Ovinge Lauren Thesis - ttu-ir.tdl.org
Transcript of Ovinge Lauren Thesis - ttu-ir.tdl.org
The use of alternative feeding strategies to improve feedlot beef cattle growth performance and nutrient utilization
by
Lauren A. Ovinge, B.S.
A Thesis
In
Animal Science
Submitted to the Graduate Faculty Of Texas Tech University in
Partial Fulfillment of the Requirements for
the Degree of
MASTER OF SCIENCES
Approved
Jhones O. Sarturi Chair of Committee
Michael A. Ballou
Sara J. Trojan
Mark A. Sheridan Dean of the Graduate School
August, 2016
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ACKNOWLEDGEMENTS
Firstand foremost Iwould like to thankmyparents forsupporting
methroughthisjourneyandprovidingmewithtwogreatexamplesinwhich
to follow. Your support, love and encouragement have been greatly
appreciatedthroughoutmyuniversitycareer. Iwouldalso liketothankmy
threebrothersandmyboyfriend;yourconversationswerealwaysawelcome
distraction. Secondly, the success you have all enjoyed in your respective
fieldsthroughhardworkanddedicationhashelpedtogivememotivationto
succeedinmine.
IwouldalsoliketothankDr.JhonesSarturiforspendingthelasttwo
years working with and mentoring me. Your knowledge and wisdom has
helpedmeturnfromsomeonewithaninterest infeedlotnutritionintoone
withapassionforfeedlotnutrition.Youhavegivenmeasolidfoundationon
whichtobuildmyfuturecareeraswellashowtolivemylife.
Iwould also like to thank the othermembers onmy committee,Dr.
Trojanfortakingthetimetowritemereferencelettersandaboutthefeedlot
industry, and Dr. Ballou for taking the time to involve us and teach us
statistics. I would also like to thank the students here at Texas Tech,
specifically those in our lab group that helpedme through experiments no
matterwhatwasgoingon.ThesupportfromPedroCampanili,LucasPellarin,
andBarbaraLemosespeciallyhelpedmegetthroughthis.Finally,theother
friendsI’vemadehereaswellasthosebackinCanadaisgreatlyappreciated,
yourinsightsintobeefproductionhavehelpedmetogrowandlearn.
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS.............................................................................................ii
ABSTRACT....................................................................................................................vi
LISTOFTABLES..........................................................................................................ix
LISTOFFIGURES........................................................................................................xi
I.LITERATUREREVIEW.............................................................................................1NaturalProgramBeefSteerProductionMethods...................................................1
Introduction.........................................................................................................................1
ConventionalandNonconventionalBeefProduction............................................3
Direct-FedMicrobials........................................................................................................4
Probiotics......................................................................................................................................6Yeast................................................................................................................................................6
MechanismsofAction.......................................................................................................7
LacticAcidUtilization..............................................................................................................9FiberDigestibility....................................................................................................................10AmmoniaUptake......................................................................................................................11
Supplementation..............................................................................................................12
Levels............................................................................................................................................12Activity..........................................................................................................................................13DietDigestibility.......................................................................................................................14Health............................................................................................................................................15GrowthPerformance..............................................................................................................17CarcassCharacteristics..........................................................................................................18Cost.................................................................................................................................................19Implications................................................................................................................................20
Conclusions.........................................................................................................................20
AdaptationofBeefFinishingSteerstoHighConcentrateFinishingDiets....23
Introduction.......................................................................................................................23
AdaptationPeriod............................................................................................................25
Methods........................................................................................................................................27Ingredients,TimeandSorting............................................................................................28
Health...................................................................................................................................30
Acidosis........................................................................................................................................30Bloat...............................................................................................................................................31
GrowthPerformanceandFeedIntake......................................................................33
RuminalBacterialCommunity.....................................................................................34
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CottonBurrs.......................................................................................................................36
Implications........................................................................................................................38
II.Effectofaliveyeastproductinafinishingfeedlotdietongrowth
performance,digestibility,andcarcasscharacteristicsinnatural
programfeedlotsteers...........................................................................................40Abstract................................................................................................................................40
Introduction.......................................................................................................................42
MaterialsandMethods...................................................................................................43
FeedlotGrowthPerformance...................................................................................................43ApparentTotalTractNutrientDigestibility......................................................................46LaboratorialAnalyses.................................................................................................................47FeedingBehavior..........................................................................................................................47StatisticalAnalyses.......................................................................................................................48
Results..................................................................................................................................48
TreatmentData..............................................................................................................................48GrowthPerformanceandCarcassCharacteristics.........................................................49ApparentTotalTractNutrientDigestibility......................................................................50
Discussion...........................................................................................................................51
Implications........................................................................................................................57
TablesandFigures...........................................................................................................59
III.CottonBurrsasanalternativeroughagesourcetoadaptbeefsteers
tosteam-flakedcornbasedfinisherdiets.......................................................67Abstract................................................................................................................................67
Introduction.......................................................................................................................69
MaterialsandMethods...................................................................................................70
Treatments,ExperimentalDesignandFeeding...............................................................70RuminalpH,VolatileFattyAcids,andAmmonia.............................................................71ApparentTotalTractNutrientDigestibility......................................................................72LabAnalyses....................................................................................................................................72RuminalInSituWheatHayDegradability..........................................................................73FeedingBehavior..........................................................................................................................74StatisticalAnalyses.......................................................................................................................75
Results..................................................................................................................................75
DryMatterIntake..........................................................................................................................75RuminalpH,VolatileFattyAcids,andAmmonia.............................................................76ApparentTotalTractNutrientDigestibility......................................................................78RuminalInSituWheatHayDegradability..........................................................................79FeedingBehavior..........................................................................................................................79
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Discussion...........................................................................................................................80
Implications........................................................................................................................87
LiteratureCited.................................................................................................................89
TablesandFigures...........................................................................................................98
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ABSTRACT
The use of alternative feeding strategies such as yeast as a feed additive
and cotton burrs as a roughage source to improve feedlot beef cattle growth
performance and nutrient utilization were evaluated in two experiments. The first
experiment evaluated the effects of live yeast fed to natural program beef steers
and its effect on growth performance, apparent total tract nutrient digestibility,
carcass characteristics, and feeding behavior. In experiment 1, steers (n = 144;
341 ± 52 kg) were assigned to 1 of 3 treatments, Control (CTL), Low Yeast (LY),
and High Yeast (HY) in a completely randomized block design (12
pens/treatment). Data were analyzed using the GLIMMIX procedure of SAS, with
pen as experimental unit. Gain efficiency tended to be quadratically improved (P
= 0.08) between d0 and 183 with LY diet being 4.3% greater than other
treatments. The number of premium choice carcasses increased linearly (P < 0.01)
with increasing yeast levels at 33.3%, 68.8% and 70%, respectively. There was a
tendency (P = 0.09) for choice carcasses to be decreased linearly with increasing
yeast level. A quadratic response was observed for nutrient digestibility, in which
steers fed LY had improved digestibility (P < 0.01) of dry matter by 5.4%,
organic matter by 4.8%, neutral detergent fiber by 15.2%, acid detergent fiber by
20.2%, crude protein by 6.2%, and ether extract by 2.5% compared to HY and
CTL treatments. Moderate inclusion of live yeast improved efficiency of nutrient
utilization of steers fed steam-flaked corn-based finishing diets, which tended to
positively affect growth performance.
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The second study evaluated the effect of cotton burrs as a roughage source
during the transition of beef cattle (hay to finisher diet) on intake, ruminal
characteristics, apparent total tract nutrient digestibility, and feeding behavior.
Ruminally cannulated steers (n = 6; BW = 235 ± 81 kg) were assigned using a
complete randomized design to 1 of 2 adaptation strategies: alfalfa hay or cotton
burrs-based. Steers were fed ad libitum once daily, a series of six diets (7-d period
each): wheat hay; 4 step-ups; and a finisher. Ruminal fiber degradability, pH,
VFA and NH3, and apparent total tract nutrient digestibility were measured. Data
were analyzed using GLIMMIX procedure of SAS (wheat hay period used as
covariate). Intake was not affected by adaptation strategies (P ≥ 0.16), except for
a tendency (P = 0.10) for alfalfa-strategy steers to ruminate more per kg of NDF
consumed during finisher diet. Steers fed cotton burrs-strategy had a lower
ruminal pH average on step-3 and finisher periods (5.62 and 5.51 vs. 6.04 and
5.83; P < 0.01 and P = 0.05, respectively). A greater area of pH below 5.6 (200
vs. 15 min*pH; P < 0.01); lower ruminal NH3 concentration (5.1 vs. 8.8 mg/L; P
< 0.01); and lower digestibility (OM, ADF, and hemicellulose; P = 0.02) during
step-3 were also observed for steers fed cotton burrs-strategy versus alfalfa hay
strategy, respectively. However, cotton burrs-strategy steers showed greater (P <
0.01) NDF digestibility during step-4; greater (P < 0.01) OM digestibility during
finisher diet; and lower acetate/propionate ratio (P = 0.04) with a tendency (P =
0.08) to have greater propionate molar proportion during step-2. Ruminal fiber
degradability was not affected by adaptation strategies (P ≥ 0.36). Cotton burrs
adaptation strategy induced an improved ruminal fermentation environment
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during finisher diet, although with riskier ruminal pH and rumination than alfalfa-
strategy. Beef cattle diets can include a variety of products to effect growth
performance and nutrient utilization, which provides a benefit to beef cattle
producers.
Key words: adaptation, beef cattle, alternative feeds, cotton, yeast
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LIST OF TABLES
1. Dietaryingredientsandnutritionalcompositionofdietsfedtonaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.................................................................................................................59
2. EffectsofABVistayeast(Saccharomycescerevisiae)ongrowthperformanceofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.........................................................................................60
3. EffectsofABVistayeast(Saccharomycescerevisiae)oncarcasscharacteristicsofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.........................................................................................61
4. EffectsofABVistayeast(Saccharomycescerevisiae)oncarcassqualityofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.........................................................................................62
5. EffectsofABVistayeast(Saccharomycescerevisiae)onliverscoresofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.........................................................................................63
6. EffectsofABVistayeast(Saccharomycescerevisiae)onfeedingbehaviorofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.........................................................................................64
7. Dietarycompositionofadaptationdietsusingcottonburrsoralfalfahayasaroughagesource.........................................................................98
8. Analyzednutritionalcompositionofadaptationdietsusingcottonburrsoralfalfahayasaroughagesource..........................................99
9. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsondrymatterintake,ruminalparameters-WheatHay,Step1and2................................................................................................................100
10. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsondrymatterintake,ruminalparameters-Steps3and4,Finisher........................................................................................................................101
11. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonruminalvolatilefattyacidprofile-WheatHay,Step1and2..........102
12. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonruminalvolatilefattyacidprofile-Step3,4andFinisher................103
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13. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonapparenttotaltractnutrientdigestibility-WheatHay,Step1and2................................................................................................................104
14. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonapparenttotaltractnutrientdigestibility-Step3and4,Finisher........................................................................................................................105
15. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsoninsituruminaldrymatterdegradability................................................106
16. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsoninsituruminalorganicmatterdegradability........................................107
17. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsoninsituruminalneutraldetergentfiberdegradability.......................108
18. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsoninsituruminalaciddetergentfiberdegradability..............................109
19. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsoninsituruminalhemicellulosedegradability..........................................110
20. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonfeedingbehavior-WheatHay,Step1and2............................................111
21. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonfeedingbehavior-Step3and4,Finisher.................................................112
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LIST OF FIGURES
1. EffectsofABVistayeast(Saccharomycescerevisiae)onapparenttotaltractnutrientdigestibilityofnaturalprogrambeefsteersfedsteam-flakedcorn-basedfinishingdiets...................................................65
2. EffectsofABVistayeast(Saccharomycescerevisiae)onapparentfiberfractiontotaltractnutrientdigestibilityofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet..........................66
3. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonaverageruminalpH..........................................................................................113
4. Effectofcottonburrsoralfalfahayasaroughagesourceduringtheadaptationperiodtosteam-flakedcorn-basedfinishingdietsonaverageammoniaconcentration(mg/L)...............................................114
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CHAPTER I
REVIEW OF LITERATURE
Natural Program Beef Production Methods
Introduction
Current conventional production methods used by the beef cattle industry
have become targets of public scrutiny in recent years. This is specifically in
regards to growth promoting technologies and antibiotics, which improve feed
efficiency and prevent beef cattle illness (Nayga, 1996, Flint and Garner, 2009).
Some methods used to enhance cattle growth are ionophores, steroidal implants
and beta agonists. Ionophores alter the ruminal environment by shifting the
growth of microorganisms from gram-positive bacteria that produce methane to
gram-negative bacteria, improving gain efficiency (DiLorenzo and Galyean,
2010). Steroidal implants are inserted into the ear of cattle and release estrogenic
hormones over time to improve growth performance throughout the growing
phase (Preston et al., 1995). Another growth promoting technology is beta-
agonists; fed to cattle during the last 28-42 days in the feedlot to improve growth
performance and lean tissue accretion during the final growth phase (Loneragan et
al., 2014). Recent concern has been on the increasing rates of antibiotic resistance
in human medicine. Although many of the antibiotics used in feedlot production
are not related to human medicine, consumers are still apprehensive. As a result,
producers are being governed into practicing more judicious use of antibiotics.
Despite the conflict of ideas regarding production methods and technology use,
the production sector still relies on consumer demand to market their beef (Knight
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and Warland, 2004). If consumer demands are not met, they could potentially
switch to other sources of protein, decreasing demand for beef. As the global
middle class is set to increase in the next few years and with it the amount of
disposable income available to afford animal protein sources grows, the beef
industry needs to work to keep beef at the center of the plate (Flint and Garner,
2009). Although growth-promoting technologies such as direct fed antimicrobials,
beta agonists, and steroidal implants improve growth performance and
sustainability of the beef cattle industry, public distrust is helping fuel an increase
in research of natural growth promoting technologies, such as yeast. This can be
viewed as an opportunity, and diversifying the beef cattle market may add a
premium producers need to improve profit margins.
Direct fed microbials (DFM) are used by the beef industry to improve
animal performance (McAllister et al., 2011, Robinson and Erasmus, 2009, Flint
and Garner, 2009), with the simultaneous intent to reduce reliance on sub-
therapeutic antibiotics in beef cattle diets. Direct fed microbials can be fed in
bacterial or fungal form, and can be administered to cattle either through a bolus
or mixed directly with the feed (McAllister et al., 2011, Ghorbani et al., 2002).
There has been inconsistent data about whether or not DFM in the diet improves
growth performance of beef cattle in the feedlot (Desnoyers, et al., 2009). This
has resulted in a need for research into how these products can improve nutrient
utilization in various feeding strategies. This will be a difficult task in diets that
are already highly digestible. Yeast is classified as a microbial growth factor
because it modifies the rumen environment to encourage cellulolytic bacterial
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growth through a reduction in lactic acid production (Swyers et al., 2014). The
objective of this review was to observe the use of yeast in the diet of cattle and
view its impact on beef feedlot production.
Conventional and Nonconventional Production
Comparing conventional and natural program fed steers is one that is a
great challenge because many different products are available to both systems to
improve growth performance. Much research suggests natural program steers are
less efficient because they do not have access to growth promotants such as
ionophores, implants or beta agonists, and have greater incidences of liver
abscesses without access to sub-therapeutic antibiotics in the feed. As well as
reducing reliance on sub therapeutic antibiotics, steroidal implants and beta
agonists, natural feedlot diets generally include higher levels of roughage to
reduce the risk of digestive upsets and liver abscesses (Maxwell et al., 2014). In a
meta-analysis by Wileman et al. (2009), researchers evaluated implanted versus
non-implanted cattle, and those that received metaphylactic treatment on arrival
compared to those that did not. The difference between steers in conventional
versus nonconventional programs was improved ADG by 0.25 kg/d, increased
DMI by 0.53 kg/d, and improved G:F by a factor of 0.02. Unfortunately, models
such as this do not include the use of DFM and management strategies of the
cattle, so differences between programs are difficult to tell. Some natural
programs allow the use of ionophores to control for coccidiosis, which also
improves gain efficiency of cattle in natural programs (Wileman et al., 2009).
Another difference between natural and conventional programs is the morbidity
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and mortality rate during the feedlot production system. Wileman et al. (2009)
noted cattle not fed tylosin in the diet had 30% liver abscesses, while those fed
tylosin had 8% liver abscesses. Capper et al. (2012) evaluated all systems in beef
production and determined that conventional production was the most efficient,
but also determined all production systems were sustainable and improving in
terms of production efficiency. Growth promoting technologies improve growth
performance of beef cattle, however, their social acceptability is becoming an
issue and more effective communication with consumers is necessary (Wileman
et al., 2009). Adding diversity to the beef industry benefits producers who desire
to improve the profitability of their operation (Maxwell et al., 2014). All
production systems may be viable options for producers and are dependent on
their customer, their values and the economics of such a decision.
Direct-Fed Microbials
A DFM is defined as “a source of live, naturally occurring
microorganisms” (Yoon and Stern, 1995). Products researched have been
methane inhibitors, propionate enhancers, and microbial growth factors (Yoon
and Stern, 1995). Probiotics are described by the FAO-WHO (2001) as “live
microorganisms which, when administered in adequate amounts, confer a health
benefit on the host” (FAO-WHO, 2001). The term DFM includes all microbial
cultures, extracts, and enzymes, which benefit the environment of the digestive
tract and animal health. The mechanisms of action of most DFM are not well
understood, due to the inconsistency of results and the wide variety of products
available (Krehbiel et al., 2003). Direct fed microbials can have multiple effects
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on the animal ranging from improved nutrient digestibility to decreasing
morbidity (Yoon and Stern, 1995). The original intent of feeding DFM was to
improve the establishment of beneficial gut microbiota during stressful periods in
the ruminant’s life, such as introduction to the feedlot (Ghorbani et al., 2002).
Following further research, it was observed DFM might have the ability to
improve growth performance of the animal (Ghorbani et al., 2002).
The goal of ruminant nutritionists is to manipulate ruminal microbiota to
maximize utilization of the nutrients in the diet (Yoon and Stern, 1995). Ghorbani
et al. (2002) observed including DFM in feedlot diets decreased ruminal
amylolytic bacteria, which are responsible for starch degradation (Chaucheryas-
Durand et al., 2008). This results in a more desirable environment for cellulolytic
bacteria to grow and increasing fiber digestibility. Direct fed microbials may be
included as part of a feedlot finishing diet as a tool to combat the negative effects
of acidosis, improving beef cattle growth performance (Ghorbani et al., 2002).
Other uses for DFM include, preserving silages and haylages to provide a safe,
nutritious and viable ingredient for beef cattle diets (Yoon and Stern, 1995).
Considering the lack of knowledge concerning the gastrointestinal environment of
beef cattle, the use of DFM and understanding their modes of action is imperative
to help better understand the rumen environment and its role in digestion.
Inconsistent results between studies suggests more research is necessary to
observe the strains of yeast, different levels and their handling procedures are
needed to achieve improved results every time yeast is included in the diet.
