1

Module 4

Nutrition management for grazing animals

2

3

Stomachs of the Ruminant

View from rightView from right--hand sidehand side

Oesophagus

Omasum

Duodenum

Small intestineFeed

Rumen

4

The Ruminant Stomachs

AbomasumPyloricSphincter

Omasum

Reticulo-omasalorifice

Reticulum

Reticulo-ruminafold

Oesophagus

Ventral sacof Rumen

Ventral blindsac of Rumen

Dorsal blindsac of Rumen

Dorsal sac of Rumen

Duodenum

5

Ruminant Digestive System - Mouth

Saliva of ruminants does not contain enzymes to help digest the starches.It contains buffers which neutralize the fatty acid produced in the rumen.The rumen contents are maintained at approximately a pH of 6-6.5.This pH level promotes microbial growth in the rumen.Mature cows produce about 60 litres of saliva per day while sheep produce about 10 litres.

6

Functions of Saliva

The principal function of saliva is as a lubricant. The mucus in the saliva adheres to food particles and has the ability to allow easy slippage of food along the GIT.

Other roles of saliva are:Moistening of food to allow bolus formation;

Enzymatic digestion (amylase breaks starch down to dextrins and maltose);

Solubilisation of food constituents so that they can be detected by the taste buds;

Protection of the oral cavity against bacterial infection and acidic damage from food and vomitus (the high bicarbonate and phosphate content of saliva acts as a buffer); and

Slight excretory function (removal of some urea and uric acid).

7

Inside the Rumen

Anaerobic (strict and facultative anaerobes)Buffered at pH=6 (5.5-7.0)Close to isotonic (hypertonic after a meal)Constant temperature (39°C)Continuous supply of energy and nutrientsLarge volume, long turnover time for fibre digestionEnd-products removed continuously– 5 x 1010 bacteria– Mostly gram +ve on hay/forage; -ve on grains

8

Rumen Characteristics

9

Ruminant Digestion - Stomach

The stomach of the ruminant contains four compartments: the rumen, reticulum, omasum and the abomasum.The rumen or paunch is the first.The reticulum or honey comb is second.There is not a clear partition between these two compartments.The cardia, (lower part of the esophagus is common to both compartments.No enzymes are secreted in these two parts.

10

The rumen papillaeare key to VFA absorption; health is critical

The honeycomb of the reticulum is well suited forsorting particles by size and for rumination

The folds and plies of theomasum allow ingesta to betrapped and squeezed to allow dehydration prior todelivery to the abomasum

Rumen OmasumReticulum

11

Digestion in Ruminants

Breakdown of feeds in ruminants starts in the rumenDigestion is assisted by enzymes of anaerobic microbes, and plant cell enzymes– The rumen has no endogenous enzymes

12

Two Unique Characteristics of Ruminants

Ruminants tap into solar energy via digestion of cellulose– cellulose is degraded by microbes to glucose

Ruminants gain true protein from NPN by digesting the microbes in the small intestine– most rumen microbes can make true protein

from ammonia and other NPN compounds

13

Ruminants: Some Basics

Distinguishing Features

A. Fibre digestionB. Starch digestionC. Urea utilization

Microbial: specialized microbial population;bacteria, protozoa, fungi, viruses

14

Depends on:a. fibrous diet

b. microbial inoculation

c. VFA stimulation (butyrate)

Rumen Development

15

Inoculation occurs by:

1. Feed

2. Inter-animal contact (saliva)

3. Manure, soil

*inoculation does occur when animals are isolated, but much slower and less completely

Source of Rumen Microbes

16

Ruminant Nutrition

Ruminants, in contrast to non-ruminants, gain ME from fibrous roughages and by-products – they have rumen microbes that have enzymes that can degrade cellulose to glucoseRumen microbes can also synthesise all 20 common amino acids and make their proteins using ammoniaas a building monomer.They obtain energy from cellulose (microbial VFA etc) and protein (microbial protein essential amino acids)

17

Nutrient InteractionsFEEDFEED

LipidLipid CHOCHO NPNNPN ProteinProtein

RumenRumen

Body Body tissuestissues

LCFALCFA Ac/BuAc/Bu PrPr MicrobesMicrobes

Ac/BuAc/BuBB--OHBuOHBu

LCFALCFAGlucoseGlucose

Amino acidsAmino acids

LactoseLactoseGlycerolGlycerol

Milk/carcassMilk/carcassfatfat

COCO22MilkMilklactoselactose

Milk/carcassMilk/carcassproteinprotein

NADPHNADPH

NADPHNADPH

ATPATP

glycerolglycerol

18

The rumen and its microbes– bacteria– protozoa– fungi– viruses (phages)– Fermentation– Microbial growth

