicated that a phosphorous

deficiency affects reproduction in the dairy cattle

(Eckles et al., 1932, Eckles ~ al., 1935; Hignett and

Hignett, 1952; Morrow, 1969). The positive relationship

between phosphorous and services per conception and between

calcium and services per conception is contradictory to

these reports. There was a negative relationship between

services per conception and calciumaphosphorous ratio.

In summary the relationship between infertility as

measured by services per conception and calving intervals,

and various parameters have raised some interesting issues,

particularly where the Trinidad herds were concerned. For

example, are the farmers really over-feeding high producers

at the expense of low producers, thereby increasing the

infertility problem? And is the Government Cros~bred herd

at Centeno getting too much mineraIs or is there a lower

requirement for animaIs of the Zebu crosses compatible with

high fertility? Are the nutrient requirements for cattle of

Temperate Zone areas applicable to animaIs in the Tropics?

--, .

The significance of these results will require further

controlled investigations.

148

6. A Comparison of Means of different Parameters between Quebec and AlI Trinidad Herds

A comparison of the means of the various parameters

examined in the different localities are set out in Table 20.

Herds have been combined to eliminate individual herd effects.

a. Body Weight

~he Mean body weight of the Quebec herds is roughly

88 kg higher than the Trinidad herds and roughly 4 months

older. The body weight of the Quebec group is approximately

the same as the Government Purebred Holstein herd which is

about 6 months older. However, the body weight of the

Trinidad group is almost identical to that of the Government

Crossbred herd which is about 8 months younger.

b. Milk Production

The Mean daily production in the Quebec herds was

16.0 kg almost twice as much as the Trinidad herds

(8.9 kg daily), and the Government Purebred Holstein herd

(9.6 kg daily). However, the mean daily production of the

Government Crossbred/Zebu Holstein herd was 1.7 kg less than

the Purebred Holstein he rd under similar conditions of

management.

These results parallel reports by Mahadevan (1966),

Knudsen and Sohael (1970) and Mc Intyre (1971). These

t \

149

Table 20. A Comparison of Means of different Parameters between Quebec and Trinidad Herds.

Government Quebec Trinidad Purebred Crossbred Herds Herds Holstein Holstein

No. of 112 427 47 107 AnimaIs Age (Mths) 60.4 56.6 66.1 47.9 Body Weight 542.3 454.9 549.5 453.2

(kg) Mi1k Prod. 16.0(90) 8.9(283) 9.6(29) 7.9(35)

(kg) Lactation No. 3.0(90) 1.8(283) 2.4(29) 1.6(35)

B100d Ca(mg/l00 ml) 10.8 11.0 Il.2 Il.6 P (mg/100 ml) 5.3 6.6 6.1 6.3 Ca:P 2.1 1.7 1.8 1.8 Hematocrit 31.1 ,30.1 30.2 35.2 % volume

Intake Crude Protein 2.2 1.6 2.9 1.5

(kg) Ca (g) 112 57 85 39 P (g) 62 43 65 33 CalP 2.4 1.4 1.,3 1·3 ENE (Meal) 16.5 9.6 12.4 8.9

Services per 2.1 2.2 3.0 2.7 Conception Ca1ving 399.0(90) 437.2(283) 488.2(29) 435 (35) Interva1 (days)

Numbern in parenthesis indicate number of observations

; ,

150

workers found that animaIs imported from temperate regions

performed creditably when compared with those bred specially

for the tropical environment.

The performance of European-type dairy animaIs in

tropical regions has been studied by many workers (Wright,

1946; Payne and Hancock, 1957; Rice, 1965). Among the

general conclusions was that European-type animaIs did not

produce as much milk in the tropics as in the temperate

regions because of sub-standard plane of nutrition caused

by a seasonal variation in pasture in the tropics, associated

with marked differences in rainfall throughout the year. It

has also been suggested that European-type animaIs achieve

optimum production when daily temperatures lie between the

range of 10 to 2l.loC (Findlay, 1950) and thatthey are not

adapted to conditions where the mean annual temperature

exceeds 21.1oC (Wright, 1946).

These may be possible reasons for the low production

in Trinidad as compared to the herds in Quebec with animaIs

of similar origin and breed.

c. Blood Components

The serum calcium and Hematocrit values for the Quebec,

Trinidad and Government Purebred Herds showed very little

variation, however, the serum inorganic phosphorous was higher

in the animaIs in Trinidad.

The results for the blood components for the Government

151

Crossbred herd were higher than those for the Government

Purebred herd. These results are in agreement with those of

Davidson (1970) from the same Government herds, and with

Rusoff et al. (1951) and Blincoe et al. (1951) referred to

earlier.

d. Feed Intake

The general level of the components estimated in each

group is reflected by the level of production and chemical

composition of the concentrate and forage fed.

The difference in feed intake between the Government

Purebred Holstein and the Crossbred herd, where the

management for each herd is the same, is due to the better

managed pangola grass pasture offered to the Purebred herd

(Appendix Table 6). These pastures were recently fertilized

whereas those offered to the Crossbred herd were not at the

time of visite There May also be variations in soil nutrients

at the different locations in which each he rd is kept.

e. Lactation Sequence (Number)

It is interesting to note the difference in lactation

sequence between the Quebec herds and the Trinidad herds.