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Probiotics
Probiotics are a bacterial class of DFM used to improve growth
performance of beef cattle by developing the gastrointestinal tract environment.
The probiotics generally utilized are those that improve the growth of lactic acid
producing bacteria within the rumen. Some probiotics that have been fed to
ruminants are Propionibacterium and Enterococcus faecium (Ghorbani et al.,
2002). When cattle consume high concentrate diets, lactic acid is produced by
ruminal microbiota causing a reduction in the ruminal pH. These bacterial species
encourage the production of lactic acid before high concentrate diets are
introduced, because the rumen is better equipped to combat lactic acid when high
starch diets are consumed (Beauchemin et al., 2003). As a result, ruminal
microbiota adjust more efficiently to the influx of lactic acid, reducing acidosis
risk and any ensuing liver abscesses (Beauchemin, et al., 2003). These bacterial
species also have an effect on the rumen environment and help increase protozoal
numbers within the rumen (Ghorbani et al., 2002). Protozoa are responsible for
consuming starch and utilizing it at a later time, reducing acidosis risk by slowing
the digestion of starch (Ghorbani et al, 2002). Adding probiotics to the diet is
beneficial for ruminal fermentation variables by improving the ruminal
environment.
Yeast
Yeast products are a class of DFM used by the beef industry to modify the
rumen environment to improve cattle growth performance (Kung et al., 1997,
Yoon and Stern, 1995). Yeast generally comes in an active dry form (ADY),
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which has been freeze-dried to preserve its activity. It can also be mixed with a
medium in which to ferment (Chaucheryas-Durand et al., 2008). Yeasts are not
currently regulated by the FDA, but have been placed on the Generally
Recognized as Safe list in North America. Due to the fact yeasts are not regulated,
their product quality may not always be consistent. However, most companies are
attempting to have the yeast products that are viable at greater than 10 billion
colony forming units (CFU) per gram (Chaucheryas-Durand et al., 2008). Yeasts
provide a natural alternative feedlot for systems to improve production without
depending on antibiotics. Yeasts have helped to improve dairy production and
growth performance in feedlot cattle (Chaucheryas-Durand et al., 2008).
Mechanisms of Action
One purpose of including yeast in the diet is to stabilize the rumen
environment when cattle are fed high-concentrate diets (Chaucheryas-Durand et
al., 2008, Vyas et al., 2014). In a review by Yoon and Stern, (1995), they reported
findings from as early as 1950, which attributed altered ruminal fermentation
patterns due to yeast included in the diet. Zinn et al (1999), observed no effect on
ruminal pH or VFA molar proportions within the rumen for steers fed diets with
yeast. Other studies have observed using yeast increased the average rumen pH in
dairy cattle (McAllister et al., 2011). Inconsistent results between studies suggests
more research is necessary to observe the strains of yeast, different levels and
their handling procedures are needed to achieve improved results every time yeast
is included in the diet.
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A concern with increased ruminal pH results from these studies is many
have been derived from dairy cattle (Desnoyers et al., 2009, Thrune et al., 2009).
This could influence the outcomes of many studies because dairy cattle have
greater DMI than beef cattle. In a meta-analysis by Desnoyers et al. (2009)
observed ruminal pH levels by 0.03 when yeast was included in the diet.
Concentrations of VFA within the rumen increased in the diet on average of 2.17
mM when yeast was included in the diet (Desnoyers et al., 2009).
The average ruminal pH values were greater in yeast-supplemented cattle
with a pH of 6.53 vs. the control at 6.32, as well as maximum pH values of 7.01
vs 6.80, and minimum pH values of 5.97 vs 5.69 (Thrune et al., 2009). The
increase in ruminal pH helps to combat acidosis because the animals spend less
time in the sub-acute acidosis zone between 5.60 and 5.00, which provides a more
stable ruminal environment for the ruminal microbiota. However, a concern is the
amount of time the rumen spends in the sub-acute acidosis level at a pH between
5.00 and 5.60 (Gonzalez et al., 2012). Thrune et al. (2009) and Vyas et al (2014),
observed the rumen environment spent less time below a pH 5.60 when diets were
supplemented with yeast. Thrune et al. (2009), observed reduced VFA
concentrations in the rumen when feeding yeast, which may attribute some to the
improved rumen pH, however, this was not the same case in all studies (Newbold
et al., 1996). Vyas et al. (2014) observed both active and killed dry yeast in the
diet improved mean and minimum rumen pH, suggesting even when stored under
non-ideal conditions, yeast could still improve the ruminal fermentation
environment. While these results appear to be positive, the effect of yeast in the
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diet of growing beef steers needs to be researched further to ensure products
provide similar responses noted in dairy cattle under a variety of conditions,
whether it is in the finishing diet of feedlot cattle or used during the
backgrounding period when high roughage diets are utilized. By studying the
results from various studies, it has been hypothesized yeast may work in various
pathways throughout the digestive tract (McAllister et al., 2011).
Lactic Acid Utilization
Yeast works through various pathways in the rumen to improve nutrient
digestibility. Yeasts stimulate the growth of lactic acid utilizing bacteria, which
metabolize lactic acid within the rumen (McAllister et al., 2011, Robinson and
Erasmus, 2009, Miller-Webster et al., 2002). This results in reduced acidosis risk
and the subsequent sloughing of rumen walls, additionally reducing the risk for
liver abscesses, leading to a more stable ruminal environment (Moya et al., 2009,
Ghorbani et al., 2002). Many growth performance improvements observed when
beef cattle were fed yeast were due to stimulation of cellulolytic and lactate
utilizing bacteria in the rumen (Martin and Nisbet, 1992). When fed high
concentrate diets, a reduction in pH is inevitable as the starch is utilized quickly in
the rumen environment by microbial cells to produce VFA and lactic acid. A
reduction in pH could leave the rumen in a state of acidosis, reducing intake
consistency, creating an undesirable rumen environment (Desnoyers et al., 2009).
Wohlt et al. (1991) speculated yeast also stimulated growth factors of cellulolytic
and proteolytic bacteria in the rumen, specifically in cattle fed high concentrate
diets (> 50%), which was also observed by Wiedmeier et al. (1986) improving the
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digestibility of crude protein and fiber. Increasing cellulolytic and proteolytic
bacteria boost the energy derived from the fiber from the diet (Beauchemin et al.,
2003).
Fiber Digestibility
Including yeast in the diet of cattle fed high cereal grain diets, increased
DMI and nutrient digestibility, specifically fiber when researchers observed an
increase of 27% in cellulolytic bacteria (Weidmeier et al., 1986). In a review by
McAllister et al. (2011), fiber digestion was improved when yeast was included in
high concentrate diets of feedlot cattle. Despite the fact including yeast in the diet
improves fiber digestibility, a meta-analysis found the acetate to propionate ratio
in the rumen not influenced (Desnoyers et al., 2009). When fiber is digested, it
results in the production of acetate, and propionate is produced from the
breakdown of starch (Goad et al., 1998). In this meta-analysis, the authors also
observed as the concentrate in the diet increased, the effect of yeast on the
concentration of lactic acid in the rumen decreased by 0.9 mM (Desnoyers et al.,
2009), which would is beneficial in the feedlot industry as the level of concentrate
in the diet increases. The improvement in rumen pH creates a more stable ruminal
environment, improving the environment for cellulolytic bacterial growth.
Ideally, yeast products are used to improve the growth performance of
cattle and prevent nutritional health disorders. Saccharomyces cerevisiae is a
yeast product and requires an aerobic environment to function, and it quickly
removes oxygen from the rumen (Newbold et al., 1996). The removal of oxygen
creates an anaerobic environment in which the anaerobic bacteria found have a
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more suitable and stable environment for increase DM digestion when using two
yeast products, which was 71.6% and 69% versus 66.6% (Miller-Webster et al.,
2002). However, S. cerevisiae is an aerobic organism, and the length of time it
works within the anaerobic environment of the rumen is unknown (McAllister et
al., 2011). According to Chaucheryas-Durand et al. (2008), 16 L of oxygen can
enter the rumen throughout the day, affecting the anaerobic microorganisms, and
some yeast strains can consume the oxygen, resulting in a more desirable
environment for anaerobic microbial bacteria, improving nutrient digestibility,
and energy derived from the diet (Newbold et al., 1996).
Ammonia Uptake
A final theory on the benefits of yeast and its mode of action is it improves
ammonia uptake from the rumen, thus improving microbial protein production
through better protein recycling (Miller-Webster et al., 2002). Stimulation of
proteolytic bacteria resulted in less variation in ammonia in the rumen, suggesting
a more stable rumen environment (Harrison et al., 1988). This improved stability
implies rumen microbes have better uptake of ammonia to use when multiplying,
providing more undegradable intake protein for cattle. Beauchemin et al. (2003)
observed an increase in microbial protein flowing from the rumen into the lower
gastrointestinal tract, which might result in an increased requirement for
degradable intake protein (DIP) in growing cattle. However, of all mechanisms of
action, this has been the least documented effect of yeast inclusion in the diet
(Miller-Webster et al., 2002). By utilizing more dietary energy, the animal
improves growth performance.
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Supplementation
When including yeast in the diet of growing cattle, it is important to
consider the many different aspects of yeast that affect its viability. The FDA does
not regulate yeast, so researchers and producers need to be cognizant of the
conditions under which the yeast was handled. Yeast is generally sold as an active
and living organism, and it could be inert if stored improperly. Storing yeast
under conditions that allow it to remain inactive until it comes into contact with
the rumen is most ideal. The different varieties of yeast available affect how the
yeast acts within the ruminal environment. The following sections further
evaluate how yeast should be fed and the direct effect of handling on the
production of the animals involved. Similar to other feed additives; precise levels
and conditions are necessary to reap the best benefits for the cattle and their
performance. Yeast is a unique product that can impact many areas of the beef
production cycle, so its impact during various phases of the animal’s life needs to
be evaluated further.
Levels
The amount of yeast included in the diet can be dependent on strain,
production, colony forming units of the yeast, and intake of each animal.
Researchers observed when cattle were placed in stressful conditions adding yeast
to the diet increased DMI (Yoon and Stern, 1995). However, the inclusion of a
dried yeast culture grown in a corn medium from 1 to 2 % of the diet did not
increase DMI further from 6.2 kg/day to 6.4 kg/day, compared to the control diet
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of 5.6 kg/day, suggesting optimal levels to be included in the diet on a DM basis
is 1 % (Yoon and Stern, 1995). The ability of yeast to effect growth performance
depends upon biotic factors such as the yeast strain and its viability as well as
abiotic factors such as storage conditions, animal management and the diet
(Chaucheyras-Durand et al., 2008). Scientists have been selecting yeast strains
based upon their ability to effect ruminal microorganism populations
(Chaucheyras-Durand et al., 2008). Many research trials have used yeast in the
diet at levels of 1% inclusion on a DM basis. Depending on the comparative
intake of the animals being addressed, keeping the yeast levels at beneficial
concentrations would be best for improved production.
Activity
The variety of yeast products available, their viability (killed versus
active), environmental conditions they are stored could affect their capability to
improve growth performance. According to Sullivan and Bradford (2011), an
issue with using ADY is the lack of quality control in regards to these products by
the FDA. A potential reason for some of the issues with inconsistent results from
using yeast is due to the lack of quality control within the products. Sullivan and
Bradford (2011) found exposing ADY to temperatures above 40°C for a period of
two weeks dramatically reduced their activity. When exposed to higher
temperatures, ADY colony forming units were activated, and due to a lack of
available nutrients, they became inert, by as much as 90% over a period of 3
months above 40ºC (Sullivan and Bradford, 2011). The issue with including yeast
products within a vitamin and trace mineral complex is some minerals can oxidize
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and lyophilize the yeast making the yeast cells inactive (Sullivan and Bradford,
2011). However, it is hypothesized including strong antioxidants within the
vitamin trace mineral premix along with the yeast product; the antioxidants could
protect yeast viability (Sullivan and Bradford, 2011, Walker et al., 2006).
The average time heifers had a rumen pH below 5.80 and 5.60 was
reduced when either a killed dried yeast (KDY) or ADY was supplemented in the
diet of ruminally cannulated beef heifers (Vyas et al., 2014). Yeast can reduce the
risk of sub-acute and acute acidosis in cattle diets, irrespective of whether it is
active or dry. This suggests yeast viability may not be as negatively affected due
to adverse environmental conditions as first hypothesized (Vyas et al., 2014).
Vyas et al. (2014), found supplementing either ADY or KDY in the diet does
affect overall nutrient digestibility, but it may depend on yeast strain. That being
said, the effect of KDY on other aspects of growth performance and the rumen
environment were not studied, and before accepting KDY as an acceptable
product.
Diet Digestibility
There has been an assortment of experiments discussing the efficacy of
yeast to improve digestibility of crude protein (75.4 % vs. 73.8%) and cellulose
(66.3% vs. 61.0%) (Wohlt et al, 1991). As noted previously, yeast improves fiber
digestibility by providing an environment for cellulolytic bacteria to grow and
reproduce. There have been some studies, however, that have also recorded
improved protein, starch, DM and OM digestibility when yeast was included in
the diet as well. Callaway and Martin (1997) observed improved growth of
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ruminal bacteria in a laboratory setting when exposed to yeast filtrates. As a
result, it has been hypothesized yeast provided nutrients required by ruminal
microbes such as B vitamins, amino acids and organic acids (Callaway and
Martin, 1997). With improvements in growth factors for ruminal microbes when
fed high concentrate diets, yeast may provide nutrients for those microbes. In a
meta-analysis by Desnoyers et al. (2009), OM digestibility was increased via the
supplementation of yeast products in the diet of ruminants. Supplementing yeast
in the diet whether it was ADY or KDY improved the overall apparent total-tract
digestibility of starch without affecting the digestibility of other nutrients (Vyas et
al., 2014). Increasing starch digestibility may be another reason for increased
rumen pH when beef cattle are fed yeast products. Yeast can utilize starch in its
reproductive process, reducing the starch available in the rumen for microbes
(Vyas et al., 2014). Improved starch digestibility is not a response that was easily
replicated in other studies when yeast was used as an additive in the diet.
However, if it can be replicated, that would be extremely beneficial for the beef
industry because it would result in less grain needed to feed the animal, improving
sustainability of the beef industry.
Health
Increasing concern about antibiotic resistance and more stringent
regulations concerning antibiotic use, the adoption of yeast in finishing diets of
beef cattle to improve growth performance appears to be beneficial. Feeding yeast
products in the diet rather than sub-therapeutic antibiotics could potentially reduce
the transfer of resistant bacteria into the human food chain (Chaucheyras-Durand
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et al., 2008). How cattle respond to yeast also depends upon their physiological
status, it appears yeast in the diet is more effective when fed to stressed animals
(Chaucheyras-Durand et al., 2008). Using yeast culture in receiving diets
improved the cattle response to antibiotic therapy and reduced the days needed to
recover from an Infectious Bovine Rhinotracheitis Virus (IBRV) infection (Cole
et al., 1992). In a study researching yeast influence on morbidity and total sick
days in recently weaned growing cattle, it reduced morbidity overall, as well as
reduced the total number of sick days (Zinn et al., 1999). However, at the end of
the growing phase, yeast supplementation did not impact growth or digestive tract
function (Zinn et al., 1999). While growth performance is not always replicated in
yeast supplementation trials, if health were improved in stressed calves, it could
reduce reliance on antibiotics. While many producers believe most of the stress
cattle are under is during the receiving phase to the feedlot, some stress may occur
during the finishing phase when cattle are growing very large and are living in
poor weather conditions. Yeast appears to be very beneficial in keeping DMI
consistent during the finishing phase because it helps reduce the negative effects
the cattle feel from stressful situations, such as the adaptation period to high
starch diets.
Risk of bloat is a concern when cattle are introduced to the feedlot and
adapted rapidly to high concentrate diets. Bloat is caused by the production of
mucopolysaccharides, which increases the viscosity of rumen fluid and increases
the risk to develop frothy bloat, causing a decrease in animal performance and
potentially death (Moya et al., 2009). Adding yeast to the diet under induced
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acidotic conditions reduced the overall viscosity of the rumen fluid reducing
frothy bloat risk (Moya et al., 2009). Considering young, high-risk cattle in the
feedlot have a higher risk for bloat as they adapt to high concentrate diets, the
addition of yeast may improve performance of the feedlot and cattle as they grow
through the finishing phase.
Growth Performance
Cattle need to have a consistent DMI, especially during the initiation to
the feedlot, when stress levels are high, causing a risk for compromised health
(Keyser et al., 2007). It was observed feeding yeast to newly received heifers in
the feedlot resulted in heifers returning to a normal DMI more quickly after
needle injections (Keyser et al., 2007). Many researchers argue the capability of
yeast products to improve DMI in growing steers, as many have had conflicting
results as to how much influence yeast has on growth performance (Zinn et al.,
1999). Contrary to the results observed by Zinn et al. (1999), researchers Phillips
and VonTungeln, (1985), were able to report improved ADG by 0.10 kg/day of
growing feedlot steers when fed high concentrate diets (53% corn) were
supplemented with yeast. Yoon and Stern (1995) reported live weight gain
increased by as much as 19% in Friesian male calves when fed a barley/soy diet
that included yeast. However, different results could be obtained in terms of
growth performance based on differing diets from each region and production
system. According to Moloney and Drennan, (1994), the inclusion of yeast in the
diet of growing cattle improved cattle growth performance of animals fed a grass
silage diet with barley-based concentrates. In a study by Moloney and Drennan
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(1994) they observed improved growth performance of cattle fed high concentrate
diets with yeast inclusion rather than high roughage diets. Recently weaned feeder
steers, which were fed yeast in the diet, had fewer sick days and greater DMI’s
than those calves whose diet did not include yeast (Cole et al., 1992). When
supplementing steers with yeast, Swyers et al. (2014), recorded reduced ADG by
0.14 kg/day compared to cattle not fed any yeast in the diet. Feeding cattle diets
with yeast products improved overall DMI during periods of stress (Cole et al.,
1992). When fed in combination with Selenium and Chromium supplements in
grower lamb diets, yeast improved DMI and increased ADG in lambs by 250 g
per day (Hernandez-Garcia et al., 2015). Overall, it appears yeast supplementation
has a greater effect on ruminal fermentation variables, but this effect does not
directly translate into improved growth performance throughout the growing
phase of beef cattle, because nutrient digestibility appears to be improved, while
improvements in growth performance are not noted as often.
Carcass Characteristics
Yeast supplementation in the diet may improve carcass characteristics.
Supplementing the diet with a yeast product resulted in more carcasses being
graded USDA Choice, in a study comparing yeast supplementation to monensin
(Swyers et al., 2014). When steers were supplemented with a S. cerevisiae as an
alternative to monensin, they had a similar final BW but lower ADG (Swyers et
al., 2014). As mentioned before, improvement in carcass characteristics are
generally not noted because cattle in natural programs are generally fed for longer
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periods of time, resulting in more time for fat deposition within the muscles,
which improves carcass characteristics such as marbling.