19

Rumen Microorganisms

Bacteria (1010 - 1011 per mL)Ciliate protozoa (105 -106 per mL)Fungi (probably less than 5% of microbial mass)Bacteriophages(temperate and lyticphages/viruses)

Most are strict anaerobes; some are facultative anaerobes

Bacteria Protozoa

20

Microbial Classifications

Strict anaerobesFacultative anaerobes

Based on substrates– Starch utilisers; fibre utilisers;

methanogens

Based on compartmentation– Fluid phase; particle attached; wall

attached

21

MicroorganismsThe three types of rumen bacteria are streptococci, lactobacilli and celluloyticbacteria.50-65% of the starch is digested in the rumen.Protein in the rumen is converted to ammonia, organic acids and amino acids.Most amino acids synthesized by the rumen, therefore, it is not necessary to supply large quantities of amino acids in the ration.

22

23

Rumen Protozoa

24

Rumen Protozoa and Fungi

Cellulose digestion occurring

25

Fungi

26

Digestibility of Grass & Legume

27

Ruminant AnimalsObtain ME from absorbed rumen VFA (Ac, Pr, Bu)Obtain ME from digested microbes flowing from the rumen to small intestineObtain essential glucose mostly by gluconeogenesis– mainly from propionate and glucogenic amino

acidsObtain essential fatty acids from dietary lipidObtain protein, minerals and vitamins from rumen microbes and undegraded dietary materials

28

Efficiency of Use of Absorbed Nutrients

Acetate and Butyrate are both sources of ATP. Both are considered to be used less efficiently (Blaxter & Armstrong 1960s). This may be an association with low digestibility feeds which require ‘gut work’ to process them.

Propionate is glucogenic and is also a source of ATP.

Glucose is usually considered to be used efficiently as a source of tissue energy deposition – but only small amounts absorbed in ruminants !

Glucose is efficiently converted to glycogen and lactose

29

VFA Transfer to Portal Blood

Acetate

Propionate

Butyrate

20

10

9

70

20

10

50

10

1

Rumen fluid

Wall Portalblood

Liver

Glucose

β-OH-But

CO2

Acetate

Glucose

β-OH-But

CO2

4β-OH-But

30

Glucose Supplies in Ruminants

Glucose is an essential nutrient in both ruminants and non-ruminants– required by CNS, red blood cells, foetus (lactose in milk)

Non-ruminants get glucose by absorbing itRuminants seldom absorb glucose as such -except when given grain diets– instead they absorb VFA from the rumen, make their own

glucose

Ruminants make their own glucose by the process of gluconeogenesis– from propionate, amino acids (lactate)

31

Glu

cone

ogen

esis

(Aer

obic

)Glucose 6-P

Pyruvate

Acetyl CoA

α-Ketoglutarate

Succinate

Oxaloacetate

Citric Acid CycleCitric Acid Cycle

e-

Glucose

GluconeogenesisGluconeogenesis

(glucogenic)

Lactose

2 x CO2

Lactate

XNot glucogenic !

32

Caution !!Take care to distinguish between:

The chemical reactions that occur in rumen microbes under ANAEROBIC conditions – Glucose 4 ATP, and

Reactions that occur AEROBICALLY in the host .

• presence of oxygen allows complete oxidation• Glucose 38 ATP

– revise biochemistry

33

Protein Supplies for Ruminants

Protein is obtained mainly from rumen microbes when digested in the abomasumand small intestineSome ruminally undegraded protein also enters the lower digestive tract for digestion (“Escape protein”,“Bypass protein”)All the essential amino acids can be made by rumen bacteria, so the host supply can be independent of the diet.

34

Feed proteins– pasture, grain, protein meals– urea and NPN

Animal proteins– examples of tissue proteins

(enzymes)– analysis of true and crude protein

content• limitations of crude protein

35

Feed ProteinsPlants provide all of the essential amino acids needed by animals – rumen bacteria > 50% C.P.

Immature herbage > 20 % crude proteinMature hays, straws - 3-6% crude proteinLegumes - Clovers, Acacia, Leucaena, LucerneCereal grains – 8-13 % crude proteinProtein meals - vegetable, animal (20-50%)

36

Sources of Protein for Ruminant Host

Microbial protein (approx. 50% of bacterial DM)– high biological value (B.V. about 80%)– nucleic acid N is about 15% of total N

Undegraded dietary protein (Escape/bypass protein; UDP)– BV depends on dietary source

Microbial protein can be derived from NPN as the solesource of N (urea)

Protein:energy ratio is important

37

Urea as a ‘Protein’ SourceUrea is a simple non-protein N (NPN) compound

NH2C=O

NH2

Urea --------------------------> CO2 + ammonia

Urea is 46% N byweight or (46 x 6.25) =

288 % crude protein

Urease

NB. Rumen microbes secrete urease, and use the resulting ammonia to build proteins.