The Quebec herds have an average of 3 lactations compared

to the Trinidad group of 1.8 in animaIs of almost the sarne

age; and more than the Government herd (2.4) in animaIs

that are older. The results in the Crossbred he rd appear

slightly better. Many workers have reported that animaIs

152

in the tropics have their first calf at a very late age as

compared to 24-30 months in the temperate regions. Mahadevan

and Searle (1968) reported age at first calving in Barbados

as 33 months; in Trinidad the range was from 31-50 months

(Mahadevan et al.,1968); in Jamaica 33-42 months

(Wellington et al.,1970); and in many parts of Africa and

India the range was from 37-59 months (Mahadevan, 1966).

The age at first calving for the Crossbred herd at

Centeno was 39 months (Davidson 1969) so this can account for

the fewer number of lactations in this group.

The reasons for late maturing of animaIs under

tropical environment have been attributed to effects of

climate, differences in level of feeding and to parasites.

Broadly speaking, over a wide range of feeds used for

ruminants, voluntary feed intake declines as its digesti­

bility declines. It is no doubt true that with tropical

grasses voluntary feed intake is poorly related to digesti­

bility but a marked decline in intake occurs when the protein

content of the herbage dry matter falls below 7 per cent

(Milford and Minson, 1966).

Since the majority of the Holstein animaIs in Trinidad

were imported either as mature, or as heifers between the

ages of 9-14 months late m.aturity is almost ruled out.

However, other stress factors, such as climatic effects,

external (mainly ticks) and internaI parasites, and a

lowered plane of nutrition may account for the fewer calvings

and no doubt lower reproductive life observed in these

animaIs in Trinidad as compared to those in Quebec.

f. Index of Fertility

i. Services per Conception

153

The number of services required per conception in the

Trinidad herds (2.2) compares favourably with the results

from Quebec (2.1); whereas the Government Purebred herd

required almost 1 complete service more for each conception.

This difference in services per conception between the

Trinidad herds and the Trinidad Government herds is 1argely

a ref1ection of the use ·of "back up" bulls on the Trinidad

herds in cases of difficult breeders, whereas the Government

herd use A.I. exc1usive1y.

The Crossbred he rd required 0.3 services per conception

1ess than the Purebred herd, however, it wou1d seem that

its ferti1ity problem is increasing when compared to

Davidson's (1969) resu1ts of 1956-1966 of 2.5 services per

conception. This study included animaIs born in 1965 and

later.

Many services per conception can be attributed to

numerous causes. The reproductive function to be normal

requires perfect occurrence and synchronization of many

subfunctions and events in each sex (Zemjanis,1965). A

failure of any of these results in failure to conceive. In

addition to female and male infertility factors there are

154

many errors created at aIl levels of human interference.

Such factors as feeding and management of the herds, failure

to detect heat so that there is proper timing of service

which is the basis for successful mating. Errors in semen

processing, in treating of semen with antibiotics, in storing

and distribution of semen, inadequate insemination technique,

poor sanitation and unpredictability as far as availability

for service are aIl possible, and apparently occur in

Trinidad (Mills, 1969).

ii. Calving Interval

The calving interval for the Trinidad herds (437.2 days)

was 38 days longer than for the Quebec herds (399), or almost

two complete estrous cycles longer. However, the Trinidad

Government Purebred Holstein herd had an even longer calving

interval (488.2 days) than the Trinidad herds which was almost

the same as the Government Crossbred herd (435 days). Again

the fact that "back up" bulls are used on the Trinidad herds

will not only reduce services per conception but also the

resultant calving intervals.

Apart from this, Dav-idson (1969) reported that 75% of

both Government herds suffered frorn cystic ovaries, this no

doubt increase the incidence of infertility.

AlI these calving intervals are longer than the ideal

12 rnonths but the Quebec herds compare favourably with the

13.5 rnonths associated with Dairy Herd Irnprovernent data in

the United States (Pelissier, 1972).

,

155

ME\ny §lJ1ïhfH~IFl )1~Vê li\àVtH'l3.ted croesbreeding as a means

of reducing 1nrtnl'lj~.:I,:1.'IJ:y ;1,1'1 (J~ttls particularly under tropical

environmentêl wh€lt'~ (U~~tHlê, 611ml3.t:1o stress, and nutri tional

factors E\ff€H;,t fJ'3'hI1 'uh~ 1l:r6t1uot1on and fertili ty of cattle

of EuropeE\n QI'i~j:n.

If Wê làrê ,tif! Ut,:l~ 'bilé! (J(JVst'ntnent herde as an example

this idea mlàY fJ€l JUI\HJ1:t'J,fH\. Howevsr, we have seen the other

Trinidad n@I'Q§ (:t,mptH:"hl~(l §'btH;llt) potantially doing as weIl as

the cross'b:r.êQ§.