The addition of yeast in the diet did not affect carcass characteristics such
as HCW, carcass quality, or yield grade (Hinman et al., 1998). Similar results
were observed in lambs fed yeast products during the finishing phase (Hernandez-
Garcia et al., 2015). However, carcass response may have been partially attributed
to the age of the lambs at slaughter, as the lambs did not have enough time to
physiologically respond to the yeast (Hernandez-Garcia et al., 2015). Contrary to
these results, Mir and Mir, (1994), found adding a live-yeast culture to the diet in
growing finishing feedlot steers it improved final weights and carcass weights of
steers when fed rolled barley based diets over control diets. When yeast cultures
were mixed with a lasolacid additive (an ionophore) to the diet however, no
additive effects were seen within the steers in either growth or carcass
characteristics, unlike would be expected because it has been hypothesized they
work with different modes of actions (Mir and Mir, 1994). Ionophores work
through affecting the ion balance of gram-positive bacteria, while yeast works
through improving the growth of bacteria that utilize lactate, causing an improved
environment for cellulolytic bacteria. If an additive effect had been observed, this
would be positive news for beef producers who own natural program cattle trying
to emulate conventional practices in terms of growth performance.
Cost
Cattle fed yeast alone are less efficient than those animals fed a monensin
based diet, and it costs 5.82% more to feed them than conventionally raised cattle
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if diet costs are equal (Swyers et al., 2014). That being said, some consumers are
more willing to pay a premium for these naturally raised animals. Nonetheless,
before entering into a natural program, ensuring a market for these animals is
imperative, or the producer will be forced to take conventional prices while
raising cattle at a lower efficiency and higher cost (Swyers et al., 2014).
Dependent on cost of ingredients and cattle, yeast could be beneficial to feedlots
that are not only focus on natural production, but those feedlots looking to reduce
stress in cattle in all phases of production. According to Swyers et al. (2014),
natural producers need a premium of 6% to realize a profit if yeast products were
included in a high concentrate diet that included 63.5% steam-flaked corn.
Implications
Like many products used within the beef industry, producers have to be
cognizant of feeding at high levels, and discover adequate levels of inclusion
within the diet to enhance growth and production of the animal without impeding
health (Yoon and Stern, 1995). Yeast inclusion in the diet decreased morbidity of
steers during the receiving phase at the feedlot; however, many studies did not
research the effects of yeast in the diet during the finishing phase of the feedlot,
which may have an impact during a longer feeding trial (Keyser et al., 2007).
Conclusions
Although further research is required to study dose and strain of yeast to
be used in beef cattle diets to improve growth performance, there appears to be an
advantage in using yeast. Unfortunately, the results observed thus far in research
in terms of improvement of growth performance and carcass characteristics have
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been inconsistent and need more validation to be adopted wholly in the beef
industry. However, improvements that have been noted may be valuable to those
producers who are marketing their animals to niche markets and are looking to
improve their performance. In conclusion, with the natural beef production niche
growing and with the increasing vocalization of the consumer community, it is
imperative to treat the results of the studies using DFMs and probiotics in feedlot
diets very seriously as we look to alternatives to sub therapeutic use in
concentrated animal feeding operations, specifically within the beef industry.
Considering the cost of beef production, the beef industry needs to be proactive to
consumer concerns because their product costs much more than other protein
sources. Producers need to be able to sell it as a safe and affordable product to be
enjoyed by all consumers. The major effect of yeast is it improves the ruminal
fermentation environment when cattle are consuming differing diets and under
stressful conditions. Similar to ionophores, yeast modifies the rumen
environment, helping to make it more stable for the rumen microbes, thus
improving the digestibility of the diet and the health of the animal.
The objective of this research trial was to evaluate the effect of yeast in
natural program steers on steer growth performance, total tract apparent nutrient
digestibility, feeding behavior and carcass characteristics. The authors were
anticipating an improvement in growth performance and apparent total tract
nutrient digestibility with increasing levels of yeast in the diet. Yeast was
included in the diet to be targeting on average 0, 25 or 50 grams per head per day.
Increasing levels was thought to further improve and stabilize the ruminal
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environment, thus translating to improved growth performance throughout the
finishing phase and total tract apparent digestibility. With improved growth
performance, it was also thought some carcass characteristics such as rib-eye area
would be improved. Improving natural program steer growing programs was the
intent because they cannot use conventional methods that improve performance.
Natural producers are looking for a natural alternative to improve cattle growth
without using implants, antibiotics or beta agonists. This study observed the effect
of yeast in steers fed steam-flaked corn-based finishing diets, and focused on the
finishing phase of steers in the feedlot. The following chapter discusses the effect
of yeast used in natural program steers fed a steam-flaked corn-based finishing
diet.
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ADAPTATION OF BEEF FINISHING STEERS TO HIGH
CONCENTRATE FINISHING DIETS
Introduction
Improving the growth performance of cattle in the feedlot is important to
develop efficiency and reduce the cost of gain. As beef cattle adapt to a high
concentrate finishing diet from a high roughage based diet, it has to occur over
time to acclimate the rumen environment. During this transition period, bulky
high fiber ingredients are required to provide the roughage needed to initiate
rumination and provide gut fill. An issue with the adaptation period in the feedlot
is it uses high levels of roughages accounting for 50% of the total roughage costs
of the feedlot period. (Mader et al., 1993) These roughage sources, such as alfalfa
hay, are expensive per unit of energy because of their low energy density. Due to
their high logistical costs, finding new and low cost ingredients to utilize during
the adaptation period would be beneficial. A benefit of cattle is they can utilize
low quality forages to produce high quality protein. There are a lot of low quality
roughages available in most regions available. The concern is not all roughages
have been studied in the feedlot setting, so their ability to replace traditionally
used roughage sources during the adaptation period is not always well understood.
How an animal responds to new roughage sources is not always well researched,
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and rumen variables and digestibility of the diet during the period, and how it
affects the animal in the finishing phase need to be further elucidated.
Co-products can be utilized in replacement of traditional bulky ingredients
such as alfalfa hay. The advantage of co-products is they are generally high in
fiber and are not usable to industries other than in livestock production. Co-
products are available from a variety of industries, DDGS from ethanol
production and WCGF from wet corn milling, or cotton burrs from cotton
production in the southern plains. These products have generally had the energy
(starch) removed for the primary industry they are involved in, leaving a
concentrated source of fiber and other nutrients for cattle to consume. These are
generally bought at a lower price and fulfill the need for roughage source in
adaptation strategies, reducing demand for alfalfa hay. These roughage sources
help the rumen environment adapt to high starch diets. This could provide
physically effective fiber, which stimulates rumination, resulting in more saliva,
buffering the rumen, and reducing sub acute and acute acidosis risk. Depending
on the nutrient composition of the byproduct utilized, each can have varying
benefits on beef cattle performance, which is the reason for researching adaptation
strategies.
Cotton burrs, more commonly known as gin trash in the southern regions
of the United States, are widely available as a byproduct of the cotton processing
industry, made up of the immature bolls, stems and leaves. Cotton is commonly
grown in the southern United States, resulting in cotton burrs being widely
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available and might provide an economic benefit for feedlots if its use can be
justified during the adaptation period to high concentrate diets in the feedlot.
Although inexpensive, effect on steer acceptance and consecutive effect on
growth performance is necessary before using it as a roughage source in the
adaptation process in the feedlot. If cotton burrs can be used in place of alfalfa
hay in the adaptation period of the feedlot, feedlots could potentially reduce
overall cost of feeding the cattle and improve their profit margins, all the while
not compromising the health of the cattle.
Adaptation Period
The primary goal of the adaptation period is to familiarize rumen
microbiota to high levels of starch without harming the growth performance of the
animal or the ruminal environment. Adapting the rumen requires a shift from
cellulolytic bacteria, which typically degrade cell wall, to amylolytic bacteria,
which more effectively digest starch (Bevans et al., 2005). Doi and Kosugi,
(2004) predicted 80% of the energy needs and 50% of the protein needs of a
ruminant come from the ruminant microbiota, resulting in a need to keep the
microbial population stable throughout the feedlot phase in order to maintain
growth performance. When cattle diets are abruptly switched from high roughage
to high concentrate, the resulting decrease in pH is largely due to the increased
production of lactic acid (Owens et al., 1998). This drop in pH causes the demise
of microorganisms, harming the rumen and causing liver abscesses and a resultant
reduction in growth performance or even death (Owens et al., 1998). When
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evaluating new roughage as a viable source in adaptation diets, the rumen
environment, health, growth performance and carcass characteristics all need to
be evaluated. Unfortunately, rumen response has not been well documented for
different adaptation strategies (Leedle et al., 1995). Studies that evaluate
metabolic response do so in week long periods, which do not challenge cattle as
much as diets which are stepped up over a period of days rather than weeks.
Research evaluating shorter periods of time for adaptation generally evaluates
beef cattle growth performance rather than metabolic response which can be
observed in ruminally-cannulated steers. A lot of the variation in length and
concentration of roughage in the diet depends on the management of the cattle,
their geographic location, their background, the environment and the nutrient
requirements of the cattle.
Restricting the intake of cattle during the adaptation is a tool to help
reduce inconsistencies in intake and helps cattle more effectively adapt to high
concentrate diets (Choat et al., 2002). Reducing fluctuations in intake during the
adaptation period could help cattle respond to the drop in pH more effectively as
well as reduce digestive upsets due to increased high concentrate loads. Leedle et
al. (1995) reported cattle were stressed when fed diets which continually differed
in nutrient concentration and caloric values at intakes greater than 2% of their
current body weight. Choat et al. (2002), Bierman and Pritchard (1996), and
Weichenthal et al. (1999) observed that restricting dietary intake during the
adaptation period of the feedlot phase reduced total DMI during the period and
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27
improved feed efficiency. The issue with restricting feed intake during the
adaptation period is it may reduce growth performance of the cattle, placing them
at a disadvantage during the finishing phase (Choat et al., 2002). Finding balance
between those restricted intakes without decreasing growth performance is
difficult to achieve. Another option of adapting cattle to a high concentrate diet is
the use of bunk management to control the intake of growing cattle. When cattle
have ad libitum access to feed, generally a reduction in intake occurs after a
period of time, due to overconsumption of grain, leading to a reduction in ruminal
pH, leading to acidosis and health issues, reducing intake (Tremere et al., 1968,
Brown et al., 2006).
Methods
There are many methods to adapt cattle to high concentrate diets
efficiently and safely. The issue with adapting cattle to high concentrate diets,
which has been mentioned earlier, is the fact it can cause digestive upsets such as
acidosis and bloat if it done too quickly (Kunkle et al., 1976). The most common
method of adapting cattle to high concentrate diets going from a diet of 55%
concentrate to 90% concentrate over a period of 14 days or less (Brown et al.,
2006). This increase in concentrate can cause reduced performance due to dietary
upsets from the high-energy diet and influx of lactic acid (Brown et al., 2006). In
a study by Brown et al. (2006), it was observed limiting the intake in the diets
versus ad libitum of steers during the first 28 days of the feeding period, the
animals consumed less and gained more efficiently than animals fed higher
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28
energy levels during the same period. This continued to the end of the feeding
period, where cattle that were initially limited had a 4% improved feed efficiency,
despite having clumped papillae in their rumens at slaughter (Brown et al., 2006).
Other studies studying a 7 day adaptation period with increasing concentrate in
the diet from 55 to 95% found reduced ADG by 10%, and reduced G:F by 9%,
compared to those over 14 days (Brown et al., 2006).
Ingredients, Time, and Sorting
There are many tools available to feedlots to adapt cattle to finishing diets.
While diets can vary from feedlot to feedlot the same basic structure of each diet
remains intact, which is decreasing roughage balanced by increasing concentrate.
Along with common ingredients, producers can also utilize growth-promoting
technologies to allow animals to grow more quickly and efficiently. These
technologies include steroidal implants to increase lean accretion and ionophores
are commonly used to help stabilize the rumen environment to improve
efficiency. In a study by Galyean et al. (1992), researchers observed the effect of
including laidlomycin propionate and monensin plus tylosin on the growth
performance of feedlot steers during the adaptation phase. Laidlomycin
propionate yielded improved rates of gain of 2.6% over control steers, and 4.2%
over the monensin/tylosin treated steers. Monensin is the ionophore of choice
because it reduces DMI during the finishing phase, improving G:F ratios.
Laidlomycin is not known for these properties; however, Galyean et al. (1992)
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29
observed feeding laidlomycin propionate was just as effective to feed during the
adaptation phase as monensin.
When cattle enter the feedlot, they can potentially be stressed due to
travel, recent weaning, and mixing of cattle from different backgrounds. This
stress causes a reduction in feed intake, further depressing the activity of their
immune system. This stress can cause as much as a 75% reduction in rumen
fermentative activity, and can stay decreased for as long as five days later (Loerch
and Fluharty, 1999). Decreased DMI due to stress coupled with an increase in
concentrate in the diet could increase the risk for acidosis and bloat, as the rumen
environment cannot handle the changes it is placed under. During the stressful
periods, cattle require higher nutrient densities to meet their needs while they
have decreased DMI by as much as 38% (Loerch and Fluharty, 1999). Increasing
the energy density of the diet may harm the ruminal microorganisms because of
the readily available starch in the diet (Loerch and Fluharty, 1999). The
adaptation of cattle to new diets involves the introduction of new diets every few
days; causing a reduction in DMI, shocking ruminal microorganisms with rapid
pH drops. In more recent research, it has been observed cattle fed diets with
industry recognized RAMP (Cargill), can be adapted to diets more quickly than
usually while improving ADG by 0.09 kg/day throughout the finishing phase and
HCW by 8.00 kg (Anderson et al., 2015). This can be explained by the fact
RAMP is composed of highly digestible fiber which provides a rumination source
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30
while decreasing reliance on high fiber, low energy dense sources which are not
as digestible (Anderson et al., 2015).
In a study by Mader et al. (1993), the authors observed a tendency
increased liver abscess scores (1.34 vs 0.91) for animals adapted to a high
concentrate diet with alfalfa hay over alfalfa silage. They hypothesized this result
is seen because more sorting occurs with dry feeds over wet feeds. Feeding a
silage rather than hay as a roughage source in adaptation diets improves gains and
intakes, which may be harmful when studying cotton burrs as part of the
adaptation diet because they are extremely dry and large which could result in
more sorting and reduction in growth performance. Perhaps more grinding to
make a more consistent product to mix in with the rest of the diet would help to
decrease sorting, but that adds extra costs to the maintenance and labor needed to
take care of the roughage source.
Health
Acidosis
Acidosis is a metabolic disorder occurring when there is a digestive upset
within the rumen due to a sudden high starch load (Gonzalez et al., 2012).
According to Galyean and Rivera (2003), although mortality rates are low within
the feedlot at less than 1%, a staggering 30-42% of those deaths are due to
digestive disorders. There are two types of acidosis, sub-acute and acute. Acute
acidosis occurs when the ruminal fluid is at a pH of 5.0 or lower and sub-acute
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31
appears when rumen pH is between 5.00 and 5.60 (Owens et al, 1998 and
Nagaraja and Titgemeyer, 2007). Sub-acute acidosis rarely shows clinical
symptoms, but it potentially decreases growth performance of the animal, while
acute acidosis causes clinical symptoms and sometimes death (Owens et al.,
1998) being very costly to the beef industry. Acidosis is a risk during the period
of adapting cattle because cattle are being rapidly switched from a high roughage
diet to a high concentrate diet could shock rumen microorganisms as they digest
large amounts of starch, increasing the lactic acid load dropping the rumen pH
resulting in acidosis, because microbes do not further utilize lactic acid (Nagaraja
and Tigemeyer, 2007). The acidotic rumen may adversely affect intake, causing
inconsistent intake from day to day, further increasing the risk for acidosis as the
animal gorges on feed at random events, eats quickly and reduces rumination
production (Gonzalez et al., 2012). Increased chewing activity causes more saliva
to be produced, which buffers the acid load in the rumen (Beauchemin et al.,
1994). Adaptation is necessary in the rumen to assist microbiota to stop them
overloading the microbiota with organic acids (Gonzalez et al., 2012).
Bloat
Another side effect of rapidly changing the rumen environment in cattle is
it increases the risk for bloat (Cheng et al., 1998). Bloat, similar to acidosis,
decreases animal growth performance and poses a serious risk for fatality (Cheng
et al., 1998). Bloat is often a result of acidosis because as the rumen pH drops and
the environment becomes unstable for the ruminal microbial population to grow,
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the rumen fluid contents become less motile, causing foam to build up, resulting
in frothy bloat (Cheng et al., 1998). The froth builds up quickly, causing bloat
which is difficult to be identified and treated in time to save the life of the animal.
Foamy bloat causes death quickly in animals because the gas build-up within the
rumen places pressure on the lungs causing death within minutes (Cheng et al.,
1998, Vasconcelos et al., 2008). There are two different types of bloat, free gas
and frothy, where frothy bloat is more common in feedlot cattle (Vasconcelos et
al., 2008). According to Vasconcelos et al. (2008), the cause of frothy bloat can
be a result from insufficient roughage in the diet, which reduces rumination and
eructation. Elam and Davis (1962) observed adding mineral oil to the diet also
reduced the incidence of frothy bloat. When decreasing roughage content, the risk
for bloats increases. Additionally ionophores are used to control bloat
(Vasconcelos et al., 2008) because they change the rumen environment. The
adaptation period is extremely important in the feedlot and getting cattle to the
finishing phase without bloating is extremely beneficial. The extent to which
grain is processed effects antinutritional disorders, and if corn is steam-flaked to
lighter densities, it could predispose cattle to bloat and acidosis (Vasconcelos et
al., 2008). Ramsey et al. (2002) observed cattle fed diets with more rapidly
degradable starch had a greater risk for bloat and acidosis. There is extreme risk
for cattle to bloat with the quickly changing diet and high levels of stress cattle
are under during the first few weeks of the feedlot. Proper adaptation is necessary,
if done too quickly, cattle are at risk for bloat, but too slowly, cattle have reduced
performance and more days in the feedlot.
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Growth Performance and Feed Intake
The time during which cattle are adapted to finishing diets impacts their
performance during the finishing phase. Research of the adaptation phase has
been occurring for many years, and many different strategies have been
investigated. Kunkle et al. (1976) studied methods for adapting cattle and
observed cattle can be adapted to high concentrate diets in periods as short as ten
days, as long as the cattle were properly managed. Researchers observed cattle
adapted to high concentrate diets with corn silage performed better during the
finishing phase than cattle which were adapted to high concentrate diets without
the use of corn silage (Kunkle et al., 1976). The corn silage may set up the rumen
for a high starch load and reduced rumen pH due to the lactic acid within the corn
silage. Lactic acid prepares rumen microbes for increased acid, and when the high
starch load is consumed, the microbes will not be shocked and will efficiently
digest the ingredients. However, while corn silage prepared cattle more quickly
for a finishing diet, those cattle fed hay diets in the adaptation phase had greater
gains (Kunkle et al., 1976). This validates the idea many adaptation strategies can
be utilized by the feedlot to adapt cattle to full finishing diets. The strategy the
feedlot uses is more dependent on the cost of ingredients, management,
environment and geographic location of the feedlot.