38

Regulation of Feed Intake in Farm Animals

animal factorsphysical environment

diet quality

39

An animal’s nutrition depends on how much it eats --Also what it eats.

Its feeding behaviour determines what and how much it eats.Thus, the behaviour x nutrition interaction is a vital component of animal production!

Feeding Behaviour and NutritionDiet Selection

40

Food Intake

Whether or not an animal will meet its ME and nutrient requirements depends on what and how much it eatsFood intake may be limited by satiety but, in ruminants, the limit is usually set by gut distension or by fatigue or other factorsActual intake is usually less than potential intake and is the product of ‘relative feed availability’ (herbage mass) and ‘relative feed ingestibility’ (feed digestibility).

41

POTENTIAL INTAKE RELATIVE INTAKE

INTAKE = OF FOOD BY THE X OFFERED BY THE

ANIMAL PASTURE

Mature size Ease of harvesting

Relative size (relative availability)

Relative condition Rate of breakdown

Stage of lactation (relative ingestibility)

Example:

Intake = 1.6 kg DM X 0.75

= 1.2 kg DM

Prediction of Intake from Pasture

42

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.0 0.2 0.4 0.6 0.8 1.0

Relative size

Pote

ntia

l int

ake

(kg

DM

)

Above average condition

Potential Intake of Food by SheepMature Weight 50kg (Red) or 40kg (Blue)

43

0.00.10.20.30.40.50.60.70.80.91.01.11.2

30 40 50 60 70 80

Dry matter digestibility (%)

Rela

tive

inge

stib

ility

TropicalTemperateLegume

Relative Ingestibility of Tropical and Temperate Grasses and Legumes

44

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 500 1000 1500 2000 2500

Weight of herbage DM (kg/ha)

Rel

ativ

e va

lue

RRRTRA

Relative Availability (RA) and its Components, Relative Rate of Eating (RR) and Relative Time

Spent Grazing (RT)

0.00.10.20.30.40.50.60.70.80.91.0

0 500 1000 1500 2000

Weight of herbage (kg DM/ha)

Rela

tive

avai

labi

lity

TallerShorter

Relative Availability of Herbage for Sheep, as Affected by Weight and Height

46

0.00.20.40.60.81.01.21.41.61.8

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Herbage weight (tonnes DM/ha)

Feed

inta

ke (k

g D

M)

Feed Intake by Sheep of Mature Weight 50kg, for Different Herbage Weights and

Mean DMD

47

Diet Digestibility for Different Herbage Weights Compared with Mean DM

Digestibility of Herbage

40

45

50

55

60

65

70

75

80

85

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Herbage weight (tonnes DM/ha)

Mea

n di

et d

iges

tibili

ty (%

)Mean DMDof herbage

75

65

55

45

48

Motivation (Driving Force) for Feeding Activity

Driving force for feeding is:– short-term -- survival– longer-term -- successful growth leading to reproduction

(rearing of offspring)Animals have evolved with a ‘genetic blueprint’ that defines a growth pattern consistent with optimal survival and reproduction. Behaviour drives aim to fulfill genetic potential as nearly as possible.‘Drives’, generated by the ‘eating centre’ in the hypothalamus, lead to behaviours used by animals to search for, locate and ingest foods.

49

Larger animals have smaller surface areas per unit live weight, so generally have lower energy requirements and metabolic rate per unit live weight. Thus maintenance energy requirements are a power function of live weight (e.g. W0.75)Of course, requirements still increase as animals become heavier (but the increase is not linear) . Across all species: – Maint. Energy Requirement = 300 kJ/ W0.75 per day

• Sheep 234 kJ/W0.75 Cattle 300 kJ/ W0.75 Pigs 226 kJ/ W0.75

• Birds 305 kJ/ W0.75

ME requirements for maintenance are about 100/70* of the above (km=0.7). Additional energy requirements are incurred for growth of carcass and conceptus and for milk production (energy content/ Kg or Kf)

*450

Animals Eat to Meet Energy and Nutrient Requirements

50

Animals Eat to Meet Energy and Nutrient Requirements

As well as having energy requirements for (basal) maintenance, animals also use energy for:– ingestion and digestion of food (peristalsis, rumination,

production of enzymes, active (re)absorption, repair of gut wall damage)

– for walking, climbing, shivering, panting etc In ruminants especially, the costs of ingesting and digesting fibrous feeds may be relatively highAll the above are traditionally considered to represent ‘inefficiency’ in net energy use - they reduce the efficiency of utilization of energy for growth or production (kg or kp ) - they could equally be considered additional ‘maintenance’ costs

51

Animals Eat to Meet Energy & Nutrient Requirements

If a diet is balanced, animals respond to its dilution with indigestible materials by eating more (if they have the capacity to do so).