A numlH?I' @;f,' !t'Ml'lltm13 ()§.tl he reeponsible for long

cal ving intêt'V{ܧ. Ut;l:l.t;\~êlÏ ~ lt'él'lJ service or service interval

alone acoountêd ;rOJil :tri 1 U~~ Q~I 'llhê! variance of the interval

from partu:r.iti~m 'lm éH)1l\'.lêJ)'b1611. (Touohberry II §.l •• 1959) •

Mahadevan (l~QQ ~ ~ 'li'ln\l'lHI'U€ltl l3êliléJOtlal variations in feed

supply in t:r.gplf:lۆ CI fi 'II 'li:l. li:! l:'\13 Il ttll3.jor factor influencing

length of thê 13êirV,tt}@ 'Pt,n:'~1.I:Hl,

Fai.l.wrê 'b~ dê'lilH~'IJ O(}W13 11'1 heat saon enough after

calving WE\§ :r.ê§Fon§it\):Ll~ :t'O:fl 13. lfil3.jor portion of delayed first

services, mi§§êG h~t:\'b JIt:wj,t'ltl§ ë\dded to the seriousness of

the problem (fêl1§§&~~, 19?1).

Whi1.ê g'blH~\t' Q~UI;\I;!I3 §Uf.)ft 13.13 ambryonic death, retained

placentas, IànQ rty§'lil)();\,~.\ ooultl ë\tH~t)urtt for longer cal ving

intervals j,t Wf:nürt AllJ.)~~\~;\ 'tlh~t mil3sed heat periods were

responsibl~ fQt' 'th§ l\)H~!:~~i\ ~~lv11'1g intervals in the Trinidad

herds whose §ê:r.\fj,Q~~ P~"" OOflt'Jêptiotl were almost identical to .

those in QuePêQ. \r.l\tl tHt'~l\Ë'ml3 vl3.t'1a tion between herds (Table 6)

156

is an indication that many of the dairy farmers can improve

the breeding efficiency of their herds by concentration on

the problem more seriously. This is particularly so in

reference to estrous detection.

It appears that ~he calving interval is primarily a

management decision with the length of the calving interval

depending largely en the dairy farmers' ~ttitudes and ability

to detect heat since short heat periods,often during the

night, and silent heat periods make heat detection difficult

with many cows.

7. Evaluation of effects of production parameters on fertility index. Herd effects removed.

Tables 21 and 22 outline the mean effects of lactation

number on services per conception and calving interval for

Quebec and Trinidad herds respectively.

In the Quebec herds the lactation number dges not

seem to have any effect on the services per conception,

however, there is a steady decrease in calving interval

(exception second lactation) with each succeeding lactation.

This may indicate an earlier detection of estrus through

the farmers' better awareness of estrous expression as the

animaIs get older.

Within the Trinidad herds a more interesting picture

is unfold in that with each succeeding lactation there is a

progressive decrease in both services per conception and

157

Table 21. Means of services per conception and calving interval according to lactation sequence. (Quebec Herds).

Lactation No.

1

2

3 4

No. of Obs.

17 24

22 27

Services per Conception

Calving Interval

(days) 405 418

397 380

Table 22. Means of services per conception and calving interval according to lactation sequence. (Trinidad Herds).

Lactation No.

1

2

3

No. of Obs.

105 118

49

Services per Conception

2.5 2.1 1.8

Calving Interval

( days)

443 440 407

158

calving interval (Table 22). Three possible reasons, either

acting singly or in combination with each other, May account

for this development. Firstly, these imported animaIs May

be becoming adapted or building up some resistance to the

effects of tick borne disease and the rigours of a tropical

environment. Secondly, the practice of early removal of

problem animaIs May be giving a biased representation of the

exact situation. A third and equally, if not the most

logical explanation lies in the experience acquired by these

farmers both in the earlier detection of estrus and in the

general management and care of these animaIs.

The least squares estimates (Tables 23 and 24) were

computed to provide some indication of the effects of

lactation on services per conception and calving interval

in both the Quebec and Trinidad herd~. These estimates

indicate that after the fourth lactation there is a slight

increase in services per conception in the Quebec herds.

However, the Mean calving interval continues to decline due

to better heat detection.

In the Trinidad group the estima tes indicate a

progressive increase in fertility both in a lowered Mean

service per conception (a decrease by 0.31 services from the

mean) and calving interval (decrease by 47.2 days from the

Mean) after the third lactation. The reasons given for the

increase in fertility for the actual lactation means will

also hold for these estimates.

159

Table 23. Least Squares Estimates of the effects of lactation sequence on services per conception and ca1ving interva1. (Quebec Herds).

. ..

Lactation No. No. of Obs. Services per Ca1ving Conception Interva1

~da~s ~

1 17 +0.20 -4.9 2 24 -0.17 +24.3

3 22 -0.04 -4.0 4 27 +0.01 -15.6

Table 24. Least Squares Estirnates of the effects of lactation sequence on services per conception and ca1ving interva1. (Trinidad Herds).

Lactation No. No. of Obs. Services per Ca1ving Conception Interva1

,da~s~

1 105 +0.44 +48.7 2 118 -0.13 -1.5 3 49 -0.31 -47.2

160

The analysis of variance for the services per

conception (Appendix Tables 9 and 10) shows that there were

highly significant differences (P~O.Ol) between yield and

services per conception (Quebec herds) and between lactation

sequence and services per conception (Trinidad herds). The

significant differences between yield and services per

conception observed in the Quebec herds is in agreement with

the report by Morrow et al. (1966) who found that high

producing cows required significantly (PC:O.05) more services

than the lower producing ones.