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Sub acute acidosis causes a depression in feed intake, as mentioned
previously (Gonzalez et al., 2012, Bevans et al., 2005). This decrease in feed
intake and resulting decline in steer performance shows adequate adaptation is
necessary in order to successfully run a profitable feedlot. Bevans et al. (2005),
researched whether or not quick adaptation periods could replace slow adaptation
periods to a high concentrate diet were effective. It was found even lengthy
adaptation strategies still causes some acidosis, which may be a result of
environment, genetics, physiology or even background of the animal (Bevans et
al., 2005). When the adaptation period is lengthened, the producer runs the risk
for losing performance by not meeting the gain potentials of the animal. This
results in needing to find a balance between compromising the health of the
animals while getting the highest rate of performance out of them.
Ruminal Bacterial Community
The bacterial community within the rumen is not well understood because
of the lack of knowledge of the millions of bacteria, protozoa and fungi present
(Fernando et al., 2010). Only a few bacterial species are known at this time until
the methods for extracting and analyzing the microbes from the rumen become
more effective to study the smaller groups of microbes within the rumen.
However, even though most bacterial species are unknown, the knowledge of the
species that have been studied is improving and diets are being tailored to
encourage bacterial growth. With improvement of genetic quantitative and
qualitative technologies, more bacterial species will be analyzed in the future, and
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knowledge of the rumen will only increase, improving understanding of the beef
animal will allow for better production methods within the beef industry.
When evaluating the response of the rumen to changing diets, specifically
during the adaptation phase, it is imperative to evaluate the bacterial community
(Fernando et al., 2010). Researchers are aware a dramatic decrease in pH
negatively effects the rumen environment and negatively affects the bacterial
populations, thus potentially decreasing animal growth performance for the
remainder of the feeding period. Fernando et al. (2010), found two distinctly
different bacterial species in the rumen when the diet was of high roughage as
compared to a high concentrate diet. When fed a high roughage diet, the bacteria
Fibrobacteres, was most commonly found, as compared to a high concentrate diet
where the most common bacterial species found was Bacteroidetes (Fernando et
al., 2010). During this same study, Megasphaera elsdenii, Streptococcus bovis,
Selenomonas ruminantium and Prevotell bryantii increased considerably during
the adaptation phase, while the Fibrobacteres bacteria decreased (Fernando et al.,
2010). The more researchers can learn about the environment of the rumen, the
more opportunity they have to modify diets to meet the microbial needs of the
animal, improving the efficiency with which producers adapt cattle. Fernando et
al. (2010) found increasing the starch utilizing bacteria populations did not occur
until a diet contained a higher ratio of concentrate to roughage, despite the fact the
two previous diets were increasing the level of concentrate in the diet from zero.
When cattle are adapted to high concentrate diets, there is an increase in
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amylolytic bacteria than in cattle adapted to hay diets over a similar period of time
(Goad et al., 1998).
Cotton Burrs
The adaptation phase is a costly period in the feedlot as cattle consume
high amounts of roughage, which have low energy density and high logistical
costs. Before new roughage sources can be utilized in the diet of growing cattle,
they must first be evaluated to determine their relative roughage value in relation
to other known adaptation strategies. Cotton burrs are a byproduct of the cotton
ginning process and provide an ingredient for feedlots to use in place of costly
traditional sources while adding value to the byproduct for cotton producers.
Cotton burrs have a high fiber content, which is a requirement for adaptation diets
as cattle acclimatize from high roughage to high concentrate diets (Blasi et al.,
2002). Unfortunately, cotton burrs have not been evaluated as an additive in beef
cattle adaptation diets in the feedlot, so its effectiveness is unknown.
The potential of cotton burrs to be used as a roughage source in place of
costly traditional roughage sources such as alfalfa hay is great, especially in
locations where cotton production is extensive. Cotton burrs are derived from the
cotton production, yielding from the stripping technique, which pulls the cotton
from the plant. More cotton burrs are derived from more drought tolerant varieties
of cotton, which are more common in areas such as Texas (Conner and
Richardson, 1987). When producing cotton bales, a cotton bale that weighs 480
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pounds can yield as much as 150 to 200 pounds of cotton burrs (Stewart, 2010),
which is a lot of residue. Cotton burrs has a very low bulk density, resulting in
expensive transport costs, resulting in a product that is more available for
southern producers and those close to cotton producing regions than those who
are not (Stewart, 2010, Bernard et al., 2001).
Cotton burrs are not regularly used in feedlot diets due to its low
digestibility (Stewart, 2010). Conner and Richardson (1987) observed poor
digestion of cotton burrs due to the high lignin content of the ingredient, which is
harder for ruminal microorganisms to break down. Cotton burrs also have limited
available protein in the diet (Brown et al., 1979). They have been evaluated in
pregnant cow maintenance diet, and it has been observed cows fed diets with high
levels of cotton burrs with corn grain supplementation were able to maintain body
weight. Whiting et al., (1988), observed feeding Holstein heifers a diet that
included cotton burrs rather than alfalfa hay helped to control energy intake and
reduce overall feed cost. Some research has evaluated the use of products such as
alkali to break down the cotton burrs prior to feeding in order to improve nutrient
digestibility (Conners and Richardson, 1987). It is currently advised to use cotton
burrs as a roughage source as part of a balanced ration, and must undergo testing
because it can be variable in composition (Myer, 2007).
Brown et al. (1979) concluded including cotton burrs at no more than 60%
in the diet in place of alfalfa cattle had similar performances. Brown et al. (1979)
was also concerned about the availability of protein in the cotton burrs diet. While
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its use has primarily been as a product in pregnant cow diets, it has potential to be
a roughage source during the adaptation phase in the feedlot. Evaluating the use
of cotton burrs in the diet of growing feedlot steers could potentially alleviate
costs for the feedlot while adding value to cotton byproducts, improving the
sustainability of both industries.
Implications
The period of adaptation is necessary to acclimate the rumen of cattle to
high starch content in diets. Fortunately for feedlot operators, the way cattle can
be adapted to these high concentrate diets can be variable, allowing feedlots to be
flexible when adapting cattle based on their management, location, available
feedstuffs and the cattle. The current trend of feedlots is to reduce the amount of
time spent adapting cattle to high concentrate diets because roughly 50% of the
roughage included in the diet is used during the adaptation phase. Roughages
have a low energy density compared to grains, resulting in high costs per energy
unit. Among these methods for reducing costs to the feedlot during the adaptation
phase, two can be highlighted: the first is reducing the time spent by the feedlot
adapting the cattle to a high concentrate diet. The second option is to utilize
byproducts from other industrial processes to reduce cost of the diet. This option
also provides higher energy ingredients without having high starch levels, thus not
negatively affecting the rumen. Cotton burrs may fall under this second category,
as it is a valuable byproduct from the cotton industry. As a high fiber product and
a byproduct, cotton burrs could potentially provide an acceptable alternative to
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alfalfa hay during the adaptation phase. Cotton burrs may be a good product to
use during the adaptation phase if the cost of the ingredient outweighs the benefit.
The following study evaluated the response of beef cattle to cotton burrs in the
adaptation phase of growing steers.
Cotton burrs are readily available in cotton producing areas of Texas, and
may provide a source of roughage for the adaptation phase at a reduced cost
compared to alfalfa hay. Using byproducts as a roughage source during the
adaptation phase has proven effective in reducing the costs of the feedlot as well
as provided an opportunity for producers to utilize products specific to their
geographic location. The effect of a roughage source on the rumen during the
adaptation phase is necessary to evaluate whether a forage source effectively
combats acidosis from increasing starch loads in the diet during the ever changing
adaptation phase. The "relative forage value" of cotton burrs is unknown and
further research is required to evaluate its' value relative to a known source of
roughage such as alfalfa hay on ruminal fermentation variables.
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CHAPTER II
EFFECT OF A LIVE YEAST PRODUCT IN A FINISHING FEEDLOT
DIET ON GROWTH PERFORMANCE, DIGESTIBILITY, AND
CARCASS CHARACTERISTICS IN A NATURAL PROGRAM FEEDLOT
Abstract
Effects of live yeast (Saccharomyces cerevisiae) fed to beef cattle
finishing diets on growth performance; apparent digestibility, carcass
characteristics, and feeding behavior were evaluated. Control (CTL), Low Yeast
(LY), and High Yeast (HY) steam-flaked corn-based finishing diets were fed to
steers (n = 144; 341 ± 52 kg) in a completely randomized block design. Animals
were kept in a natural program, in which technologies such as implants,
ionophores, and antibiotics were not utilized. Yeast was mixed with cottonseed
meal as a premix and included in the diet at a 1% DM basis. Data were analyzed
using the GLIMMIX procedures of SAS, and pen (n =12/treatment; 4 steers/pen)
represents the experimental unit. Feed efficiency tended to be improved (P =
0.08) between days 0 to 183 for the LY diet by 4.3% over other treatments. The
number of premium choice carcasses increased linearly (P < 0.01) with increasing
yeast inclusion in the diet at 33.3%, 68.8% and 70%, respectively. There was a
tendency (P = 0.09) for choice carcasses to be increased linearly with increasing
yeast levels in the diet. A quadratic response was shown for apparent digestibility,
in which steers fed LY had improved digestibility (P < 0.01) of dry matter by
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5.4%, organic matter by 4.8%, NDF by 15.2%, ADF by 20.2%, CP by 6.2%, and
EE by 2.5%. Intake of DM, ADG, and G:F carcass adjusted were not affected by
dietary treatments. Moderate inclusion of live yeast improved efficiency of
nutrient utilization and carcass characteristics of steers fed steam-flaked corn-
based finishing diets, which tended to positively affect gain efficiency on a live
basis.
Key words: behavior, cattle, digestibility, natural, yeast
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Introduction
Growth promoting technologies are utilized by the beef industry to reduce
health issues and improve growth performance during the growing and finishing
phase of feedlot cattle. However, despite the fact these technologies improve the
efficiency of the beef industry, public scrutiny is forcing the more judicious use of
these products. Because of this, natural options offer a premium to producers,
while potential improvement of gastrointestinal health and animal growth
performance can be expected, when compared to animals not fed such feed
technologies. Without the use of growth promoting technologies, efficiency
within the feedlot is reduced, thus the use of natural products to improve growth
is justified. Unfortunately, there is conflicting evidence about whether or not the
use of yeast in the diet improves growth performance, digestibility, and carcass
characteristics of cattle during the finishing phase fed steam-flaked corn-based
diets.
Yeast products included in the diet stimulate fiber-digesting bacteria and
improve digestibility of the nutrients consumed, which allows the animal to grow
more efficiently (Wiedmeier et al., 1987). Yeasts are used for more than just
growth performance; they are also used to improve health during stressful
situations and carcass quality (Hernandez-Garcia et al., 2015). While the impact
on growth performance has been inconsistent, the varying modes of action of
yeast in the diet and its impact on digestibility of nutrients have been well
documented. When yeast is supplemented in the diet, cellulolytic bacteria within
the rumen are stimulated and fiber digestion is improved (Hernandez-Garcia et
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al., 2015). The objective of this study was to determine if the supplementation of
yeast within the diet improved growth performance, digestibility of nutrients,
behavioral response to the diet, and carcass characteristics of finishing feedlot
cattle fed steam-flaked corn-based diets.
Materials and Methods
All experimental procedures involving the use of animals were done in
accordance with Texas Tech University Animal Care and Use Committee
Protocol 15044-05. The experiment was conducted at Texas Tech’s University
Burnett Center located in Idalou, TX.
Feedlot Growth Performance
On June 4th, 2015, 171 Black Angus cross steers arrived at Texas Tech
University Burnett Center. Cattle were weighed June 5, 2015, given vaccines for
Bovine Rhinotracheitis Virus, Parainfluenza 3-Respiratory syncytial vius,
mannheimia haemolytica, and pasteurella multocida vaccine at 2 ml/hd; a vaccine
for Mycoplasma bovia at 2 mL/hd; fenbendazole at 20mL/hd; clostridium
chauvoei-septicum-novyl-sordellii-perfringens types C&D bacterin-toxoid at 2
mL/hd; Vitamin E, A +D at 5 mL/hd; and ivermectin pour-on at 35 mL/hd. Steers
were separated into 16 receiving pens, and left for approximately two weeks to
recover from the initial processing and transport. During this period and days that
followed until the study started animals were limit fed (2% BW) with standard
receiving diet that included 18.6% steam-flaked corn, 15.23% cottonseed hulls,
and 63.26% sweet bran. On June 17, 2016, cattle were weighed again to sort into
12 blocks at 3 pens/block into 36 pens of four animals each. Cattle within blocks;
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were randomly allocated into Burnett Center pens (2.9 m wide × 5.5 m deep; 2.4
m of linear bunk space) on June 30, 2015. After a week of acclimation, animals
that had been previously allocated into respective experimental units were sorted
to reduce variation within block, and the experiment was initiated on July 8, 2015,
when initial BW was taken. At this moment, animals started on adaptation diets,
which already contained yeast treatments. Step-up diet 2 was fed for one week,
and included 28.43% steam-flaked corn, 7.19% cottonseed hulls, 41.13% sweet
bran, 15.17% corn silage, 4.99% sorghum silage, 1.05% limestone, 1.35%
supplement and 0.69% of each respective treatment. The step-up diet 3 was fed
for another 7d included 40.72% steam-flaked corn, 3.70 cottonseed hulls, 31.31%
sweet bran, 15.62% corn silage, 5.13% sorghum silage, 1.08% limestone, 1.39%
supplement, 0.33% urea and 0.72% inclusion of each respective premix. On d15,
the cattle were placed on the finishing diet which was fed for the rest of the study,
and is shown in Table 1.
Cattle were sorted into three treatment groups. Each block combined three
pens, and each treatment was randomly assigned to one of the three pens
(randomized complete block design). The three treatment groups were Control
(CTL), which included no yeast, Low Yeast (LY), which targeted for a yeast
intake of 25 g/hd/daily, and High Yeast (HY), which targeted for a yeast intake of
50 g/hd/daily. The yeast used was live yeast Saccharomyces Cerevisiae provided
by ABVista, United Kingdom. These treatments were administered via premixes
included at 1% in the diet on a DM basis. The diets and their nutritional
composition are shown in Table 1.
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All premixes were made at the Texas Tech University Burnett Center Feed
Mill in a ribbon type mixer (Marion Mixers Inc.) The premix included cottonseed
meal and yeast at increasing levels according to the treatment plan. Diet and
ingredient samples were taken once a week and tested for DM at 100°C forced-air
oven. Diet samples were also frozen from each week and a composite from each
period (35-d) was made throughout the entire study.
Unshrunk body weights were collected on day 0, 35, 70, 105, 140, 183 and
204 before daily feeding at 0630 on each of these days. Weights were taken using
a large pen scale (Cardinal Scale Manufacturing Co., Webb City, MO; accuracy ±
2.7 kg), except by day 0, 183, and 204, where individual BW were taken (Silencer
Chute, Moly Manufacturing, Lorraine, KS, mounted on Avery Weigh-Tronix load
cells, Fairmount, MN; readability ± 0.45 kg; before each use, the scale was
validated with 454 kg of certified weights). Collecting the orts and deducting it
from the total dietary DM offered to the pen each day calculated dry matter
intake. On the final day of the study, cattle were weighed individually and
shipped to Creekstone Packing Plant in Arkansas City, Kansas. Trained personnel
from West Texas A&M University took HCW and liver abscess data, and used
camera data to determine quality grade, yield grade, marbling score, LM area, and
backfat thickness at the 12th rib. Liver abscesses were classified using the methods
described by Brink et al. (1990). Dressing per cent was calculated using HCW
divided by the non-shrunk final BW, which was then used to calculated carcass-
adjusted BW from the HCW divided by the average DP from all three dietary
treatments and adjusting for 4% shrink (NRC, 1996). The carcass-adjusted
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weights were then used to determine carcass-adjusted ADG, final shrunk BW,
initial BW, and G:F. The interim weights were used to calculate ADG, and G: F
ratio for the steers during each period.
Apparent Total Tract Nutrient Digestibility
During days 110 to 116, a digestibility assessment of the feed was
conducted. On day 110 bunks were cleaned at 0700 before feeding, and feces
samples were collected at 1600 that evening. During referred days, ort samples
were collected at 0700 and subtracted from the previous day offered diet. Feces
were also collected from at least three steers within each pen at 0700 and 1600h.
Approximately 10% of the orts were kept for analyses. Diet samples were
collected for all three treatments when cattle were fed at 0900 (composite
representing each experimental unit). At the end of the week, fecal samples were
composited by pen (ten samples per pen), 200 grams from each bag were mixed,
dried and a subsample was frozen (-20°C) for analyses. A similar composite was
made for the diet samples and ort samples. Ort samples collected that were greater
than 5% of total offered were kept for nutrient analyses. All samples were dried
for 72 hours in a 55°C forced air oven. Samples were ground in a 1 mm screen
Wiley Mill (Thomas Scientific, Swedesboro, NJ) and analyzed in laboratory for
DM, ash, NDF, ADF, AIA, and CP. A commercial laboratory (Servi-Tech,
Amarillo, TX), analyzed all fecal, diet and ort samples for starch and EE. The
AIA was utilized as an internal market (Van Keulen and Young, 1977) to
determine total fecal output. When the orts exceeded 5% of the total amount fed
daily, the AIA for each quantity was adjusted.
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Laboratorial Analyses
Except for daily dietary sub-samples dried at 100°C, forced air oven for
24h (used to calculate DMI), all samples were pre-dehydrated at 55°C, forced air
oven for 72 h prior to analyses. Samples were ground through a 1-mm screen
(Wiley Mill; Thomas Scientific, Swedesboro, NJ) before nutrient analyses. Lab
analyses were adjusted to laboratorial dry matter (100°C for 24 hours) using
method 950.01 (AOAC, 1990). Organic matter was determined by subtracting the
residue from the ash process, which was processed oven (550°C for 4 hours)
following the method 942.05 (AOAC, 2005). Approximately 0.3 g of each diet,
fecal and ort sample, were placed into crucibles for N analysis (FP-200, Leco
Corporation, St. Joseph, MI) with the official method 992.15 (AOAC, 1995).
Neutral and acid detergent fibers were analyzed in sequence (Ankom 200,
Macedon, NY) where NDF procedure included thermo-stable amylase, sodium
sulfite and an acetone rinse (Van Soest et al., 1991). Starch and EE were analyzed
at a commercially certified laboratory (Servi-Tech, Amarillo-TX).
Feeding Behavior
On day 158-159, feeding behavior was analyzed for a 24h period.
Observations were recorded every 5 minutes, whether cattle were resting, active,
eating, ruminating, or drinking. Chewing activity was calculated by adding eating
and ruminating time. Because of the 24h period and 5-minute intervals, some data
points were missing due to human error (approximately 5%), so all behavior
results were expressed as daily percentage.