Once ‘capacity is reached’, dilution of the diet results in reductions in energy and nutrient intake, e.g. broiler chicks < 11 MJ/kg.

Energy Feed Energydensity intake intakeMJ/kg (g/d) (MJ/day)

12.0 127 1.5212.8 118 1.5113.6 112 1.5214.5 106 1.53

Leeson and Summers (1991)

52

Potential/Actual Intake

Potential intake is the amount of feed an animal will ingest under ideal conditions, i.e. it is genetically determined by– animal size and metabolic rate, gut capacity,

food preferences, potential for growth and production etc

Actual (voluntary) intake is usually less than potential, constrained by– feed quality and quantity– animal behaviour and feedback mechanisms

53

Pasture Constraints to Intake

54

Pasture Availability

55

Ruminants - Pasture Availability

Intake is restricted by low pasture availability (< 1,500 kg/ha)low sward density orlow sward height, leading toSmall mouthfuls and fatigue

56

Animal’s Choice of Diet - SensesDepends on reflexes of attention, approach, examinationDepends on senses of:– sight (not used much by sheep)

– touch– odour (chemical stimulii; integrated by brain and CNS)

– taste (preferences change if senses removed)Food characteristics stimulate the animal senses. The effects can be *associated with metabolic *consequences, and the animal *learns about individual foods and *memorizes this. * key words

57

Stimulus to Eat

Integrated signals dependent on energy and nutrient (amino acid) status, e.g.

• low rate of glucose oxidation in liver• low rate of fatty acid oxidation

are conveyed to the brain (hypothalamus) by the autonomic nervous system (vagus)

Hypothalamus initiates feeding activity

58

Con

trol o

f fee

d in

take

Feed intake

Stimulatoryfactors

Inhibitory factors

Signals to theCNS

(Neural and hormonalsignals)

Based on McClymont (1967)

BalanceBalance

Protein demandEnergy demand (physiological state)

- climateNutrient demand (amino acids, Ca)Low gut fillLow blood glucose or VFAFamiliar flavour of feed

Over-supply of energy- high blood glucose- high rumen VFA

Over-supply of proteinNutrient imbalance, toxinsGut distension, gut CCK, osmolalityFatigue (time to graze sparse plants)Disease, parasitism, high body temperatureUnfamiliar feed (neophobia)

59

At the Start of a MealAnimals face a challenge (what to select?)

Familiar?Familiar?

60

Neophobia = Fear of ‘New’

Fear or apprehension related to novel items– unfamiliar foods,

feeders, people, situations

Thus, unfamiliarfoods are treated with caution– sound evolutionary

basis

61

Learning About New Foods

Attentive, inquisitive but neophobiaSocial - observational learning

• red squirrels learn to open hickory nuts• oyster-catchers learn one of 2 different ways

to open mussels• sheep learn about wheat, grass from

mother/others– by watching, or by detecting cues in milk

Personal- ‘trial and error’ learning• conditioned taste aversion (toxicity, illness)

62

Social LearningAnimals learn by observation/mimicking– sensitive learning period about weaning time

63

Social Learning - Familiar vs Novel FoodIntake of wheat by adult sheep which previously ate wheat (familiar) and by sheep that had no experience of wheat

12

34

No experience

Familiar

050

100150

200250

300

350

400In

take

of w

heat

(g/h

ead

per d

ay)

Weeks on feed

knowledge of foods is subject to knowledge of foods is subject to long memorylong memory

64

Acceptance of New Feed, Rice Bran, by Sheep (Unfamiliar Cues)

0

5

10

15

20

25

30

35

40

45

50

0 3 6 9 12 15 18 21

Days of learning

Bra

n in

take

/5 m

in

Control Grass odour Grass flavour Faecal odour

DogDogsmellsmell

+ flavour+ flavour

controlcontrol+ odour+ odour

65

“Trial and Error’ - Conditioned Response Learning

Investigatory reflex taste foodUnconditioned stimulus response

• food (taste salivation)

Learned association - food/bellConditioned stimulus (bell salivation)

Pavlov:

66

Conditioned Aversion

Avoidance of (or preference for) specific foods is conditioned by the after-effects of ingestion (e.g. LiCl-induced malaise leads to avoidance)The malaise (detected via gut, liver, brain, other afferent receptors) becomes associated with specific identifiers for the food (taste, odour, colour, texture) Animal becomes averse to food cues.