The analysis of variance for calving interval

(Appendix Table 12) indicates that there is a highly

significant difference (P~O.Ol) between lac.tation sequence

and calving interval (Trinidad herds) and a significant

difference (P~0.05) between crude protein intake and

calving interval (Quebec herds). These significant

differences between lactation sequence and calving interval

and services per conception in the Trinidad herds can be

explained in the same manner as was previously done for the

actual means. However, it is questionable whether the

significant difference observed between crude protein intake

and calving interval (Quebec) is meaningful since there was

no correlation between these two parameters when herd

effects were removed.

Least squares estimates of the effects of services

per conception on the various productive parameters examined

161

in this study are presented in Tables 25, 26 and 27 for the

Quebec, Trinidad and Government herds respectively. There

is no consistent picture observed between calving intervals

and lactation sequence in the Quebec herds. This inconsisten­

cy may be due to the method of sampling plus the fact that

animals not yet having a calf are not included. The variation

from the mean of 29 days between animaIs requiring 1 service

per conception and those requiring 4 services per conception

is really not what would be expected. However, milk yield

shows a definite trend, increasing steadily as the number

of services increase. Since the feed intake for aIl herds

were based on production the trend observed for production

was indicative, and in fact was the case, for feed intake.

In the Trinidad herds the trend for an increase in

calving interval and a decrease in lactation sequence as

services per conception increase from 1 to 4 is in agreement

with what was expected. However, the wide differences

between lst and 4th services and 3rd and 4th services of

176 and 95 days respectively can be due to improper heat

detection, silent estrus, early embryonic death, abortions

or a combination of these symptoms. The differences between

lst service and 2nd service and between 2nd and 3rd service

of 38 and 43 days respectively, would indicate that the

problem lies mainly in improper heat detection, since

exactly one heat period has been missed. There is some

inconsistency in milk yield between the 2nd and 3rd services.

Table 25. \ Least Squares Estimates of the effects of services per conception on various productive parameters. (Quebec Herds).

Feed Intake Services Calving Milk Lact. Crude Calcium Phosph. Energy

per Interval Yield Seq. Protein Conception (days) ()05 days) (g) (g) (g) (Mcal)

kg

1 -15 -)1) +0.02 --:38 -1 -2 -0.06 2 - 9 -180 -0.02 - 7 -0·3 -1 +0.11

3 +10 + 59 +0.11 -20 -0.6 -1 -0.27 4 +14 +434 -0.12 +65 +2 +4 +0.21

Means 399 4895 3.0 2438 126 74 18.3

" .... -

Ca,P Ratio

+0.01 -0.02 +0.04 -0.03 1.8

1-' 0-. 1\)

Table 26. Least Squares Estimates of the effects of services per conception on various productive parameters. (Trinidad Herds).

Feed Intake Services Calving Mi1k Lact. Crude Calcium Phosph. Energy

per Interval Yield Seq. Protein Conception (days) (305 days) Cg) (g) Cg) (Meal)

kg

1 -74 -247 +0.08 -83 -6 -4 -0.4 2 -36 + 88 +0.19 +37 +2 +2 +0.2

3 + 7 - 26 -0.01 -23 -1 -0.7 -0.2 4 +102 +186 -0.3 +70 +5 +3 +0.3

Means 437 2746 1.7 1826 70 52 10·3

CalP Ratio

-0.2 +0.03 +0.01 -0.02 1.4

1-' 0'. \.Al

Table 27.

Services per

Conception

l 2

3 4

Means

Least Squares Estimates of the effects of services per conception on various productive parameters. (Trinidad Government Herds).

Feed Intake Calving Milk Lact. Crude Calcium Phosph. Energy Interval Yield Seq. Protein

(days) (305 days) (g) (g) (g) (Meal) kg;

-24 -289 +0.3 -79 -6 -6 -0.4 -47 -226 +0.1 + 8 -0 -0 +0.2 +29 +129 -0.02 +14 +3 +1 +0.03 +49 +182 -0.4 +56 +3 +5 +0.2 459 2653 2.0 2463 86 68 12.3

CalP Ratio

+0.03 -0.01 +0.02 -0.04 1.3

1-' (J\ -{:"

165

In the Government herd, with the exception of the

2nd calving interval, there is uniformity in increasing

calving interval, increasing milk yield and decrease in

lactation sequence as services per conception increase.

The difference in 73 days between lst and 4th service shows

that heat expression and detection are more consistent and

theproblem here could be related to proper time of

insemination, quality of semen, to the A.I. operator's

competence or to physiologica1 abnorma1ities of the cows.

8. Relationship between freguency of calvingsand rainfall, temperature and season of the year. (Trinidad)

Figure .4 out1ines the number of calvings according ·12

to month from 1965 to May 1971, a 30 year rainfal1 period

plus me an temperatures3for Trinidad.

The majority of the calvings take place from January

to May which is the period of the dry season. It would

appear therefore, that the months of June to October wh en

the calving rate is low, are the best months for conception

to occur. The peak of the rainy season also occurs during

the latter months. At this time the pastures are young and

rapidly growing and are richer in prote in.

Many authors have reported that in the rainy season

the crude protein content of weIl managed pangola grass

IIndividua1 cow records from aIl Trinidad herds and the Trinidad Government herds.