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Statistical Analysis
Data were analyzed using the GLIMMIX procedures of SAS (SAS Inst.,
Inc., Cary, NC) with pen considered the experimental unit in a randomized block
design. The fixed effects of treatment were evaluated for intake, behavioral
evaluation, apparent total tract nutrient digestibility, growth performance and
carcass characteristics, with random effect of pen. Least square mean differences
were adjusted with a Tukey’s test, and degree of freedom bias was adjusted using
Kenward Rogers. Carcass data (USDA Quality Grade and liver scores) and
feeding behavior were reported on an individual basis, and the same model was
used as described previously. The data was non-Gaussian, so the Link function
was used for the analysis of the treatment effects. Linear and quadratic responses
(0, 25, and 50 g DM of yeast daily) and contrasts were evaluated. The two harvest
groups were considered a random effect. Significant differences were considered
if P ≤ 0.05 and tendencies if P > 0.05 and ≤ 0.10.
Results
Treatment Data
Throughout the course of the experiment, cattle were treated for both
lameness and respiratory issues. Two steers from the CTL treatment and one from
the LY treatment were removed early in the trial due to lameness. Another steer
was removed from the CTL treatment due to kidney failure. Respiratory disease
also hurt the feedlot, and seven were removed from the CTL group, 9 from the
LY treatment, and 10 from the HY treatment and were treated for respiratory
illness and removed from the study. Of the remaining steers, one from the HY, 3
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from the LY and 3 from the CTL group were treated for respiratory issues and
remained in the experiment and were slaughtered at a local abattoir.
Growth Performance, Carcass Characteristics and Feeding Behavior
Growth performance, ADG, and G:F were not different between all three
treatments, shown in Table 2. There was a tendency (P = 0.08) for G:F to be
improved quadratically during the period of d0-183, and from d0-105 (P = 0.10)
for the LY treatment compared to the CTL and HY treatments.
Carcass characteristics and quality are noted in tables 3 and 4,
respectively. When evaluating carcass characteristics, similar to growth
performance, differences were not noted (P > 0.27). Between the three treatments,
no differences (P > 0.27) were noted in HCW (377 kg), dressing percent (63%),
yield grades (3.55), KPH percentage (2.02), marbling score (59), rib-eye area
(88.41 cm2), and backfat thickness (19 mm), as shown in Table 3. Although no
differences were observed in carcass characteristics, the inclusion of yeast in the
diet did result in some differences in carcass quality. There were no differences (P
= 0.11) in the amount of Prime carcasses in each treatment; however, Premium
Choice carcasses were increased linearly (P < 0.01) with increasing levels of yeast
in the diet. The CTL treatment had 33%, LY had 69%, and HY had 70% Premium
Choice carcasses. Choice carcasses decreased linearly (P = 0.05), where the CTL
had 34% Choice carcasses, while LY had 11% and HY had 9% Choice carcasses.
This shows the inclusion of yeast in the diet affects carcass quality, and using
yeast increases the number of carcasses produced that are of a high quality.
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Liver score data for A-minus livers are showcased in Table 5. There were
very few carcasses with liver abscesses in the entire experiment, and there were
no differences between treatments as to which had more A minus scored livers.
The CTL group had 5 contaminated livers, and 2 A minus livers, the LY treatment
had 3 contaminated livers, 1 A plus, and 1 A minus liver, and the HY treatment
had 3 contaminated carcasses, and 4 A minus carcasses.
Feeding behavior is outlined in Table 6. No differences were noted
between treatments in terms of ruminating (P = 0.28), eating (P = 0.51), drinking
(P = 0.70), resting (P = 0.48) and chewing (P = 0.56) activity, which was a
combination of rumination and eating times. Cattle spent on average 8-9% of their
time eating, 10-12% ruminating, and 78-79% resting.
Apparent Total Tract Nutrient Digestibility
Apparent total tract digestibility was summarized in Figures 1 and 2. Other
than starch (P = 0.55), all nutrients experienced quadratic improvement (P < 0.01)
for the LY treatment over CTL and HY treatments. Although LY had greater
apparent total tract nutrient digestibility compared to both HY and CTL, HY also
had greater total apparent tract digestibility of all nutrients except for starch and
ether extract over the CTL treatment. In the fiber fractions, there was a quadratic
response for NDF to be improved over CTL and HY treatments (P < 0.01), and a
significant improvement (P < 0.01) of either yeast treatment compared to the CTL
treatment.
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Discussion
The objective of this experiment was to evaluate levels of yeast and its
effect on the growth performance, carcass characteristics, apparent total tract
digestibility and feeding behavior of steers fed steam-flaked corn-based finishing
diets. The inclusion of yeast in the diet improved apparent total tract nutrient
digestibility of the steers, without causing a significant effect on growth
performance. A trend (P = 0.10) was observed in feed efficiency of the steers
from d0-183 fed the LY treatment. Although not statistically significant, the LY
treatment numerically improved growth performance during all periods of the
study. It would be expected LY had improved growth performance, because there
was improved digestibility of all nutrients but starch, which indicates cattle
derived more energy from the diet which could potentially improve growth
performance. The improved digestibility does not directly translate to improved
growth performance; the energy derived from the diet can become lean tissue or
fat tissue in marbling and back fat thickness. The use of yeast in the diet may
cause more marbling and fat deposition, which was observed in cattle receiving
higher carcass quality (P = 0.01) with increasing levels of yeast in the diet.
The moderate inclusion of yeast in the diet of beef steers fed steam-flaked
corn-based finishing diets numerically improved their feed efficiency. Other
studies observed similar results when yeast was included in the diet when cattle
were under stressful conditions (Cole et al., 1992, and Philips and VonTungeln
1985). Yeast and other DFM have been used as tools to improve the establishment
of intestinal microflora in young, stressed ruminants, improving the digestibility
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of the diet (McAllister et al., 2011). Once it was observed DFM reduced the risk
of acidosis in ruminants, their use and continued research has been used to
improve cattle growth performance, specifically in natural programs.
The improved digestibility of nutrients in the current trial, specifically the
fiber fraction was consistent with other studies. In a review by McAllister et al.
(2011), it was reported the reason yeast improves fiber digestion by improving
cellulolytic bacterial growth, while simultaneously reducing the risk for acidosis
of feedlot cattle. Similarly, in this study, fiber fraction digestibility (Figure 2) was
significantly improved by moderate inclusions of yeast in the diet. As explained
by Jouany et al. (1998), yeast potentially provides an improved environment for
cellulolytic bacteria because it reduces the oxygen load in the rumen, improving
the environment for those microbes to grow and digest fiber fractions. This
improvement in fiber digestibility was observed by improved growth performance
for the moderate yeast level inclusions as well, albeit there was only a tendency
for improved growth in the current study
The improvement in CP digestibility is consistent with studies conducted
by Erasmus et al. (1992) and Dawson (1991), which observed improved ammonia
uptake with yeast inclusion in the diet. Improved CP digestibility may have been
due to improved microbial efficiency, with ammonia uptake to grow microbial
protein and activity (Erasmus et al., 1992). This improvement could improve
microbial protein production, ultimately increasing the protein and thus, amino
acids, available to the animal to use in production responses. However, in the
current study, LY treatment cattle had improved digestibility over HY treatment,
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which is in contrast to other studies that conclude increasing levels of yeast
improved growth performance. The digestibility data is supported by the
numerical and tendency in gain efficiency improvements for LY steers over HY
and CTL steers. In most cases, the HY treatment was better than the CTL
treatment in terms of nutrient digestibility. The LY treatment might have been the
threshold for improved performance for yeast in the rumen environment, and
increasing past those levels has no benefit.
In a study by Yoon and Stern (1995), the inclusion of yeast in the diet of
dairy calves from 1% to 2% did not statistically increase the DMI from 6.2 to 6.4
kg daily, while the control diet only ate 5.6 kg daily. Similar to the current
experiment, there appeared to be a threshold at which the diet was the most
efficient. In a study by Swyers et al. (2014) included a Saccharomyces cerevisiae
fermentation product in a high concentrate diet (> 50% steam-flaked corn) at 2.8
g/head daily and observed the number of carcasses that grade USDA Choice, but
also observed a decreased ADG compared to Monensin treated animals. In a
study by Hinman et al (1998), the researchers included a Saccharomyces
cerevisiae fermentation product in a barley and potato residue finishing diet at 85
g/head daily for the first 28 days, and 28 g/head daily for the final 85 days of the
trial, and it improved steer ADG by 6.9% and feed efficiency by 4.5% throughout
the trial. In a dairy trial, Kung et al. (1997), cattle were fed diets including a
Saccharomyces cerevisiae product at 0, 10, and 20 g inclusion per head daily.
They observed cattle in the control group produced 36.4 kg of milk/day, and milk
production was 39.3 and 38.0 kg/d from the 10 and 20 g of yeast/day steers,
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respectively (Kung et al., 1997). Similar to the current study, there appeared to be
a threshold at which the yeast was effective in the diet. In a study by Miller-
Webster et al. (2002), they compared two yeast products from two different
companies against a control diet, and discovered one of the yeasts left the rumen
at a higher pH average and higher microbial N/kg of dry matter digestibility. In a
study by Martin and Nisbet (1992) comparing two yeast strains, Asperigillus
oryzae and Saccharomyces cerevisiae, they observed improve total volatile fatty
acids and cell yield within the rumen. In this review by Martin and Nisbet (1992),
they were unable to determine if one treatment was more beneficial than the other
and that more research was needed, they were able to conclude improved
cellulolytic bacteria production for improved fiber digestion was a common factor
of the two DFM.
The lack of differences between the treatments when observing the
feeding behavior of the steers yeast showed yeast affects more digestive tract
kinetics rather than behavior. When cattle spend more time eating and ruminating,
they produce more saliva, which acts as a buffer in the rumen and reduces the risk
of acidosis, providing a better rumen environment for microbes. When improved
nutrient digestibility were observed in the current study, it was initially
hypothesized some of the results may have been due to increased chewing, which
can be related to a decrease in particles while providing more buffering solution.
However, when behavioral intakes were analyzed no differences were noted
between the three treatments. If there were to be differences in feeding behavior,
it might have similar effects to the product monensin, which is also included in
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the diets at low levels while modifying the ruminal environment. In a review by
Gonzalez et al. (2012), monensin reduces meal size and frequency of meals,
reducing the starch load within the rumen, increasing ruminal pH averages. No
results such as this on feeding behavior were observed in the current study, which
might suggest yeast does not have the same modifying effects on the behavior of
cattle such as monensin, despite the fact both work by modifying the ruminal
environment.
Although the current study did not evaluate steer immune response or
growth response while under periods of stress, with improved digestibility
observed in the current study, animal might be able to derive energy more readily
during periods of stress because of improved ruminal environment. This
improvement in energy intake may help cattle overcome stressful periods and
improve better, not only during stressful phases of their lives, but also during the
subsequent finishing performance.
Natural program steers do not have the propensity to perform compared to
steers fed in conventional feeding programs as outlined by Wileman et al. (2014).
However, with the increased consumer concern as mentioned previously, having a
good knowledge on products considered available for natural production and their
methods of action would be beneficial for the beef industry. If a product is found
to improve performance naturally, it can be used as an alternative. While there are
doubts these products will ever work to the same efficiency as current growth
promoting technologies, any improvements over none at all are a benefit. The
current study had the tendency to improve gain efficiency while improving (P <
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0.01) apparent total tract nutrient digestibility for all nutrients except starch (P =
0.55). The current study did not compare to conventional production methods,
however, feeding yeast at 25 g/head daily was better than not including yeast at
all in the diet. Similar to the current study, Moloney and Drennan (1994) observed
a tendency for improved gain efficiency in steers with no affect on carcass
characteristics. They came to the conclusion that yeast dietary interactions would
need to be further researched before making recommendations for the industry. In
steam-flaked corn-based finishing diets, the optimal inclusion of Saccharomyces
cerevisiae was 25 g/head daily.
Carcass characteristics were improved (P < 0.01) with increasing levels of
yeast on the number of Premium Choice carcasses produced. Carcass quality is
measured by rib-eye area, marbling, and appearance of the meat. An increase in
marbling and improvement in carcass quality may come from improved fat
deposition due to the improved fiber digestibility. Similar to the current study,
Swyers et al. (2014) observed an improvement in carcass quality with the
inclusion of Saccharomyces Cerevisiae fermentation product included in a steam-
flaked corn based finishing diet. It was also observed no difference between the
yeast and control diet in that study as well (Swyers et al., 2014). Other studies that
compared the inclusion of yeast to control diets experienced similar results with
no differences in carcass characteristics between treatments (Zerby et al., 2011).
Swyers et al (2014) hypothesized the inclusion of yeast coupled with the
improved quality grade of steers suggests cattle fed a yeast product are finished at
a lower end weight than monensin fed steers, resulting in fewer days on feed. This
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was observed in the current study, with similar back fat thickness and marbling,
but improved quality as the yeast levels were increased. Although we did not
measure ruminal VFA concentrations, we can speculate yeast changed the
ruminal environment, to affect the carcass quality to improve carcass quality.
According to Smith and Crouse (1984), acetate supplies 70-80% of the acetyl
units for subcutaneous fat, while only supplying 10-25% in intramuscular adipose
tissue. Glucose, which is made in the liver from propionate, supplies 1-10% of the
acetyl for subcutaneous fat, while supplying 50-75% for the intramuscular or
marbling fat (Smith and Crouse, 1984). Including yeast in the diet could be the
reason for improved carcass characteristics due to the improved fiber digestibility,
as potentially more acetic acid could be converted to fatty acids.
Implications
In the diets of natural program steers fed steam-flaked corn-based
finishing diets, yeast improved overall apparent total tract nutrient digestibility,
which could potentially improve growth performance as compared to steers not
fed yeast products, although such expectation was not observed in the current
study. While growth performance results have been inconsistent, it is evident that
yeast does affect digestion. This coupled with data that suggests yeast improves
animal growth performance during periods of stress, might indicate cattle who
have been recently introduced to the feedlot could improve. Beneficial effect the
LY treatment had on apparent total tract nutrient digestibility of fiber leads an
inquiry about how it would affect the digestion of poorly digestible roughages
used during the adaptation phase of the feedlot phase. If yeast were to improve the
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digestion of fibers from low roughage sources, cattle would be able to derive
more energy from these sources, and this supplementation could improve feedlot
profitability as they use less expensive roughage sources apart from alfalfa hay,
which is included in traditional adaptation phases. In conclusion, yeast
supplementation in the diets of beef steers improved nutrient digestibility at
moderate inclusions, but also positively affected carcass characteristics with
increasing yeast levels, while not negatively affecting growth performance.
Depending on the economics of carcass at the time of retail, it may be beneficial
for producers to include higher levels of yeast in the diet to improve carcass
quality and thus premiums for top-grade carcasses.
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Table 1. Dietaryingredientsandnutritionalcompositionofdietsfedtonaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.
Item Live yeast, g/steer daily
0 25 50 Inclusion, % DM basis
Corn grain, Steam flaked
62.35 62.35 62.35
Sweet Bran 20.00 20.00 20.00 Corn Silage 10.00 10.00 10.00 Sorghum Silage 2.50 2.50 2.50 Supplement 2.00 2.00 2.00 Limestone 1.65 1.65 1.65 Urea 0.50 0.50 0.50 ABVista Premix Control
1.00 - -
ABVista Premix Low - 1.00 - ABVista Premix High - - 1.00
Analyzed Nutritional Composition NEm, Mcal/kg1 1.96 1.98 1.96 NEg, Mcal/kg1 1.32 1.32 1.30 CP, % DM 14.71 14.58 14.94 NDF, % DM 16.39 19.60 19.79 ADF, % DM 5.80 6.14 6.63 EE, % DM 3.00 3.40 3.20 Starch, % DM 49.60 47.30 48.40 1Calculated from growth performance data
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Table 2. Effects of ABVista yeast (Saccharomyces cerevisiae) on growth performance of natural program beef steers fed a steam-flaked corn-based finishing diet.
Item Live yeast, g/steer
daily SEM1 P-Values
0 25 50 L2 Q3 Contrast Initial BW adj, kg 342 341 342 7.03 0.80 0.56 0.61 Final BW adj, kg 574 578 574 12.56 1.00 0.67 0.83 ADG, kg
Day 0-35 1.57 1.67 1.66 0.062 0.25 0.43 0.17 Day 0-70 1.44 1.49 1.44 0.047 0.97 0.37 0.63 Day 0-105 1.46 1.51 1.49 0.039 0.54 0.35 0.32 Day 0-140 1.34 1.34 1.36 0.039 0.81 0.76 0.96 Day 0-183 1.32 1.35 1.29 0.041 0.60 0.37 0.99 Day 0-End 1.19 1.21 1.18 0.033 0.76 0.49 0.93 Carcass Adj. 0-End4 1.18 1.20 1.19 0.036 0.89 0.65 0.73
DMI, kg/d
Day 0-35 7.42 7.46 7.48 0.064 0.46 0.89 0.48 Day 0-70 7.90 7.97 7.91 0.093 0.95 0.60 0.75 Day 0-105 8.31 8.28 8.33 0.093 0.84 0.77 0.98 Day 0-140 8.27 8.22 8.42 0.122 0.30 0.29 0.71 Day 0-183 8.36 8.32 8.50 0.255 0.44 0.46 0.76 Day 0-End 8.46 8.39 8.48 0.239 0.92 0.61 0.86
Gain:Feed Live Basis 0-35 0.211 0.224 0.222 0.008 0.29 0.38 0.18 Live Basis 0-70 0.182 0.187 0.181 0.005 0.90 0.34 0.70 Live Basis 0-105 0.176 0.183 0.178 0.004 0.53 0.10 0.18 Live Basis 0-140 0.163 0.163 0.160 0.004 0.62 0.74 0.79 Live Basis 0-183 0.158 0.163 0.152 0.004 0.20 0.08 0.81 Live Basis 0-End 0.141 0.144 0.139 0.003 0.58 0.17 0.83 Carcass Adj. 0-End4 0.139 0.143 0.140 0.003 0.93 0.33 0.57
1Standard error of the mean. 2Linear P-value 3Quadratic P-value 4Carcass-adjusted ADG and G:F from carcass-adjusted final shrunk BW, initial adjusted BW, and days on feed.
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Table 3. EffectsofABVistayeast(Saccharomycescerevisiae)oncarcasscharacteristicsofnaturalprogramsteersfedasteam-flakedcorn-baseddiet.