67

Conditioned Aversion (2)The malaise caused by the toxicant LiCl operates via the emetic (vomiting) centreemetic centre stimulation is a post-ingestive consequence which generates a learned associationwith food/malaiseUNE - association between the feed identifiers and the anti-emetic drugs attenuated the food aversions caused by LiCl administered immediately after sheep ate oats, wheat or sorghum

UNE - food aversion conditioned in anaesthesisedsheep

• association is partly non-cognitive (probably also humans)

68

Conditioned Aversion (3)

Associations can be made with considerable delays between ingestion and consequences– increasing delay, decreasing strength of association

(Provenza, Nolan & Lynch, 1993)

Strength of aversion is• increased by neophobia • dose-dependent with toxins

Degree of malaise may depend on the efficiency of metabolic detoxification– probably malaise is balanced against positive stimuli

from food benefits. LiCl 40 mgLi/kgW

69

Development/Extinguishment of Food Aversion to Familiar Food

0

50

100

150

200

23-Mar

24-Mar25-Mar

26-Mar29-Mar

30-Mar31-Mar

5-Apr19-Apr

Intake (bites/2 m in)

Li group

NaCl

LiCl induced aversion to a familiar food (lucerne) in sheepExtinguishment of the lucerne aversion

ExtinguishmentExtinguishment

Total aversionTotal aversionLiClLiCl

70

Learned Food Preferences ???

Learned preferences may develop for foods leading to positive outcomes (rather than aversion to negatives)

Dual control - preference/avoidance• more powerful control system

71

“Nutritional Wisdom” (Euphagia)

Learned aversion (preference) model– rats quickly discover harmful or beneficial effects of

novel foods (within 12 hours). Intake of ‘beneficial’feeds increases.

– poultry learn to ‘choice feed’ appropriately, varying choice to provide for their current needs (e.g. layers and Ca intake)

– ruminants appear to choose to obtain appropriate amounts of Na, N, Co, S but not P. They avoid tanniniferous/alkaloid/ oxalate-containing plants

72

Food Checklist

Familiar,– known unsafe avoid– safe, not needed

avoid– safe & nutritious eat

Unfamiliar, potentially unsafe

test cautiously

Familiar?Familiar?

73

Choice Feeding in Layers

Complete diet consists of a mix of– grain– concentrate (protein,

mins & vits)– calcium source

Choice-fed - the above ingredients in 3 separate bins in front of each bird

74

Production in Choice-Fed Layers

Diet MEIntake(MJ/d)

ProteinIntake(g/d)

CaIntake(g/d)

EggMass(g/d)

Convent-ional 1.28 18.0 5.6 57

Choice-fed 1.35 21.0 4.2 62

Choice fed consumed more ME, more protein, but less calcium and produced more egg mass.This was from the same number (93%) of larger eggs.

75

Eating for Energy? – There’s More!

‘Animals eat for energy’– the diet is assumed to be ‘balanced’ and food

intake is a response to energy requirement

Emmans (1981) restated the above adage– ‘Animals eat for the most limiting feed

component’• implies that animals can direct feeding

behaviour in response to signals dependent on internal nutrient status or imbalances.

76

Microbial Energy/Nutrient Requirements

Energy Substrates (cellulose, hemi-cellulose, pectin, sugars etc)Energy conserved as ATPNitrogen source (ammonia*, peptides)Minerals (S, Co, P)Vitamins (provided by cross-feeding)Water

* most bacterial spp can grow with ammonia as thesole source of nitrogen; protozoa require amino acids

77

Gas space

Raft

78

Mic

robi

al fe

rmen

tatio

nan

d gr

owth

Digestible Organic Matter

Carbon intermediates

Microbialpolymers(Acetate, Propionate

Butyrate)

ATPATP

Glycolysis

CO2Methane

NH3

S2-

FERMENTATION GROWTH

VFAsMaintenance

GlucoseMicrobe

ADP

Rumen fluid

NH3Na, K, P, etc

S2-

CCHH

OO

79

Fermentation/Microbial Energy

Organic matter is fermented by microbes to obtain building materials and ATP– CHO - starches, cellulose, hemi-cellulose,

pectin, sugars, fructans, pentosans– protein, peptides and amino acids– lipids, long chain fatty acids and VFA• Ash (minerals) is also used, but does

not provide energy

OM

Glucose

Pyruvate

Ac Pr Bu

ATPATPNADHH

80

Growth of Microbes Used to describe increase in biomass and consequent ‘doubling’