2Land Capability Survey of Trinidad and Tobago No. 3, Government Printery, Trinidad and Tobago. 1966.

3Government Meteorologica1 Station, Piarco, Trinidad.

166

Figure 4. Re1ationship between frequency of ca1vings and rainfa11, temperature and season of the year.

Il:.t o

,..... •

tIl H ~

0 C""\ .......

...-.. •

tIl 1=:

.r-f ....... ri ri

CG

ca .r-f

CG Il::

......... ri c--

'" ri

12

10

8

6

4

2

~ 140 ~ 1 120

::f' 100 '" ri '-'"

tIl 80

~ .r-f 60 ::-ri CG o

lWaximum .----. ----1 1 J ~------------ ,-----, ---. 1 --- 1---__ L 1 1 -------..,-___ J

Minimum

.L.-.---J.--

Jan Feb Mar Ap May Jun Jul Aug Sep Oct Nov Dec

. \

167

pastures can be relatively high, ranging from 12 - 20,%,

whereas in the dry season crude protein content falls to

as low as 4 - 5% (Butterworth et âl., 1961; Grieve and

OSbourn, 1965; Creek, 1967).

Results of this study (Appendix Table 6) are in close

agreement with the relatively high protein content during

the rainy season.

The mineraI content of grasses in the young succulent

state is usually adequate but, particularly phosphorous,

declines with the maturity of the forage.

Generally the feeding value of pastures in the rainy

season is higher than in the dry season. The apparent

higher conception of cows during the rainy season then may

be attributed to the overall better supply of nutrients

from forage sources.

The variation in the high environmental temperatures

is very small and seem to have no effect on the number of

calvings. Many reports indicate that conception rates are

usually affectedby high environmental temperatures and

humidities by causing a deterioration in semen quality in

bulls (Johnston et âl., 1963), lower fertilization rates,

and embryonic mortalities (Ulberg, 1958; Kelly and Hurst,

1963; Mc Intyre, 1971).

However, Mahadevan (1966) and Payne (1970) indicate

that the effects of high environmenta1 temperatures and

humidity on ferti1ity are 1ess severe in high altitudes and

168

maritime areas.

The results of this study may be indicative of the

maritime influences on temperature since the trade winds

from the Atlantic ocean tend to minimise these severe

effects.

. ,,",

! '-

169

VI. SUMMARY AND CONCLUSIONS

Although the main reason for this investigation

was an attempt to find whether there was a link between

feed quality, as laid down' by standards, and herd infertility,

it was felt desirable to deriye as much information as

possible from the results.

Eleven herds, with ten animaIs representative of each

herd, from the Province of Quebec, and thirty herds - rang~ng

from 10 to 21 animaIs per herd, from Trinidad plus a

Trinidad Government Purebred Holstein and a Crossbred

Holstei~Zebu herd were used in the study.

The overall fertility rate in the herds in Trinidad

was low, being 47.7% in the Trinidad herds (Crown Lands

Farms), 34.0% for the Purebred Holstein, and 39.3% for the

Crossbred Holstei~Zebu herd for first service calvings

respectively.

Chemical analyses of the forages and concentrates

from both Quebec and Trinidad when compared to reported

analytical values for similar feeds, showed slight

varia tions •

With the exception of two herds Quebec, (herds C

and G) and three herds Trinidad (herds 12,13, lS),plus

aIl heifers on the Trinidad Government Station, aIl other

herds were in negative energy balance based on U.S. Nutrient

Requirements of Dairy Cattle (1971). Herd l (Quebec) was

170

also in negative protein balance, but aIl other herds were

adequately supplied. AlI herds were adequately supplied

with calcium intake but herds E (Quebec) and )0 (Trinidad)

were below their phosphorous requirements. The intake of

calcium to phosphorous ratio in most herds was weIl within,

or close to, the normally accepted range of 1-2.1 with the

exception of Herds Gand )0, ).7 and ).2 and herds K and 24,

0.8 and herd 8, of 0.9 to l ratio respectively.

Energy supply seem to be the limiting nutrient

during winter feeding in Quebec. The extent to which energy

supply is limiting in the Trinidad herds cannot be ascertained

since intakes were based on requirements associated with

temperate regions, and many reports indicate that both

environmental and physiological factors limit the feed intake

of ruminants in the tropics.

In aIl herds blood serum inorganic phosphorous and

serum calcium appeared weIl within the normal range,

however, there were more variations in the calcium.phospho­

rous ratio in the Quebec herds than in those in Trinidad,

due mainly to a greater variety of feedstuff grown in Quebec.

However, serum inorganic phosphorous was generally higher

in the Trinidad herds.

Mean Hematocrit (Packed Cell Volume) for aIl herds

was within the normal range, but 2 herds in Quebec and 8 in

Trinidad were close to the lowèr range. It was assumed that

both external (mainly Boophilus ticks) and internaI parasites

171

were mainly responsible for these lower values in the

Trinidad herds. The Mean Hematocrit values for the Crossbred

Holstein/Zebu herd were higher (35.2 + 0.4%) than in aIl

other groups.