Item Yeast Treatment, g /steer
daily SEM1 P-Values
0 25 50 L2 Q3 Contrast Hot carcass weight, kg
376.4 378.7 376.4 5.34 0.99 0.67 0.83
Dressing percentage4
62.90 62.83 63.31 0.314 0.33 0.46 0.63
Yield grade 3.66 3.44 3.55 0.125 0.56 0.30 0.31 KPH Percent 2.02 2.02 2.02 0.023 0.80 0.89 0.77 Marbling score5 59.08 57.97 60.65 2.013 0.59 0.45 0.93 Rib-eye area, cm2 87.81 89.03 88.39 1.445 0.79 0.59 0.83 Back-fat thickness, mm 19.76 18.17 19.07 0.907 0.59 0.27 0.47 1Standard error of the mean 2Linear p values 3Quadratic p values 4Dressing percent calculated using non-shrunk final BW/HCW 530 = slight, 40 = small, 50 = modest, 60 = moderate, 70 = slightly abundant
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Table 4. EffectsofABVistayeast(Saccharomycescerevisiae)oncarcassqualityofnaturalprogrambeefsteersfedasteam-flakedcorn-basedfinishingdiet.
Item Yeast Treatment, g/steer daily
SEM1 P - Values
0 25 50 L2 Q3 Contrast Carcass Quality
Prime 27.72 11.23 18.91 0.077 0.37 0.15 0.11 Premium Choice 33.34 68.77 70.49 0.081 < 0.01 0.12 < 0.01 Choice 33.77 11.28 8.86 0.116 0.05 0.45 0.03 1Standard error of the mean 2Linear P-value 3Quadratic P-values
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Table 5. EffectsofABVistayeast(Saccharomycescerevisiae)onliverscoresofnaturalprogrambeefsteersfedsteam-flakedcorn-basedfinishingdiets.
Item Yeast Treatment
g/steer daily SEM1 P - Values
0 25 50 L2 Q3 Contrast A Minus 1.60 0.63 3.29 0.027 0.50 0.28 0.92 Total4 2 2 4 - - - - A-Plus4 0 1 0 - - - - A4 0 0 0 - - - - Others-Contaminated4
5 3 3 - - - -
1Standard error of the mean 2Linear P - values 3Quadratic P – values 4No statistical estimate due to data not being able to converge. Not enough liver abscesses to determine a difference
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Table 6. EffectsofABVistayeast(Saccharomycescerevisiae)onfeedingbehaviorofnaturalprogrambeefsteersfedsteam-flakedcorn-basedfinishingdiets.
Item Yeast Treatment, g/steer
daily SEM1 P -Values
0 25 50 L2 Q3 Contrast Time, % of 24
hours
Eating 8.47 8.32 9.04 0.652 0.51 0.55 0.78 Ruminating 11.51 11.67 10.27 0.958 0.28 0.43 0.58 Chewing 20.18 20.35 19.44 1.116 0.56 0.63 0.80 Resting 79.34 79.24 77.97 1.594 0.48 0.73 0.66 Drinking 0.25 0.29 0.28 0.059 0.70 0.68 0.60 Active 0.51 0.41 0.38 0.123 0.02 0.79 0.03 1Standard error of the mean 2Linear P - values 3Quadratic P - values
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Figure 1. Effects of ABVista yeast (Saccharomyces cerevisiae) on apparent total tract nutrient digestibility of natural program beef steers fed steam-flaked corn-based finishing diets.
c cc
ba a
a
a
b bb
b
0
20
40
60
80
100
120
DryMatter OrganicMatter Starch CP EE
ApparentTotalTractDigestibility,%
Nutrient
0 25 50
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Figure 2. Effects of ABVista yeast (Saccharomyces cerevisiae) on apparent total tract fiber fraction digestibility of natural program beef steers fed a steam-flaked corn-based finishing diet.
c
c
ba
a
a
bb
b
0102030405060708090100
NDF ADF Hemicellulose
ApparentTotalTractDigestibility,%
FiberFraction
0 25 50
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CHAPTER III
COTTON BURRS AS ALTERNATIVE ROUGHAGE TO ADAPT BEEF STEERS TO STEAM-FLAKED CORN-BASED FINISHER DIETS
Abstract
Effect of cotton burrs as a roughage source during the transition of beef
cattle (hay to finisher diet) was evaluated on intake, ruminal characteristics,
nutrient digestibility, and feeding behavior. Ruminally cannulated steers (n = 6;
BW = 235 ± 81 kg) were assigned using a complete randomized design to 1 of 2
adaptation strategies: Alfalfa hay-based or cotton burrs-based. In both strategies,
roughage sources decreased as steam-flaked corn gradually increased. Steers were
fed ad libitum once daily, a series of six diets (7-d period each): wheat hay; 4
step-ups; and a finisher. In situ technique was used to assess ruminal fiber
degradability (substrate = wheat hay). Wireless rumen pH probes were used. A 3-
d spot fecal collection (twice daily, last 3 d of each period) and AIA were used to
estimate apparent total tract nutrient digestibility. Rumen fluid samples (0, 4, 8,
and 16 h after feeding) were taken (d-6 of each period) for VFA and NH3. Prior to
the adaptation strategies start, animals were fed add libitum wheat hay. Data were
analyzed using Glimmix procedure of SAS (wheat hay period used as a
covariate). Intake was not affected by adaptation strategies (P ≥ 0.16), except for
a tendency (P = 0.10) for steers adapted with alfalfa-strategy to ruminate more per
kg of NDF consumed during finisher diet, than those adapted with cotton burrs-
strategy. Steers fed cotton burrs-strategy showed lower ruminal pH average on
step-3 and finisher periods (5.62 and 5.51 vs. 6.04 and 5.83; P < 0.01 and P =
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0.05, respectively) compared with alfalfa-strategy. A greater area of pH below
5.60 (200 vs. 15 min*pH; P < 0.01); lower ruminal NH3 concentration (5.1 vs. 8.8
mg/L; P < 0.01); and lower digestibility (OM, ADF, and hemicellulose; P ≤ 0.02)
during step-3 were also observed for steers fed cotton burrs-strategy compared to
alfalfa-strategy, respectively. However, cotton burrs-strategy steers showed
greater (P = 0.01) NDF digestibility during step-4; greater (P < 0.01) OM
digestibility during finisher diet; and lower acetate/propionate ratio (P = 0.04)
with a tendency (P = 0.08) to have greater propionate molar proportion during
step-2, compared to alfalfa-strategy steers. Ruminal fiber degradability was not
affected by adaptation strategies (P ≥ 0.36), neither was dietary starch
digestibility during common finisher (P = 0.73). Cotton burrs adaptation strategy
induced an improved ruminal fermentation environment during finisher diet,
although with riskier ruminal pH and rumination than alfalfa-strategy. Further
evaluation must consider cattle growth performance and economic aspects.
Key words: adaptation, alfalfa, cotton burrs, metabolism
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Introduction
The period during which cattle are adapted from high roughage to high
concentrate diets is extremely important on their performance throughout the
finishing phase. The adaptation period can be extremely costly for the feedlot as
the usage of roughages, which have a low energy density, is extremely high,
accounting for approximately 50% of the total roughage consumed during the
feedlot phase (Mader et al., 1993). Because roughages are costly, reducing
reliance on them during the adaptation phase would be ideal. There are a few
available options to decrease dependence on roughages during the adaptation
phase. One option would be to decrease the days spent in the adaptation phase,
decreasing the time spent adapting to high concentrate diet, which could increase
the risk for acidosis as the rumen is abruptly exposed to high starch loads.
Another option feedlots have to reduce costs during the adaptation period is to use
byproducts from industries that utilize plant and plant products for their energy or
main product, often leaving a high fiber, low starch product behind. These
products have reduced cost because the main product was utilized, reducing costs
for the feedlot. However, the adaptation phase requires a low-starch fibrous
product to induce the ruminal microbial population acclimation from low to high
starch diet. The issue with using these byproducts is their effect on subsequent
performance and physiological response of the animals to the byproduct itself.
Some byproducts already widely used in the beef industry component of
adaptation strategies are wet corn gluten feed. A byproduct that has not been
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widely researched in areas with high cotton production is cotton burrs, which are
the byproduct after the cotton milling process. The resultant product is high in
fiber, making it an ideal product for feedlots to use in place of expensive
roughage sources such as alfalfa hay. Unfortunately, it has not been widely
researched in the adaptation phase, rather usually used for maintenance cow diets.
The objective of this study was to research the use of cotton burrs as the roughage
source in adaptation diets in the feedlot and their effect on ruminal metabolic
variables of growing beef steers as they adapted to high concentrate diets.
Materials and Methods
All experimental procedures involving the use of animals were done in
accordance with Texas Tech University Animal Care and Use Committee
Protocol (T13079). The study was conducted at Texas Tech University Burnett
Center, located in Idalou, TX.
Treatments, design, and feeding
Six ruminally cannulated beef steers (235 ± 81 kg) were assigned to one of
two adaptation strategies using a complete randomized design. The two strategies
were either alfalfa hay or cotton burrs-based. The experiment consisted of six
periods of 7 d each, and each period consisted of increasing levels of steam-flaked
corn and decreasing levels of the respective roughage source. The first period was
a common wheat hay diet, the next four step-up diets, and a common finishing
diet, outlined in Table 7, and analyzed nutritional composition outline in Table 8.
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Steers were fed ad libitum during each period, once daily at 1000 h. Steers were
housed individually in cement-slatted pens at the Texas Tech University Burnett
Center Pens. Each pen was equipped with automatic water troughs and individual
bunks.
Ruminal pH, VFA, and Ammonia Concentrations
On d-1 of each period, ruminal pH probes (DASCOR, Escondido, CA)
were calibrated in solutions of pH of 4.00 and 7.00, and adjusted to record
ruminal pH measurements every 6 minutes. Probes remained in the rumen
throughout each period and were removed at the end of d 7 of each period,
downloaded, recalibrated and reintroduced to the rumen for d 1 of each period,
prior to the daily feeding. This was repeated for all six periods. On d 7 of each
period, ruminal fluid was collected via the rumen cannulas and filtered through 4
layers of cheese-cloth, at 4, 8, 16, and 24 hours after feeding. All rumen samples
were immediately stored at -20°C for VFA and Ammonia analysis at a later date.
In order to analyze VFA from the ruminal fluid, samples were thawed and
centrifuged (10,000 ɡ; 10 min; 4oC). Four mL of the supernatant was treated
(deproteinized) with 0.8 mL of 25% metaphosphoric acid containing 2-
ethylbutyrate (0.2005 g in 100 mL; internal standard) (Erwin et al., 1961).
Individual VFA were analyzed in duplicate via gas chromatography (Shimadzu
GC-14A gas chromatograph).
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Ammonia analysis was performed using a hypochlorite assay for
ammonia. Excess supernatant from the thawed VFA samples was mixed with 2.5
mL of phenol reagents and 2.0 ml of hypochlorite reagent. They were heated in a
water bath at 95°C for 5 minutes. They were then analyzed in a spectrometer
(Shimadzu UV-1800 Spectrophotometer) to analyze for ammonia in the rumen
samples.
Apparent Total Tract Nutrient Digestibility
Spot fecal collection occurred twice daily during the final 3 days of each
period. Acid insoluble ash (AIA) was the internal marker utilized to determine
digestibility of nutrients (Van Keulen and Young, 1977), by analyzing the AIA in
both the diets and feces to estimate total fecal output. When orts were greater than
5% of total offered, the concentration of AIA was adjusted for AIA concentration
in the orts. All samples, diets, orts, and feces were kept under refrigeration (-
20°C) until they could be analyzed for their respective nutrients. Frozen samples
were thawed, dried at 55°C in a forced-air oven, for 72 hours. Samples were then
ground in a Wiley Mill (Thomas Scientific, Swedesboro, NJ) to pass through a 1
mm screen.
Laboratorial Analyses
Daily dietary sub-samples were dried at 100°C in a forced-air oven for 24
h, to adjust for dry matter intake. All samples to be used in laboratory analysis
were pre-dehydrated at 55oC in a forced air oven for 48 to 72 h prior to analyses.
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To correct for laboratorial dry matter, samples were dried at 100oC for 24 hours to
yield all nutrient values on a dry matter basis (method 950.01, AOAC, 1996). All
samples were ground through a 1-mm screen (Wiley Mill: Thomas Scientific,
Swedesboro, NJ) before laboratory nutrient analysis, except for in situ samples.
Neutral and acid detergent fiber fractions were analyzed in sequence, where NDF
was evaluated using thermo-stable amylase, sodium sulphite, final rinsing with
acetone, and subtracting remaining ash from residue (Van Soest et al., 1991). Ash
fractions were determined by ashing samples at 550°C in a furnace oven (4 h),
and organic matter was determined by subtracting from dry sample (method
942.05, AOAC, 1996). Nitrogen was analyzed by placing 0.3 g of each sample
into crucibles and run through LECO equipment (FP-200, Leco Corporation, St.
Joseph) (method 992.15, AOAC, 1995). Starch and ether extract were both
determined in a commercial certified laboratory (Servi-Tech, Amarillo, TX).
Ruminal In Situ Wheat Hay Degradability
Wheat hay collected from the same wheat hay diet fed to cattle during the
wheat hay period was used to accomplish ruminal fiber degradability evaluation.
Wheat hay samples were homogenized and ground in a Wiley mill (Thomas
Scientific, Swedesboro, NJ) to pass through a 2 mm screen. Approximately 5 g of
wheat hay was placed into separate triplicate nylon bags (10 x 20 cm: pore size 28
µm; Ankom Technology Co., Fairport, NY). The bags were placed into the rumen
via the cannula in reverse sequence at 0, 12, 24, and 48 hours post-feeding. Bags
were placed in the rumen d-6 through d-7 of each period and all removed at 0
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hours. After removing from the rumen, all nylon bags were washed in the lab
(Food Technology building) by running under tap water until the water ran clear.
Following rinsing, nylon in situ bags were dried at 50ºC in a forced-air oven for
72 h. The residue in each nylon bag was analysed for dry matter (100oC in a
forced-air oven for 4 h), organic matter (ash oven, 550oC, for 4 h), neutral
detergent fiber, and acid detergent fiber (analyzed in sequence) as described prior
in the laboratorial analysis section. Apparent disappearances of dry matter,
organic matter, NDF, and ADF were calculated using the following equation:
Disappearance, % = {1-[(residue, g × nutrient % in residue) / (sample, g ×
nutrient % in sample)]} × 100.
Feeding Behavior
On d 4 to 5 of each period, a 24h behavior of each animal was conducted.
Visual observations by trained personnel were taken every 5 minutes for the
following behaviors: eating, drinking, resting while standing up or laying down,
ruminating while standing up or laying down and active. From this total chewing
time, which was time spent eating plus time spent ruminating, total resting time,
which was time spent resting while standing up and laying down, and total time
spent chewing and ruminating per unit of NDF intake in the diet were also
calculated. Time spent on each activity was shown as a percentage for each day.
The intake of NDF was corrected for orts nutrient composition.
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Statistical Analyses
Data were analyzed using the GLIMMIX procedures of SAS. The initial
wheat hay period was used as a covariate for all variables. The effects of cotton
burrs versus alfalfa hay based adaptation strategies were evaluated for intake,
feeding behavior, apparent total tract nutrient digestibility, ruminal pH and VFA
variables, and ammonia concentrations in the rumen. For intake measures, day
was treated as a repeated measure. For ruminal VFA, ammonia concentration and
pH, time of day was treated as a repeated measure. Covariance structures for
repeated measures were chosen based on smallest Akaike’s information criterion
and Bayesian information criterion. The general degrees of freedom procedure
Kenward-Rogers was used to adjust for any bias on standard errors caused by
multiple terms in the random statement. Models included the random effect of
steer within treatment. Significant differences were considered if P ≤ 0.05 and
tendencies if 0.05 < P ≤ 0.10.
Results
Dry Matter Intake
The DMI was evaluated daily for each steer. The intake in kg/day was
evaluated for all six periods. No differences were noted between the two
strategies for all six periods (Table 9).
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Ruminal pH, VFA, and Ammonia Concentration
The averages of ruminal pH during the six period and the respective pH
variables are shown in Tables 9, 10 and Figure 3. The ammonia concentrations
observed within the rumen are found in tables 9, 10, and Figure 4. The cotton
burrs strategy had lower ruminal pH averages during steps 2 (P = 0.01), step 3 (P
< 0.01), and finisher diet (P = 0.05), with averages of 5.66, 5.62 and 5.51 vs 5.78,
6.04, and 5.83, respectively. Despite the fact rumen pH average was lower for the
cotton burrs strategy for steps 2, 3, and the finisher diet, the time and area spent
below pH 5.60, which is considered to be sub-acute acidosis, only during step 3
did the cotton burrs strategy spend more time below 5.60, as shown in Table 10.
During step 3, cattle spent 599 min/d under the pH of 5.60 compared to 160 min/d
in the alfalfa hay strategy. The area spent below 5.60 was also significant in step 3
(P < 0.01) for the cotton burrs strategy compared to the alfalfa hay strategy (200
min*pH vs 15 min*pH respectively). There was a tendency (P = 0.07) during the
finisher step that cotton burrs adapted cattle spent more time below a rumen pH of
5.0, 119 min/d vs. 5 min/d, compared to alfalfa hay-strategy cattle. Maximum
ruminal pH was greater (P = 0.05) during the finishing phase for alfalfa over the
cotton burrs strategy. Other ruminal pH variables such as maximum pH,
minimum pH and pH variance were not different between the treatments.
Ammonia concentrations were lower in steps 1 (P = 0.02) at 11.27 vs 18.74
(mg/L), and step-3 (P < 0.01) at 5.06 vs. 8.82 (mg/L) for the cotton burrs strategy
compared to alfalfa hay strategy, respectively. There was a tendency (P = 0.10)
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during step-4 for cotton burrs strategy to show have a lower ammonia
concentration (5.00 vs 6.75 mg/L).
Ruminal VFA molar proportion results are shown in tables 11 and 12,
showcasing wheat hay through to the finishing phase for acetate: propionate ratio,
acetate, propionate, butyrate, and total VFA in mmol/L observed in the rumen at
proportion of VFA in the rumen at mmol/100 mmol of the total VFA. In step 1,
molar propionate proportions were greater (P = 0.03) for alfalfa versus cotton
burrs strategy (23 versus 20.19 mmol/100 mmol). Isobutyrate molar proportions
were greater (P < 0.01) for alfalfa hay strategy (0.81 vs 0.49 mmol/100mmol)
over the cotton burrs strategy. During step 2, the acetate to propionate ratio had a
tendency (P = 0.09) to be greater for alfalfa at 1.76 vs. 1.35 for the cotton burrs
strategy. Propionate molar proportions were lower (P = 0.08) for the alfalfa hay
strategy at step 2 (29.41 vs. 34.90 mmol/100mmol). Isobutyrate molar proportions
had a tendency to be lower (P = 0.09) during step 2 (0.42 vs 0.54 mmol/100
mmol). During step 4, valerate molar proportions were lower (P = 0.04) for the
alfalfa hay strategy (1.52 vs. 2.39 mmol/100 mmol) compared to the cotton burrs
strategy. This continued during the finishing phase (P = 0.03) at 1.50-mmol/100
mmol during the alfalfa hay strategy versus 2.77 mmol/100 mmol for the cotton
burrs strategy.