Involves bacterial, protozoal, fungal synthesis of:– proteins (all ‘essential’ amino acids)– lipids (cell membranes etc)– nucleic acids (DNA, RNA)– storage polysaccharides

Growth may be restricted if any one factor is not present in sufficient quantities - Concept of major limiting factor

FERMENTATION

Organic Matter

Carbon intermediates

Microbial cells

ATP

Glycolysis

CO2Methane

(e.g. pyruvate,oxaloacetate)

NHminerals

3

GROWTH

VFAs

81

Growth of Microbes (2)

1 kg of fermentable OM – 19 MJ of ME (assuming OM is hexose)– generates about 24 mol ATP– grows about 240 g cell DM (YATP = 10)– containing about 120 g true protein (50% protein)– equiv. about 19 g nitrogen (CP/6.25)

19 g N /kg fermentable OM– 12 % CP in OM; 1 g N/MJ of ME – (Minimum N requirement if digest’y = 100%)

82

Energy Requirement for Microbial Growth

• ATP is required by cells for

•Maintenance

•Chemical bond formation–Energy is stored in C-C, C-H, N-C and N-H bonds

–1 mol ATP can create about 10-15 g cell DM

–Yield depends on cell composition

83

ATP Availability for Polymer Synthesis is Reduced by Maintenance ATP

ATP from fermentation is used for:– polymer synthesis

• (protein, lipid, etc)

– cell maintenance • (50 mmol ATP/g cells/min)

Thus actual yield of cells /mol ATP (YATP) is less than theoretical (usually 10-14)maintenance uses up half of the available ATP (depending on residence time)

FERMENTATION

Organic Matter

Carbon intermediates

Microbial cells

ATP

Glycolysis

CO2Methane

(e.g. pyruvate,oxaloacetate)

NHminerals

3

GROWTH

VFAs

84

Microbial Fermentation and Growth

Fermentation

Organic Matter

Carbon intermediates

Microbial biomass

ATP

Glycolysis

CO2Methane

NHminerals

3

GrowthVFAs

YYATPATP refers to yield of cell DMper mole ATP available

85

Microbial Fermentation and GrowthOrganic Matter

Fermentation

Carbon intermediates

Microbial cells(polymers)(Acetate, Propionate, Butyrate)

ATP

Glycolysis

CO2Methane

(e.g. pyruvate,oxaloacetate)

NHminerals

3

GrowthVFAs

Fermentation and growth are said to be ‘coupled’ via ATPFermentation generates reducing equivalents - NADH

NADHH

86

Effect of type of diet on VFA proportions

0

20

40

60

80

Acetate Propionate Butyrate

% o

f tot

al V

FARoughage

Concentrate

Concentrates are more rapidly fermented. Rate of production of NADH isfaster, NADH and H2 concentrations increase, inhibiting acetate formationand ‘forcing’ propionate production.

87

Theoretical ATP for Synthesis 1 kg CellsCellcomponents

Composition(g/kg DM)

Composition(g/kg OM)

ATP used(mol/kgcomponent)

ATP used(mol/ kg cellOM)

Protein 320 370 42 15.4Nucleic acids 80 92 18 1.6Lipid 110 126 52 6.6P’saccharide 170 195 12 2.3Cell wall 90 103 14 1.7Small molecules 100 115 10 1.1Ash 130 - 0 0

Total 1000 1000 28.7Adapted from Czerkawski (1986) Theoretically, approx. 30 g cell DM/mol ATPTheoretically, approx. 30 g cell DM/mol ATP

88

Yield of Cells Depends on Cell Composition

Empirical formula of microbial cells[C6H10.2O2.47N0.91S0.015] MW= 135– this indicates cells are reduced, cf. glucose (H2

used)

– this also indicates the amounts of N and S incorporated per 1 kg cells produced, i.e.

N = (14*0.91)/135 = 9.4%N or 59% crude protein S = (32*.015)/135 = 0.4 %S ~ N:S ratio = 23.

89

Temperature

0

5

10

15

20

25

30

35

40

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Deg

rees

Cel

cius

Mean max tempMean min temp

90

Relative Humidity – Barkly Tableland

0

10

20

30

40

50

60

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

% R

H

91

Rainfall

0

20

40

60

80

100

120

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

mm

0

1

2

3

4

5

6

7

8

daysRainfall

Rain days

92

MITCHELL GRASS PROTEIN LEVELS

0.002.00

4.006.008.00

10.0012.00

Mar-98

Jun-98

Sep-98Dec-9

8Mar-9

9Ju

n-99Sep-99Dec-9

9Apr-0

0Ju

l-00

Oct-00

Mar-01

Jun-01

93

Pastures are Deficient in Many Nutrients for Most of the Year (Leng 2003)