In one herd in Quebec there was a significant

correlation (P<:O.Ol) between services per conception and

calcium, phosphorous, calciumaphosphorous ratio, and energy

intake. This was also true for 5 herds in Trinidad.

Significant correlations also existed between calving

interval and these nutrients intake in another five herds.

Generally, where milk production was high there was a

significant correlation (P<O.Ol) between services per

conception and milk production and between calving interval

and milk production.

These significant effects were not conclusive proo!

that he rd fertility was in tact impaired, because in some

herds with infertility problems this trend was not observed,

but was also seen in others of low infertility. This

indicates the great difficulty in determining the cause of

infertility in a herd, and May suggest, that further

controlled nutritional trials are required before any real

conclusions could be drawn, since the causes of infertility

May weIl be due to factors other than those under examination.

Services per conception between the Quebec herds

(herd effects removed) were almost identical to that observed

in the Trinidad herds (herd effects removed), (2.1 and 2.2).

However, the Government herds required slightly more

(3.0 and 2.7) services per conception for the Purebred

Holstein and the Crossbred Holstein/Zebu respectively.

172

The use of "back up" bulls in the Trinidad herds was

responsible for this difference in the Trinidad situation

since the Government herds use A.I. exclusively.

Mean calving interval for Quebec herds was 399 days,

for Trinidad herds 437 da ys and for the Government Purebred

Holstein and Crossbred herd 488 and 435 days respectively.

It was concluded that improper heat detection was

the main cause of the longer calving intervals in Trinidad

since 'the difference in calving interval between the Quebec

and Trinidad herds was 38 days (approximately two estrous

periods) and the number of services per conception was

almost identical. Within the Government herds other

additional possibilities such as improper insemination

technique, semen quality, and probable physiological abnorma­

lities may be responsible.

In the Quebec herds lactation sequence had no effect

on services per conception, however, calving interval

decreased from 405 days for lst lactation to 380 days for

4th lactation. In the Trinidad herds, however, lactàtion

sequence affected both services per conception and calving

interval. Services per conception declined from 2.5 to 1.8

and calving interval from 443 to 407 days from lst to 3rd

lactation respectively. Either of three possibilities,

173

acting singly or in combination with each other, can account

for this picture in Trinidad. Firstly, the animaIs were aIl

imported basically from Canada - a temperate region - and

were building up sorne resistance to tick-borne disease, thus

becoming progressively more adapted to a tropical environ­

ment with the passage of time. Secondly, the practice of

early culling of problem animaIs so that only those of high

fertility remained. A third, and probably the most important

factor, is the experience acquired by the farmers, both in

the earlier detection of estrus and in the general care and

management of the animaIs.

There were highly significant differences (P<:O.Ol)

between lactation sequence and services per conception and

between lactation sequence and calving interval in the

Trinidad herds. Estimated values for effects of services

per conception on calving interval showed that there was a

difference of 176 days between lst service and 4th service

in the Trinidad herds. Generally, lactation sequence

decreased as number of services increased.

In Trinidad the period of highest fertility coincided

with the peak of the rainy season, when forage growth was

more luxuriant and of a higher nutrient status than in the

dry seasone Based on a~tual calvings, it would appear that

temperature had no effect on fertility level in Trinidad.

In conclusion, the longer calving interval in the

Trinidad herds with almost identical services per conception

(~ .

174

"

as the Quebee herds, would indieate that the main problem

of infertility was improper observation o~ heat periods.

The extreme variation between aIl herds would indieate that

Many dairy ~armers eould improve the breeding e~fieieney

of their herds by eoneentrating on more e~~ieient heat

deteetion. This would also apply to the Quebee herds.

The extent to whieh low energy intake a~~eeted

fertility, partieularly in the Trinidad herds, is not elear,

sinee known requirements ~or da~ry eattle in the tropies

are not available. Further controlled studies would be

neeessary to indieate what role nutrition, or speei~ie

nutrients played in the i~ertility of these herds particu­

larly under the Trinidad conditions.

175

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( \

197

Appendix Table 1. Chemica1 Composition of Grain Mixtures fed on Quebec Farms.

On a Dry Matter Basis ~Moisture freel Farm D.M. Est. Crude Ce11u- Ca P No. TDN (%) Pro- 10se

or ENE tein ~ Mca1L4.!2.4 kg ~ ~ ~ ~

A 86.8 68 18.9 10.8 0.96 0.96 B 87.1 69 17.,3 9.9 0.55 0.86 C 80.5 72 1,3.8 8.0 0.78 0.8,3 D 84.9 71 14.8 8.6 0.,38 0.57 E 90.0 7,3 1,3.8 7.2 0.75 0.57 F 90.0 72 19.4 9.2 1.00 1.02 G 80.7 69 14.8 9.9 0.82 0.62 H 90.0 74 16.4 6.9 0.78 0.78 l 90.0 72 14.,3 8.5 0.95 1.02 J 89.1 72 15.2 8.4 0.67 0.79 K 90.0 70 1,3.8 9.5 0.56 1.11

." ...... ~.'

Appendix Table 2. Amount Fed and Chemiea1 Composition of Si1age on Quebee Farms.