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Apparent Total Tract Nutrient Digestibility
The apparent total tract digestibility of the nutrients starch, EE, CP, NDF,
ADF, hemicellulose, dry matter and organic matter are shown in Tables 13 and
14. Dry matter digestibility had a tendency (P = 0.08) to be greater in step-1,
73.79 vs. 60.13% for the alfalfa strategy compared to the cotton burrs strategy.
There was a tendency (P = 0.06) during the finishing phase for the cotton burrs
strategy to have improved digestibility (76.17% vs. 70.65%) over alfalfa hay
strategy. Organic matter had a tendency to be greater in the alfalfa hay strategy (P
= 0.08) in step 1 (75.80% vs. 61.68%). During the finishing phase for organic
matter digestibility, the roles were switched and the cotton burrs had a greater
digestibility (P < 0.01) at 77.63 vs. 72.02% over the alfalfa hay adaptation
strategy. The NDF digestibility was greater (P = 0.01) for the cotton burrs
strategy than the alfalfa hay strategy during step 4. The ADF digestibility in the
alfalfa hay strategy had a tendency to be greater during (P = 0.06) step-1 (54.81
vs. 22.65%), and greater (P < 0.01) during step-3 (37.68 vs. 15.18%,
respectively). Hemicellulose was also more digestible (P = 0.02) during step 3 for
the alfalfa hay strategy (42.76 vs. 32.27%) compared with cotton burrs strategy.
Crude protein showed greater digestibility (P = 0.03) during step 1 for alfalfa hay
(78.50 vs. 59.47%) compared with cotton burrs strategy. The same pattern tended
(P = 0.07) to be repeated in step 2 (69.94 vs. 64.53%). Starch digestibility was
similar between both treatments except step 1, where alfalfa hay strategy had
greater (P = 0.02) starch digestibility at 98.26 vs. 92.76% compared with cotton
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burrs strategy. For EE, steer fed during step 1 showed greater digestibility in the
alfalfa hay (P < 0.01) at 95.57 vs. 93.31%.
Ruminal In Situ Wheat Hay Degradability
In situ degradability is shown in Tables 15 to 19. No interaction between
treatment and time (P ≥ 0.13), neither main effects of treatment (P ≥ 0.36) was
observed. In all cases and during all steps, as incubation time increased, the
amount of material degraded also increased (P < 0.01).
Feeding Behavior
Feeding behavior is shown in Tables 20 and 21. No differences in total
resting or ruminating behavior were observed (P > 0.05). During step 2, the
alfalfa strategy cattle spent more (P < 0.01) time ruminating while standing up,
and more total time (P = 0.05) resting than the cotton burrs strategy cattle. Cotton
burrs strategy cattle spent more (P = 0.03) time being active during step 2 than the
alfalfa strategy adapted steers. During step 3, the alfalfa strategy steers spent more
time (P = 0.02) ruminating while standing up than cotton burrs strategy steers.
During steps 4, the alfalfa strategy steers spent less time (P = 0.03) ruminating
while laying down than the cotton burrs strategy steers, and had a tendency (P =
0.08) to spend more total time resting during the day than the alfalfa adapted
cattle. During the finishing step, the time spent ruminating per unit of NDF had a
tendency (P = 0.10) to be lower for cotton burrs strategy compared to alfalfa hay
at 243 min/kg daily of NDF as compared to 197 min/kg daily of NDF intake.
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Discussion
Adapting cattle to high concentrate diets efficiently to improve growth
performance while avoiding nutritional health issues is very important. During the
adaptation period cattle were adapted from a wheat hay diet to a 65% steam-
flaked corn-based finishing diet, using cotton burrs or alfalfa hay as a roughage
source. The DMI between the two strategies did not differ during the six periods.
One of the issues with adapting cattle is not only being concerned about the
ruminal microbiota adaptation effects, but also factors that may trigger animal
satiety, regardless of by gut fill or ruminal chemical receptors (Church, 1993). By
increasing the time spent to adapt cattle to finishing diets, gut fill and eventually
chemical receptors can determine intake, reducing the intake variation observed
when cattle are adapted quickly (Choat et al., 2002). Adapting cattle over longer
periods of time may attribute to less inconsistency in intake. The ruminal pH
variables may not have varied as much as other studies because steers were
adapted over a period of 6 weeks rather rapid adaptation has more effect on the
ruminal pH variance compared to slower, more controlled adaptations (Bevans et
al., 2005).
According to Hill et al. (2000), cattle fed diets made primarily of cotton
burrs had decreased intakes compared to cattle grazing grass for the first ten days
as cattle adjusted to the physical aspect of cotton burrs. This may not be the case
in current study, and the lack of difference in intakes showed cattle
physiologically accepted the cotton burrs as an acceptable ingredient in the diet
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and did not negatively react to the cotton burrs, when compared to alfalfa hay.
The cotton burrs adaptation strategy appeared to have a lower average rumen pH
and more consistent day-to-day average pH than the traditional alfalfa hay
strategy. While this may be viewed as a negative aspect because a large part of
adapting cattle to finishing diets is to avoid ruminal acidosis and the resultant
liver abscesses, other aspects of the ruminal environment that were measured
portray this as a potentially positive result of feeding cotton burrs rather than
alfalfa hay during adaptation strategies. While the cotton burrs strategy steers had
a lower average ruminal pH, only during step 3 did the steers spend more time
below a ruminal pH of 5.6 than steers fed the alfalfa hay strategy. Bevans et al.
(2005) observed lower ruminal pH could be due to increased VFA loads as cattle
were adapted to high concentrate diets rather than lactic acid production,
especially if diet increases were done over longer periods of time. Throughout the
finisher diet, which was common between both strategies, the cotton burrs
strategy tended to spend more time below a pH of 5.0 than the alfalfa hay
strategy. This reduction in ruminal pH could be due to an increase in VFA
present in the rumen from improved access to nutrients. Fernando et al. (2010)
observed an increase in anaerobic and amylolytic bacteria within the rumen as the
concentrate in the diet increased during the adaptation phase. As concentrate in
the diet increases, Fernando et al. (2010) observed a decrease in bacterial
populations that could digest both fibre and starch, due to decreased ruminal pH
average. This would help in the shift of microbial population to more amylolytic
bacteria (Fernando et al., 2010). The reduction in ruminal pH even in the finishing
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phase for the cotton burrs strategy steers may have been due to an increased rate
of VFA production which was greater than the absorption, if the animal can make
overcome this drawback, where more energy become available (Anderson et al.,
2015). This is potentially the case because although it was a lower average
ruminal pH, the cotton burrs strategy steers did not spend much more time under
acute or even sub acute acidotic conditions compared to alfalfa hay strategy.
Despite the fact no differences in DMI were observed, the ruminal pH variables
were affected by changes in the diet composition, as well as the apparent total
tract nutrient digestibility. As the rumen was adapted to the high concentrate diets,
digestibility of the diets in either strategy transitioned from better apparent
digestibility in step 1 for the cotton burrs, to better digestibility for alfalfa hay
strategy in step 3. As the diet changes and starch becomes the main ingredient in
the diet, the ruminal microbial population becomes less diverse, which should
ideally make the two strategies become more similar in all aspects as the finishing
diet is approached (Fernando et al., 2010, Anderson et al., 2015). It would be
anticipated that alfalfa hay would have better apparent digestibility compared to
cotton burrs because it is a high quality roughage source. The current study was
designed to observe the effect of cotton burrs and evaluate its effect against a
known adaptation strategy such as alfalfa hay. The reduction in ruminal pH and
the increase in organic matter digestibility in the finishing diet of those steers
adapted using the cotton burrs strategy suggests the cotton burrs strategy had
some underlying effects on steer performance and microbial population as
compared to the alfalfa hay strategy. Although a lower ruminal pH was observed,
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which is a cause of concern of ruminal acidosis during the finishing phase of
steers, this ruminal pH may be what the steer is acclimated to, and further
finishing growth performance analysis would have to be researched before
drawing a more abroad implication. That being said, with the increase in organic
matter digestibility, some of it may be attributed to the ruminal digestibility,
which would decrease ruminal pH with more starch being fermented and acids
being produced within the rumen, causing that reduction in ruminal pH average,
while supplying ruminal microbiota with more substrate for development. Current
data pairs well with the ammonia, as lower ruminal ammonia levels are noted in
steers adapted using the cotton burrs strategy diet during steps 1 and 3, and a
tendency during step 4. A reduction in ammonia concentration within the rumen
suggests that ruminal microbiota utilized more efficiently the N available from
diet, (Moloney and Drennan, 1994). While microbes are utilizing the protein
within the diet, the improved digestibility of organic matter would be explained
because microbes are utilizing both (energy and protein) to induce ruminal
development, and at same time have a stable ruminal environment. Although the
cotton burrs strategy was seen negatively in terms of ruminal pH variables, it
could be an indication that cotton burrs better equips the rumen for the high starch
load diets and may help improve growth performance and efficiency of the rumen
microbial synthesis, and thus the animal under feedlot conditions. Further
research is needed to confirm finishing growth performance after the adaptation
phase.
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Ruminal in situ degradation was not different between the two strategies
for any of the nutrients evaluated during all six periods. As noted above, no
differences between the two strategies were positive because it meant cotton burrs
were just as capable as alfalfa hay in the adaptation phase. In situ degradation
evaluated the fiber degradability of wheat hay during all six periods. Not
surprisingly, all fiber fractions endured increased degradation as the time
increased from 0 to 48 hours. Due to the fact it was a common fiber source
utilized to analyze the rumen degradability, any major differences in the rumen
environments between the two strategies would have been noted in how well fiber
was degraded. If the ruminal environments had changed as a result of the different
ingredients, it was hypothesized the ability of the rumen to degrade the fiber
fractions would have been different, because cellulolytic bacteria play such an
important role in the degradation.
Feeding behavior is another indicator of how cattle respond to new diets.
The physical activity of chewing by the animal to induces feedstuff nutrient
utilization by the microbiota digestion (Beauchemin et al., 1994). Increasing
chewing time has increased ruminal degradation and increased fiber digestion
(Beauchemin et al., 1994). Unfortunately, differences in chewing or ruminating
times were not documented in current study, showing digestibility and ruminal
degradability occurred due to chemical and microbial response of the rumen,
rather than induced by changes in behavioral perception of the adaptation
strategies. Despite the fact some studies have observed cattle do not always
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respond well to cotton burrs added to the diet (Hill et al., 2000), the cattle in
current study did not show any apparent effect on intake and showed adequate
adaptation patterns throughout the feeding periods. The measurement of cattle
chewing, ruminating, and eating activities help to better understand potential
positive effects due to chewing on buffering in the rumen (saliva production), and
differences between behaviour might also explain some of the differences noted
in pH and VFA levels within the rumen. While there were slight differences in
times spent ruminating while lying down or standing up between the two
strategies, there were no differences between total time spent ruminating or
chewing. As suggested above in the discussion about the ruminal pH variables,
the response in the rumen was chemical rather than a physiological response to
the diet. That being said, more time was spent ruminating per unit of NDF intake
during the finishing diet for the cattle adapted through the alfalfa strategy. This
tendency for an increase in rumination activity may have lasting effects
throughout the growth performance phase as cattle combat the effects of low
ruminal pH. Increased chewing time increases saliva production, which increases
ruminal pH because of its buffer like properties (Beauchemin et al., 2005). These
results are a benefit of alfalfa hay over the cotton burrs strategy. However, as
observed in earlier periods, the rumen of cattle adapted in the cotton burrs strategy
had lower average ruminal pH during a couple steps, suggesting while the ruminal
pH was low, it was not in harmful acidotic levels for the rumen. The decreased
chewing time and decreased ruminal pH, while lower, may not negatively impact
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growth performance, as ruminal microbiota that produce propionate may perform
better at lower ruminal pH and have a more stable rumen environment.
Differences in VFA variables between the two adaptation strategies were
observed throughout many of the steps in current study. During step 1, molar
proportions of propionate were greater for the alfalfa strategy over the cotton
burrs strategy. Propionate production results from starch, and growth of
microorganisms, and it is necessary for glucose production for the animal through
gluconeogenic pathways (Bergman et al., 1990). Propionate is largely taken up by
the liver to be converted to glucose, and used as an energy source (Bergman et al.,
1990). The improved propionate molar proportion during step-1 may be due to the
increased starch in the diet. In addition, alfalfa hay is a high quality roughage
source and provides energy that cotton burrs perhaps does not possess. A
tendency for propionate improved during step 2 may have been a result of
microbes in the rumen that were acclimated to getting as much starch out of the
inclusion of the steam-flaked corn, and were more able to produce propionate
with the same materials as the alfalfa hay strategy steers as the levels of roughage
decreased. Isobutyrate molar proportions were greater during step 1 for the alfalfa
hay strategy and lower during step 2 for the alfalfa hay strategy. Differences and
the effect of isobutyrate on the rumen were not consequential, as the volatile fatty
acids other than butyrate, acetate and propionate make up less than 5% of the total
acids in the rumen (Bergman et al., 1990). The acetate to propionate ratio had a
tendency to be higher for the alfalfa hay strategy than the cotton burrs strategy,
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which worked perfectly in line with the increased propionate proportion with the
cotton burrs strategy. Valerate molar proportions were greater during step 4 and
the finisher period for the cotton burrs strategy, however, because they represent
less than 5% of total VFA production, it may not be of concern. The results from
the VFA show that even though cattle were adapted using a lower quality
roughage source such as cotton burrs, ruminal VFA molar proportions were not
harmed and cattle were able to efficiently degrade and utilize the roughage
source, as noted with no differences in total VFA ruminal concentration
throughout any of the six periods.
Implications
Some of the current challenges of adapting cattle to high concentrate diets
using traditional roughage sources can be alleviated using cotton burrs. Cotton
burrs are widely available in the southern United States and appear to be able to
provide an alternative for feedlot producers adapting cattle to high concentrate
diets. Cotton burrs may be a cost effective alternative strategy that does not
negatively affect ruminal metabolic variables. Some care does need to be taken
with feeding the cotton burrs as the ruminal pH of those cattle fed cotton burrs
was lower and might lead to acidotic conditions if not monitored carefully.
However, with proper management and feeding techniques this lower ruminal pH
during the early periods of adaptation may acclimate the rumen more effectively
to high concentrate loads, as finishing diet apparently digestibility increased. The
cotton burrs strategy appears to provide a better ruminal fermentation
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environment than the alfalfa adaptation strategy, albeit with a riskier average
ruminal pH pattern. When considering cost of the roughage, cotton burrs might
provide an alternative if available at a reasonable cost. Further research is
required to further determine the effect of cotton burrs during the adaptation phase
on cattle growth performance, economic value and resultant carcass
characteristics during the finishing phase.