Nutrients

-14001Carbohydrate-7005Protein

+1000.2Sodium-201.4Magnesium -701.2Phosphorus+58.7Calcium

% of animal requirement

g/kg DM(dry pasture)

Mineral

94

Nutritional Characteristics of Tropical Regions

1. Breeding operations dominate the industry

2. Dry season – pastures deficient in energy, protein and phosphorus (Vit A?)

3. Wet season – phosphorus most limiting nutrient

95

‘Bone Chewing’

96

Principles of Supplementary Feeding in Grazing Systems

Grazing animals often need supplements when nutrient supply from grazing is inadequate

Supplements are costly, but the response to supplements can be erratic

The lecture examines the biology of supplementary feeding, the better to predict when and why supplement response occurs

97

Schematic Description of Major Reasons for Supplementary Feeding

in Grazing Systems

Supplement

Reason for feeding Example Effect on intake of diet

Negate effects of a Polyethylene glycol to Usually increasedsubstance in diet overcome tannin effects

Overcome a frank Deficiency of vitamin, deficiency mineral, rumen-degradable N (complementation)

Intake increased

Contribute to energy, Increase ME and/or increase Intake decreased to variable protein supplies amino acid supply as extent (substitution).

either microbial protein,UDP or both

98

Interactions Between Herbage and Supplement Intakes

Supplementation: Supplement eaten, herbage intake stays the same – a rare event!Substitution: Supplement eaten, herbage intake reduced – the usual situationComplementation: Supplement eaten, herbage intake increased – occurs when supplement provides nutrient which was limiting intake (e.g. rumen-degradable N)

99

Factors Influencing Substitution

Substitution usually worse if:More pasture availableMore supplement fedPasture quality highSupplement quality highDemand for nutrients lower (e.g. maintenance cf. lactation)Supplement fed infrequently

100

Substitution and Total Intake

Unless substitution is >100%:

Supplementation still increases total intake

Animal performance better because supplement

quality usually higher than rest of diet

101

Supplementary Feeding and Wool Growth

Wool growth usually limited by protein supply (and

sulphur-amino acid supply within that)

Upper limit of response to protein depends on energy

intake

Economic responses of wool growth to minerals,

vitamins are unlikely

102

Supplementary Feeding and Reproduction

Nutrient requirements for ovulation very small, but short-

term supplementation can increase ovulation rate

(flushing)

In early pregnancy, high feeding levels can compromise

embryo survival

Severe under-nutrition during mid- or late-pregnancy can

reduce milk production in subsequent lactation

103

Behavioural Aspects of Supplementary Feeding

Introduce grain supplements gradually

Problem of ‘shy feeders’ helped by infrequent feeding

Early exposure to supplements helps with acceptance of

future supplements

Supplementation in presence of ‘experienced’ animals

increases acceptance rate and intake

104

Other Aspects of Supplementary Feeding

Know how much herbage is there!

Don’t leave it too late! Allow for time needed to accept

supplement

Make sure intestinal parasites are under control!

Computer packages can aid decision making

105

Methods of Supplement Delivery

1. Loose licks2. Roller drums3. Blocks4. Water medication

106

107

Effects of Supplementation (NT) (Winter and Adamu 2002)

198Salt + urea + phosphorus + CSM (400g/d)

188Salt + urea + phosphorus

145Salt + phosphorus (10g/d)

91Salt + urea (50g/d)

68Salt

Annual weight gain (kg)

Supplementation

108

Using Molasses and Urea (Leng 2003)

750Urea 2% + 500g CSM

1200Urea 3% + 200g CSM + 1kg WCS

380Urea 3%

0Urea 1%

-120Nil

Growth (g/d)Supplements provided with molasses

109

Supplementing in the Last Trimester of Pregnancy (Lindsay and Loxton 1981)

32+45486Urea/Sulphur/CSM

31-19372Urea/Sulphur

22-47252Nil

Calf birth wt (kg)

Wt change (kg/60d)

Forage intake

(kg/60d)

Supplement

110

Effect of Supplement on Reproduction (Sullivan et al. 1997)

15094Kg calf weaned per 400kg cow mated

405355Cow wt (kg)

190150Weaning wt (kg)

8055Weaning %

Supplement(Urea in dry/P in wet)

Nil supplement

111

Nice theory, but how does this relate to practical nutritional management of a

breeding herd?

Two key questions:1. What is the aim of supplementation?2. When do we supplement?

112

“Weaning is the best form of supplementation!”