On a Dry Matter Basis (moisture free) Farm Amount Fed D.M. ENE Crude Ca P

per 1000 lb (454 kg) Content Meal per Pro-eow 45.4 kg tein

lb. k~_~_ % % ~ ___ %

A 30 13.6 26.8 51 7.9 0.27 0.18 B 30 13.6 30.3 52 7.2 0.18 0.18 C 50 22.7 30.6 52 7.6 0.39 0.22 D 22 10.0 25.4 59 8.1 0.24 0.15 E 20 9.1 31.2 34 9.0 0.15 0.04 F 40 18.2 28.9 51 6.6 0.07 0.05 G 50 22.7 29.9 52 9.0 0.62 0.13 H

l 20 9.1 28.6 36 13.1 0.76 0.18 J 35 15.9 28.2 51 7.4 0.25 0011 K 45 20.5 30.9 34 4.2 0.07 0.06

1-' 'Ü (Xl

-'~'-

Appendix Table 3. Amount Fed and Chemiea1 Composition of Hays on Quebee Farms.

On a Drl Matter Basis ~moisture free) Farm Amount Fed D.M. ENE Crude Ca P

per 1000 lb (454 kg) Content Meal per Pro-eow 45.4 kg tein

lb. kg. % \

% % % 1

0'.67 A 17 7.7 93.5 36 10.7 0.17 B 17 7.7 93.2 35 10.7 0.69 0.16 C 17 7.7 91.0 45 14.4 1.29 0.1) D 16 7.3 94.9 44 12.6 1.26 0.18 E 25 Il.4 92.3 38 10.7 0.47 0.14 F Il 5.0 91.3 36 9.0 0.49 0.12 G 14 6.4 90.9 42 12.2 1.40 0.12 H 28 12.7 91.5 33 5.7 0.37 0.10 l 10 4.5 90.1 40 10.7 0.70 0.18 J 1) 5.9 89.7 34 7.1 0.42 0.12 K 15 6.8 91.0 36 10.1 0.40 0.17

".-

1-' \0 '\,()

Appendix Table 4. Average Composition of Concentrates analysed from Trinidad.

On -a~r;y: Matter Basfs (moisturefréj] Ingredient No. of D.M. Crude Ce11u- Ca P

Samp1es Content Protein 10se % % % % %

Wheat Midd1ings 1 91.9 19.4 9.4 0.17 1.21 Coconut Meal 4 94.3 24.0 17.6 0.09 0.58 Pea Hulls 2 92.3 6.8 67.2 0.50 0.13 Citrus Pu1p 1 92.8 5.9 26.1 1.71 0.09 Dairy Ration 1 3 92.9 17.8 12.1 1.36 1.18 Dairy Ration 2 4 90.8 16.8 10.4 1.36 0.78 Dairy Ration 3 4 92.1 17.3 12.3 1.17 1.04 Dairy Ration 4 1 91.9 19.1 25.7 0.73 0.63

,/

N o o

201

Appendix Table,. Estimated TDN or ENE values of eoneentrates fed to Trinidad herds as extrapolated from Figure 1 using laboratory cellulose analyses.

Cellulose Estimated TDN(%) % or ENE

(Meal per 45.4 kg)

Standard Dairy Ration (Theoretiea1 Values)

9.34 68.7

Manufaetured Rations 12.9 63.1

" " 10., 67.0

" " 12.1 64.7

" .. 12.6 63.8

" " 10.0 67.8

" " 10.6 66.8

" " 10.8 66.3

" " 12·3 64.2 " " 13.4 62.,

" " 12.9 63.2 " " Il.4 64.2

" " 9.1 69.0

202

, \_, Appendix Table 6. Average composition of Pango1a grass

(Digitaria decumbens, Stent.) found on pastures surveyed.

On a Dr~ Matter Basis ~moisture free~ Farm D.M. ENE Crude Ce11u- Ca. P No. Content Mca1 per Pro- 10se

45.4 kg tein % % % % %

1 18.7 25.1 9.6 40.0 0.40 0.43 2 Il.9 36.7 18.8 32.1 0.38 0.38

3 19.2 37.4 15.6 34.3 0.52 0.34 4 14.8 35.7 14.8 33.1 0.40 0.26

5 15.4 31.6 15.9 35.3 0.24 0.27 6 12.9 30.5 10.8 33.9. 0.20 0.22

7 21.2 30.6 9.7 33.4 0.29 0.28 8 18.5 34.9 14.9 33.8 0.23 0.28

9 14.4 31.7 7.6 31.5 0.27 0.21 10 19.7 29.1 8.2 36.0 0.30 0.24 Il 21.9 29.0 6.2 32.6 0.29 0.28 12 19.3 31.2 8.9 35.2 0.34 0.30 13 16.4 35.1 14.6 33·3 0.38 0.32 14 13.2 30.0 7.8 36.8 0.33 0.18 15 20.8 37.1 10.4 33.8 0.20 0.23 16 15.5 32.8 14.1 35.1 0.27 0.19 17 21.8 28.2 8.4 37.0 0.52 0.20 18 14.8 35.6 13.9 31.8 0.47 0.25 19 15.6 33.8 14.4 32.0 0.46 0.29 20 21.9 27.6 8.6 32.4 0.40 0.20 21 16.0 32.1 10.1 35.2 0.32 0.28 22 15.8 , . ;3.2 13.6 32 • .5 0.49 0.34 23 14.7 35.2 16.3 33·0 0.33 0.30

( ' '

\.