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Table 7. Dietary composition of adaptation diets using cotton burrs or alfalfa hay as a roughage source. Adaptation periods Ingredient, % DM Wheat Hay Step 1 Step 2 Step 3 Step 4 Finisher Alfalfa Hay Strategy Wheat Hay 98.50 - - - - - Mineral 1.50 - - - - - Steam Flaked Corn - 30.68 38.18 45.68 53.18 60.68 Alfalfa Hay - 30.00 22.50 15.00 7.50 - Cotton Burr - - - - - - Corn Silage - 7.50 7.50 7.50 7.50 7.50 Sorghum Silage - 7.50 7.50 7.50 7.50 7.50 WCGF, Sweet Bran - 15.00 15.00 15.00 15.00 15.00 TTU Supplement - 2.00 2.00 2.00 2.00 2.00 Cottonseed Meal - 1.20 1.20 1.20 1.20 1.20 Tallow - 3.50 3.50 3.50 3.50 3.50 Limestone - 1.78 1.78 1.78 1.78 1.78 Urea - 0.84 0.84 0.84 0.84 0.84 Cotton Burrs Strategy Wheat Hay 98.50 - - - - - Mineral 1.50 - - - - - Steam Flaked Corn - 30.68 38.18 45.68 53.18 60.68 Alfalfa Hay - - - - - - Cotton Burr - 30.00 22.50 15.00 7.50 - Corn Silage - 7.50 7.50 7.50 7.50 7.50 Sorghum Silage - 7.50 7.50 7.50 7.50 7.50 WCGF, Sweet Bran - 15.00 15.00 15.00 15.00 15.00 TTU Supplement - 2.00 2.00 2.00 2.00 2.00 Cottonseed Meal - 1.20 1.20 1.20 1.20 1.20 Tallow - 3.50 3.50 3.50 3.50 3.50 Limestone - 1.78 1.78 1.78 1.78 1.78 Urea - 0.84 0.84 0.84 0.84 0.84
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Table 8. Analyzed nutritional composition of adaptation diets using cotton burrs or alfalfa hay as a roughage source. Adaptation periods Nutrient, % DM
Wheat Hay
Step 1 Step 2 Step 3 Step 4 Finisher
Alfalfa Hay Strategy Starch 1.50 28.60 30.70 41.40 44.10 41.60 Ether Extract 1.10 6.10 6.30 5.90 7.20 7.40 NDF 60.75 28.48 25.91 23.06 20.57 17.35 ADF 32.51 15.17 13.60 11.16 8.69 6.43 Hemicellulose 28.24 13.31 12.31 11.90 11.88 10.91 Crude Protein 9.55 16.40 16.33 14.63 16.02 15.67 Ash 8.18 8.35 7.94 5.98 5.70 6.30 Cotton Burrs Strategy Starch 1.50 26.20 29.70 37.70 42.40 41.60 Ether Extract 1.10 5.30 6.20 6.60 7.30 7.40 NDF 60.75 29.09 26.49 22.87 19.92 17.35 ADF 32.51 16.55 14.43 11.06 8.84 6.43 Hemicellulose 28.24 12.54 12.06 11.80 11.07 10.91 Crude Protein 9.55 14.44 14.43 17.34 15.57 15.67 Ash 8.18 10.22 8.65 7.53 6.21 6.30
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Table 9. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on dry matter intake, ruminal parameters-Wheat Hay, Step 1 and 2. Wheat Hay Step 1 Step 2 Adaptation
Strategy SEM1 P-
Value Adaptation
Strategy SEM1 P -
Value Adaptation
Strategy SEM1 P -
Value Variables Alfalfa Cotton Alfalfa Cotton Alfalfa Cotton Roughage Inclusion, % DM
30.00 30.00 22.50 22.50
DMI, kg/d 4.86 4.43 0.440 0.16 5.85 6.33 0.240 0.24 7.04 7.45 0.547 0.36 Ruminal pH Parameters
Average 6.58 6.34 0.082 0.11 5.86 5.94 0.098 0.62 5.78 5.66 0.030 0.01 Variance 0.01 0.04 0.048 0.81 0.10 0.07 0.014 0.16 0.13 0.11 0.026 0.71 Maximum 6.80 6.64 0.080 0.24 6.48 6.57 0.127 0.69 6.46 6.31 0.052 0.11 Minimum 6.30 5.89 0.151 0.13 5.27 5.37 0.097 0.64 4.79 5.07 0.209 0.42 Time Below 5.6, min/d 0.02 21.40 9.132 0.17
318.86 320.86 124.370 0.99
452.47 664.10 91.248 0.39
Area below 5.6, min*pH 0.00 1.53 0.575 0.13
61.60 45.04 20.923 0.63
104.17 162.13 28.652 0.24
Time Below 5.0, min/d 0.00 0.00 0.000 0.00
0.80 0.00 0.526 0.30
11.57 32.99 22.306 0.59
Area below 5.0, min*pH 0.00 0.00 0.000 0.00
0.00 0.00 0.00 0.00
6.33 2.84 4.006 0.62
Ammonia Concentration Ammonia (mg/L) 1.68 1.73 0.923 0.34 18.74 11.27 1.403 0.02 10.45 10.50 1.947 0.99 1Standard error of the mean
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Table 10. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on dry matter intake, ruminal parameters-Steps 3 and 4, Finisher. Step 3 Step 4 Finisher Adaptation
Strategy SEM1 P - Value
Adaptation Strategy SEM1
P - Value
Adaptation Strategy SEM1
P - Value
Variables Alfalfa Cotton Alfalfa Cotton Alfalfa Cotton Roughage Inclusion, % DM
15.00 15.00 7.50 7.50
DMI, kg/d 7.43 7.87 0.233 0.22 7.32 7.71 0.526 0.39 7.85 7.89 0.953 0.38 Ruminal pH Parameters
Average 6.04 5.62 0.049 <0.01 5.80 5.79 0.114 0.98 5.83 5.51 0.083 0.05 Variance 0.105 0.133 0.049 0.72 0.104 0.094 0.026 0.82 0.102 0.118 0.029 0.70 Maximum 6.44 6.52 0.091 0.31 6.45 6.37 0.045 0.33 6.48 6.20 0.062 0.05 Minimum 5.30 4.65 0.308 0.22 5.09 4.84 0.229 0.54 5.18 4.86 0.117 0.12 Time Below 5.6, min/d 159.59 599.33 103.29 0.10
416.01 376.84 162.13 0.88
356.74 804.46 174.73 0.13
Area below 5.6, min*pH 15.16 200.42 24.626 <0.01
133.09 71.78 60.386 0.53
97.35 258.11 66.550 0.16
Time Below 5.0, min/d 0.00 59.73 5.896 0.02
41.06 0.00 29.17 0.35
4.86 119.90 39.635 0.08
Area below 5.0, min*pH 5.50 6.95 10.600 0.93
4.85 0.00 2.795 0.24
2.47 13.31 3.126 0.15
Ammonia Concentration Ammonia (mg/L) 8.82 5.06 1.019 <0.01 6.75 5.00 0.543 0.10 7.01 5.16 0.814 0.21 1Standard Error of the mean
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Table 11. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on ruminal volatile fatty acid profile-Wheat Hay, Step 1 and 2. Wheat Hay Step 1 Step 2 Adaptation
Strategy SEM1 P -Value
Adaptation Strategy SEM1
P - Value
Adaptation Strategy SEM1
P -Value
Variables Alfalfa Cotton Alfalfa Cotton Alfalfa Cotton Roughage Inclusion, % DM
30.00 30.00 22.50 22.50
Total, mmol/L 82.018 84.021 5.5304 0.81 102.280 103.790 6.5647 0.88 139.940 112.480 11.7390 0.12 C2:C3 3.812 3.744 0.0418 0.27 2.583 2.877 0.2215 0.44 1.757 1.350 0.1120 0.09
Molar Proportion, mmol/100 mmol Acetate 69.997 70.586 0.4022 0.33 58.656 58.575 1.6458 0.97 48.169 48.259 2.1594 0.98 Propionate 18.357 18.934 0.1110 <0.01 23.915 20.187 0.6865 0.03 29.411 34.901 1.705 0.08 Butyrate 9.224 8.735 0.2192 0.11 14.253 18.078 1.9245 0.23 14.872 17.998 2.9765 0.36 Isobutyrate 0.765 0.552 0.0619 0.02 0.811 0.490 0.06195 <0.01 0.418 0.541 0.04195 0.09 Valerate 0.646 0.651 0.0469 0.94 1.506 1.665 0.2108 0.62 1.365 1.303 0.1760 0.82 Isovalerate 0.880 0.671 0.1109 0.25 0.995 0.868 0.1371 0.55 1.468 1.298 0.4379 0.78 1Standard Error of the Mean
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Table 12. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on ruminal volatile fatty acid profile-Step 3, 4 and Finisher. Step 3 Step 4 Finisher Adaptation
Strategy SEM1 P -Value
Adaptation Strategy SEM1
P - Value
Adaptation Strategy SEM1
P -Value
Variables Alfalfa Cotton Alfalfa Cotton Alfalfa Cotton Roughage Inclusion, % DM
15.00 15.00 7.50 7.50
Total, mmol/L 133.930 147.760 11.200 0.44 123.920 117.590 4.2833 0.31 136.250 134.560 8.0015 0.88 C2:C3 2.263 0.973 0.639 0.21 1.237 1.098 0.0997 0.38 0.996 0.984 0.0973 0.83
Concentrations, mmol/100 mmol Acetate 49.076 44.539 3.940 0.52 49.027 47.474 1.5243 0.51 43.357 44.062 3.1076 0.88 Propionate 36.203 39.207 5.406 0.71 40.267 43.304 2.0364 0.35 45.169 45.626 3.4058 0.91 Butyrate 13.157 12.101 1.495 0.64 7.571 5.758 1.0173 0.27 5.920 7.712 1.3885 0.42 Isobutyrate 0.368 0.204 0.137 0.45 0.229 0.198 0.0470 0.67 0.148 0.167 0.0812 0.88 Valerate 1.320 1.562 0.232 0.50 1.523 2.395 0.1956 0.04 1.497 2.774 0.2669 0.03 Isovalerate 1.435 0.828 0.188 0.08 1.262 0.990 0.1644 0.28 1.570 2.002 0.5453 0.54
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Table 13. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on apparent total tract nutrient digestibility-Wheat Hay, Step 1 and 2.
Wheat Hay Step 1 Step 2
Adaptation
Strategy SEM1 P -
Value Adaptation
Strategy SEM1 P -
Value Adaptation
Strategy SEM1 P -
Value Variables Alfalfa Cotton Alfalfa Cotton Alfalfa Cotton
Roughage Inclusion, % DM
30.00 30.00 22.50 22.50
Apparent Total Tract Digestibility, % DM basis Dry Matter 66.58 67.96 0.657 0.21 73.79 60.13 4.146 0.08 67.21 67.43 1.293 0.91
Organic Matter 68.85 70.41 0.718 0.20
75.80 61.68 4.280 0.08
68.93 70.09 1.147 0.51
NDF 70.97 72.82 0.524 0.07 51.64 38.50 9.319 0.38 36.31 39.20 4.191 0.65 ADF 71.11 73.03 0.901 0.21 54.81 22.65 11.893 0.06 35.32 32.22 3.807 0.60
Hemicellulose 70.69 72.71 0.194 <0.01 54.29 33.18 7.794 0.13 37.66 46.40 4.754 0.26 Crude Protein 57.95 61.31 1.075 0.09 78.50 59.47 3.817 0.03 69.94 64.53 1.586 0.07 Ether Extract 50.77 49.38 1.256 0.48 95.57 93.31 0.412 0.10 93.84 94.97 0.454 0.15
Starch 97.97 97.94 0.080 0.81 98.26 92.76 1.008 0.02 96.95 97.27 0.836 0.78 1Standard Error of the Mean
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Table 14. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on apparent total tract nutrient digestibility-Step 3 and 4, Finisher.
Step 3 Step 4 Finisher
Adaptation
Strategy SEM1 P -
Value Adaptation
Strategy SEM1 P -
Value Adaptation
Strategy SEM1 P -
Value Variables Alfalfa Cotton Alfalfa Cotton Alfalfa Cotton
Roughage Inclusion, % DM
15.00 15.00 7.50 7.50
Apparent Total Tract Nutrient Digestibility, % DM Basis
Dry Matter 71.56 67.79 3.410 0.48 65.36 67.52 3.054 0.64 70.65 76.17 1.653 0.06 Organic Matter 73.89 69.21 2.626 0.28 67.29 69.20 2.868 0.66 72.02 77.63 1.614 < 0.01 NDF 37.42 28.04 4.238 0.15 17.88 31.18 3.230 0.01 36.12 36.85 3.622 0.90 ADF 37.68 15.18 3.481 < 0.01 16.37 22.83 4.870 0.41 32.60 32.52 3.564 0.99 Hemicellulose 42.76 32.27 3.913 0.02 20.49 29.39 4.719 0.28 38.18 39.39 3.848 0.84 Crude Protein 69.60 66.52 2.201 0.20 61.78 62.73 3.671 0.86 62.59 71.76 3.176 0.19 Ether Extract 94.70 93.52 1.162 0.50 93.43 93.84 0.656 0.68 94.15 95.19 0.603 0.15 Starch 96.80 95.59 1.001 0.44 95.92 95.89 0.561 0.97 96.50 96.33 0.329 0.73 1Standard Error of the Mean
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Table 15. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on in situ ruminal dry matter degradability. In Situ DM Degradability, %
Time in Rumen (h)
SEM1
P -Value
Trt
P – Value Time
P – Value
Trt*time Variables Alfalfa Cotton 0 12 24 48 0 12 24 48 Wheat Hay 41.71 50.64 60.34 67.99 42.11 50.78 57.91 66.42 2.529 0.78 <0.01 0.82 Step 1 41.71 47.05 54.41 60.31 42.11 48.58 53.52 61.42 4.783 0.93 <0.01 0.98 Step 2 41.71 47.26 53.65 62.30 42.11 48.40 53.98 63.84 4.421 0.86 <0.01 1.00 Step 3 41.71 47.24 53.79 58.66 42.11 49.13 59.55 74.68 4.997 0.36 <0.01 0.13 Step 4 41.71 47.06 55.11 62.16 42.11 51.46 56.76 64.71 5.250 0.73 <0.01 0.95 Finisher 41.71 48.77 55.40 62.00 42.11 52.03 56.51 65.92 4.454 0.70 <0.01 0.92 1Standard Error of the Mean
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Table 16. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on in situ ruminal organic matter degradability. In Situ OM Degradability, %
Time in Rumen (h)
SEM1
P – Value trt
P – Value time
P – Value Trt*time
Variables Alfalfa Cotton 0 12 24 48 0 12 24 48 Wheat Hay 39.69 48.80 59.16 67.16 40.06 49.04 56.40 65.46 2.699 0.77 <0.01 0.81 Step 1 39.69 45.11 53.00 59.19 40.06 46.70 51.95 60.21 5.086 0.94 <0.01 0.98 Step 2 39.69 45.27 52.05 61.31 40.06 46.57 52.47 62.77 4.682 0.88 <0.01 0.99 Step 3 39.69 45.40 52.26 57.53 40.06 47.34 58.29 74.20 5.281 0.36 <0.01 0.15 Step 4 39.69 45.11 53.74 61.14 40.06 49.67 55.28 63.68 5.582 0.74 <0.01 0.95 Finisher 39.69 46.93 53.90 60.96 40.06 50.27 55.08 64.93 4.703 0.70 <0.01 0.93 1Standard Error of the Mean
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Table 17. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on in situ ruminal neutral detergent fiber degradability. In Situ NDF Degradability, %
Time in Rumen (h)
SEM1
P – Value
trt
P – Value time
P – Value
Trt*time Variables Alfalfa Cotton 0 12 24 48 0 12 24 48 Wheat Hay 20.17 35.54 44.93 56.17 19.97 35.93 40.20 53.27 5.017 0.75 <0.01 0.88 Step 1 20.17 31.50 37.10 45.60 19.97 32.44 33.88 45.50 8.032 0.95 <0.01 0.98 Step 2 20.17 32.17 39.59 48.92 19.97 33.22 35.33 49.92 7.861 0.95 <0.01 0.95 Step 3 20.17 31.49 39.87 44.03 19.97 33.96 42.65 65.32 8.481 0.54 <0.01 0.25 Step 4 20.17 26.14 41.44 48.66 19.97 36.10 43.88 51.24 9.120 0.73 <0.01 0.88 Finisher 20.17 28.11 41.99 48.29 19.97 36.62 43.06 52.83 7.701 0.71 <0.01 0.84 1Standard Error of the Mean
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Table 18. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on in situ ruminal acid detergent fiber degradability. In Situ ADF Degradability, %
Time in Rumen (h)
SEM1
P – Value
trt
P – Value time
P – Value
Trt*time Variables Alfalfa Cotton
0 12 24 48 0 12 24 48 Wheat Hay 11.25 32.83 40.17 51.47 12.27 31.17 34.25 49.15 8.252 0.81 <0.01 0.96 Step 1 11.25 24.60 30.88 40.11 12.27 27.02 24.44 40.51 11.894 0.96 <0.01 0.94 Step 2 11.25 30.42 37.25 43.93 12.27 29.90 25.92 45.94 11.552 0.88 <0.01 0.80 Step 3 11.25 27.99 37.80 38.41 12.27 32.77 32.28 62.93 11.879 0.67 <0.01 0.31 Step 4 11.25 16.68 38.96 44.14 12.27 33.27 37.97 46.95 12.563 0.75 <0.01 0.75 Finisher 11.25 19.96 39.92 43.70 12.27 34.36 34.23 49.03 11.587 0.78 <0.01 0.68 1Standard Error of the Mean
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Table 19. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on in situ ruminal hemicellulose degradability. Hemicellulose Degradability, %
Time in Rumen (h)
SEM1
P – Value
trt
P – Value time
P – Value
Trt*time Variables Alfalfa Cotton
0 12 24 48 0 12 24 48 Wheat Hay 30.44 38.65 50.41 61.57 28.83 42.33 47.04 58.00 3.325 0.66 <0.01 0.66 Step 1 30.44 47.56 44.26 51.93 28.83 41.24 49.13 51.26 7.377 0.87 0.03 0.90 Step 2 30.44 34.19 42.28 54.66 28.83 37.03 48.47 54.49 4.769 0.69 <0.01 0.81 Step 3 30.44 35.53 42.26 50.50 28.83 35.32 43.08 68.07 5.563 0.50 <0.01 0.17 Step 4 30.44 37.03 44.29 53.85 28.83 39.36 53.21 56.18 6.231 0.64 <0.01 0.80 Finisher 30.44 37.49 44.37 53.58 28.83 39.22 47.83 57.21 4.970 0.75 <0.01 0.90 1Standard Error of the Mean
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Table 20. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on feeding behavior-Wheat Hay, Step 1 and 2. Wheat Hay Step 1 Step 2 Adaptation
Strategy SEM1 P -Value
Adaptation Strategy SEM1
P - Value
Adaptation Strategy SEM1
P - Value
Variables Alfalfa Cotton Alfalfa Cotton Alfalfa Cotton Roughage Inclusion, % DM
30.00 30.00 22.50 22.50
Feeding behavior, min/d Eating 318 297 24.6 0.57 218 267 50.4 0.54 235 258 25.6 0.56 Drinking 2 5 2.4 0.37 10 25 6.8 0.19 20 13 4.3 0.33 Ruminating Up 152 167 23.4 0.67 55 31 13.7 0.30 43 5 3.7 < 0.01 Ruminating Down 387 373 41.4 0.83 445 375 28.9 0.16 452 490 25.3 0.34 Resting Up 147 177 39.1 0.62 153 123 22.1 0.39 132 113 26.4 0.65 Resting Down 390 347 29.8 0.36 492 491 64.6 1.00 480 417 22.4 0.12 Active 45 75 15.7 0.25 67 127 13.9 0.04 78 143 13.2 0.03 Total Resting 537 523 22.6 0.70 645 615 63.4 0.75 612 530 21.1 0.05 Total Ruminating 538 540 24.9 0.96 500 407 41.6 0.21 495 495 31.5 1.00 Chewing 857 837 17.4 0.46 750 641 51.6 0.25 731 753 28.2 0.63 Rumination/kg NDF consumed 346 378 49.5 0.67
236 210 29.2 0.58
290 257 29.5 0.50
Chewing/kg NDF Consumed 544 588 68.1 0.68
342 349 50.5 0.93
425 397 52.3 0.74
1Standard Error of the Mean
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Table 21. Effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on feeding behavior-Step 3 and 4, Finisher. Step 3 Step 4 Finish Adaptation
Strategy SEM1 P -Value
Adaptation Strategy SEM1
P - Value
Adaptation Strategy SEM1
P -Value
Variables Alfalfa Cotton Alfalfa Cotton Alfalfa Cotton Roughage Inclusion, % DM
15.00 15.00 7.50 7.50
Feeding Behavior, min/day Eating 243 232 17.3 0.66 170 195 17.4 0.37 167 168 31.9 0.97 Drinking 20 18 5.5 0.84 13 33 4.9 0.04 23 45 11.4 0.25 Ruminating Up 20 5 2.9 0.02 28 3 9.3 0.13 25 10 8.4 0.27 Ruminating Down 447 485 26.5 0.36
415 457 8.7 0.03
378 337 29.3 0.37
Resting Up 117 97 34.9 0.71 145 120 26.8 0.55 190 167 43.4 0.72 Resting Down 462 487 28.0 0.56 532 485 36.8 0.42 507 552 56.8 0.60 Active 132 117 24.9 0.69 137 147 18.3 0.71 150 162 26.5 0.77 Total Resting 578 583 43.8 0.94 677 605 21.6 0.08 697 718 30.6 0.64 Total Ruminating 466 491 22.5 0.50 443 460 7.0 0.19 404 346 32.5 0.30 Chewing 721 711 43.1 0.88 616 653 24.9 0.39 570 515 30.8 0.31 Rumination/kg NDF consumed 307 276 27.7 0.49
226 248 21.2 0.52
243 197 13.6 0.10
Chewing/kg NDF Consumed 461 410 48.4 0.52
312 354 34.4 0.45
329 301 17.8 0.34
1Standard Error of the Mean
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Figure 3. The effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on average ruminal pH.
5
5.2
5.4
5.6
5.8
6
6.2
6.4
6.6
6.8
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
Wheat Hay Step 1 Step 2 Step 3 Step 4 Finisher
Ave
rage
Rum
inal
pH
Adaptation Steps (days)
Alfalfa Cotton
P = 0.11 P = 0.62 P < 0.01 P < 0.01 P = 0.98 P = 0.05
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Figure 4. The effect of cotton burrs or alfalfa hay as a roughage source during the adaptation period to steam-flaked corn-based finishing diets on average ammonia concentration (mg/L).
0
5
10
15
20
25
30
35
0 4 8 16 0 4 8 16 0 4 8 16 0 4 8 16 0 4 8 16 0 4 8 16
Wheat Hay Step 1 Step 2 Step 3 Step 4 Finisher
Am
mon
ia C
once
ntra
tions
(mg/
L)
Adaptation Steps (hours post feeding)
Alfalfa Cotton
P=0.34P=0.02P=0.99 P<0.01 P=0.10P=0.21