4776Pregnancy rate (%)

452518Cow wt (kg)

Normal weaning

Radical weaning

113

Average Breeder Condition Score (+/- SE) per Muster

4

5

6

7

Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02

CO

ND

ITIO

N S

CO

RE

114

Weight (+/- SE) for Average Weight at each Pregnancy/Lactation Status

300

350

400

450

500

550

600

Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02

WEI

GH

T (k

g)

Not Pregnant / DRYNot Pregnant / WETPregnant / DRYPregnant / WET

115

75

77

79

81

83

85

87

89

91

93

95

4 5 6 7 8&9BCS

preg

nanc

y ra

te (%

)

5.4

5.6

5.8

6

6.2

6.4

6.6

6.8

preg

nanc

y di

agno

sis

(mon

th)

%

month (PD)

116

700

750

800

850

900

950

4 5 6 7 8&9BCS

calf

grow

th (g

/d)

165

170

175

180

185

190

195

200

205

210

wea

ning

wei

ght (

kg)

g/d

kg

117

75

77

79

81

83

85

87

89

91

93

95

4 5 6 7 8&9BCS

preg

nanc

y ra

te (%

)

750

770

790

810

830

850

870

890

910

930

950

calf

grow

th (g

/d)

%

g/d

118

Efficiency of Production

Efficiency of feed utilization– FCE or FCR – food energy for maintenance and production– growth promotants, (β agonists), antibiotics

Rumen efficiency (microbes)– YATP, defaunation, rumen modifiers (monensin)

Efficiency of the whole herd or flock– cost of breeders, non-breeders– cost efficiency depends on market prices

119

Efficiency of Animal Production

– Individual animal basis

– Food Conversion Efficiency

Weight gain (kg)/Food intake (kg)

or its inverse

Food Conversion Ratio

120

Food Conversion Efficiency

FCR = food consumed for product produced– digestibility, efficiency of use of absorbed nutrients,

maintenance energy requirementThis can be thought of as– per animal (low FCE)– per herd or flock

• in a herd of cattle, the breeders and bulls may use more than 70% of the feed needed to produce each kg of meat

• long inter-calving intervals, low conception rates, low milk production and low calf growth rates, late puberty

121

Energy Budgets

Although the energy in the gain at any stage of growth is lower in a food-restricted animal, the animal takes longerto reach a given weight.Maintenance energy is therefore required over a longer period

Cumulative ME* in broilers grown toCumulative ME* in broilers grown to1.5 kg on 1.5 kg on ad libad lib or or restrictedrestricted feedingfeeding

* * sum of maintenance ME + sum of maintenance ME + ME for gainME for gain

0

20

40

60

80

0 0.5 1 1.5

Liveweight (kg)

Cum

ulat

ive

ME

inta

ke

(MJ)

ad lib restricted

ad lib

restricted

122

FCR Decreases with Intake

8

10

12

14

16

7 9 11 13

Feed intake (kg DM/d)

FCR

123

Rumen

Rumen fermentation and growth– g cell DM/ mol OM fermented– G cell DM/ mol ATP from fermentation

• Affected by presence or absence of protozoa• Presence of bacteriophages (viruses)• Dilution rate

Protein:energy ratio in end-products– Affects efficiency of gain, milk production

124

Rumen Modifiers

Best known is ‘Rumensin’/monensin– Discovered during feeding chicken litter

Virginiomycin used to inhibit S. bovis– Antibiotic – limited use in the future

Exogenous enzymes for ruminants to assist microbial digestion

125

Defaunation - Protozoa-Free Rumen

Protozoa live in the rumen and utilise energy and nutrients for growthThey tend to remain in the rumen, avoiding washout to the lower gutThey compete with bacteria for resources and space, and reduce the number of bacteria/ml– thus less bacteria (and less protein etc) leaves the

rumen– energy is released as heat due to the presence of

non-productive protozoa

Feed Additives

Medicants for disease, parasite controlBiologically active substances

• anti-fungal agents• antibiotics (to inhibit undesirable gut flora; note ‘resistance’)• probiotics (beneficial live organisms or spores)• coccidiostats (Monensin and Lasalosid inhibit Eimeria spp.)• exogenous enzymes, e.g. degrade NSPs• buffers (especially for grain-fed stock)• yolk pigments for layers• chelating agents/odour eaters (bind ammonia)• antioxidants in feeds for storage

Pelletting aids (binding agents - fats, oils, bentonite)Flavour enhancers (doubtful effectiveness)

127

Tissue Growth Efficiency

Genetic factors Efficiency affected by digestibility of diet– Affects use of energy by gut and liver– Alters ratio of acetate:propionate

Climate (temperature and humidity)Disease (lower voluntary intake)Prior nutritionPresent growth or production level

128

The End