20.3

"- ~) Appendix Table 6 Cont'd.

On a Dry Matter Basis (moisture free) Farm D.M. ENE Crude Cel1u- Ca P No. Content Meal per Pro- lose

45.4 kg tein % % % % %

24 15.4 29.4 Il.8 .37 • .3 0.18 0 • .31 25 14.7 29.4 Il.8 .37 • .3 0 • .3.3 0 • .30 26 15.4 .31.8 14.9 .3.3.9 0.29 0 • .31 27 14.7 29.4 Il.7 .37 • .3 0 • .30 0 • .30 28 16.2 .35 • .3 1.3.0 .35 • .3 0.22 0.2.3 29 19.6 .31.2 10.8 .34.2 0.27 0 • .30 .30 11.9 .35.1 Il.5 .34.1 0 • .31 0.29 Govern- 15.6 .36.6 17 • .3 .3.3.1 0.44 0 • .35 ment Farm 20.9 .32.7 11.6 .36.5 0.25 0.21

204

Appendix Table 7. Average composition of Napier grass (Pennisitum purpurem) collected on some farms.

On a Dry Matter Basis (moisture free) Farm D.M. ENE Crude Cellu- Ca P No. Content Meal per Pro- lose

45.4 kg tein % % % % %

1 1,3.0 4,3.4 16.4 ,3,3.,3 0.52 0.26 ,3 26.8 28.4 10.2 ,36.1 0.19 0.22

10 1,3.6 ,36.7 8.,3 ,35.8 0.24 0.,31 16 14.4 ,35.,3 8.8 ,34.8 0.49 0.16 24 15.8 ,3,3.8 Il.7 ,34.4 0.26 0.45 29 17.8 ,31.7 9.4 ,34.7 0.17 0.22 Govern- Il.7 5,3.6 18.9 28.4 0.78 0.59 ment

205

Appendix Table 8. Dai1y Nutrient Requirements of Dairy Catt1e1 •

Body Weight Protein NE Crude Dig. Lactating Ca P

Cows (kg) (g) (Meal) (g) (g)

Maintenance of Mature Lactating Cows

350 468 220 6.9 14 Il

400 521 245 7.6 17 13 450 585 275 8.3 18 14 500 638 300 9.0 20 15 550 691 325 9.6 21. 16 600 734 345 10.3 22 17 650 776 365 10.9 23 18 700 830 390 Il.6 25 19 750 872 410 12.2 26 20 800 915 430 12.8 27 21

Mi1k Production (Nutrients required per kg of Mi1k)

% Fat 3.5 74 48 0.69 2.6 1.9 4.0 78 51 0.74 2.7 2.0

1 Nutrient Requirements of Dairy Catt1e Fourth revised edition, 1971 National Academy of Sciences Washington, D.C.

206

\ .... .... Appendix Table 9 • Ana1ysis of variance for services per conception (Herd effects removed).

Quebec Herds.

F. Value Source D.F. M.S. Obs 5% 1%

Herds 10 18.80 Lactation Number 3 0.33 1.16 2.76 4.13 Body Weight 1 2.30 1.17 4.00 7.08

** Yie1d 1 15.00 7.75 Protein 1 1.30 0.67 Calcium 1 0.23 0.11 Phosphorous 1 3.84 1.98 N. Energy 1 0.94 0.48 Error 70 0.20

Appendix Table 10. Ana1ysis of variance for services per conception (Herd effects removed). Trinidad Herds.

F. Value Source D.F. M.S •. Obs 5% 1%

Herds 24 ).70 Lactation Number 2 8.12 5.64** 3.00 4.61 Body Weight 1 0.52 0.)6 3.84 6.6) Yie1d. 1 0.91 0.63 Protein 1 0.80 0.54 Calcium 1 ).45 2.)9 Phosphorous 1 2.40 1.66 N. Energy 1 0.6) 0.44 Error 2)9 1.44

* (

Significant at P< .05 ** Significant at P< .01

,1

~ '1. .. /'

- . { , ..... ~

Appendix Table Il.

Source

lierds Lactation Number Body Weight Yield Protein Calcium Phosphorous N. Energy Error

Appendix Table 12.

Source

Herds Lactation Number Body Weight Yield Protein Calcium Phosphorous N. Energy

207

Analysis of variance for ca1ving interval (lierd effects removed). Quebec lierds.

F. Value D.F. M.S. Obs 2~ 1~

10 24457.1

3 5948.5 2.08 2.76 4.13 1 1152.0 0.40 /.r.00 7.08 1 3984.1 1.39

12329.8 4.32 * 1 1 4J24.4 1.51 1 301.9 0.10 1 117.5 0.04

70 2848.4

Analysis of variance for ca1ving interval (lierd effects removed). Trinidad lierds.

F. Value D.F. M.S. Obs 5% 1%

24 36718.0 2 107530.4 12.93 ** 3.00 4.61 1 28.9 0.00 3.84- 6.63 1 353.4 0.04 1 9167.3 1.10 1 1272.2 0.15 1 1412.2 0.16 1 292.3 0.03

Error 239 8315.0

* **

Significant at P < .05 Significant at P < .01