Two experiments were conducted with pregnant yearling heifers grazing Sandhills winter range to evaluate response of supplementing to meet the metabolizable protein requirement of the heifers versus conventional supplementation based on crude protein. Supplements were fed from October to February (pre-calving) both years. Intake was measured in November, January and February of the first year. Supplementing to meet metabolizable protein requirement improved the heifers’ ability to maintain weight in year one, but not in year two. Heifer intakes ranged from 2.2% of BW in November to 1.5% in February. Feeding hay reduced body weight loss compared to no hay feeding in year two

Adams, Don C.

Applegarth, Andy

Klopfenstein, Terry J.

Musgrave, Jacqueline A.

Patterson, Trey

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Nebraska Beef Cattle Reports Animal Science Department 1-1-2000 Supplementing Metabolizable Protein to Yearling Heifers Grazing Winter Range Trey Patterson University of Nebraska-Lincoln Don C. Adams University of Nebraska-Lincoln, dadams1@unl.edu Terry J. Klopfenstein University of Nebraska-Lincoln, tklopfenstein1@unl.edu Jacqueline A. Musgrave University of Nebraska-Lincoln, jmusgrave1@unl.edu Andy Applegarth Gudmundsen Sandhills Laboratory, Whitman, andy.applegarth@unl.edu Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr  Part of the Animal Sciences Commons Patterson, Trey; Adams, Don C.; Klopfenstein, Terry J.; Musgrave, Jacqueline A.; and Applegarth, Andy, "Supplementing Metabolizable Protein to Yearling Heifers Grazing Winter Range" (2000). Nebraska Beef Cattle Reports. 384. https://digitalcommons.unl.edu/animalscinbcr/384 This Article is brought to you for free and open access by the Animal Science Department at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Nebraska Beef Cattle Reports by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Page 7 — 2000 Nebraska Beef Report(Continued on next page)Supplementing Metabolizable Protein to YearlingHeifers Grazing Winter RangeTrey PattersonDon AdamsTerry KlopfensteinJacki MusgraveAndy Applegarth1Supplementing metabolizableprotein to grazing heifers in the win-ter improved performance in one oftwo years, and forage intakesdeclined with increasing stage ofgestation.SummaryTwo experiments were conductedwith pregnant yearling heifers grazingSandhills winter range to evaluate re-sponse of supplementing to meet themetabolizable protein requirement ofthe heifers versus conventional supple-mentation based on crude protein.Supplements were fed from October toFebruary (pre-calving) both years. In-take was measured in November, Janu-ary and February of the first year.Supplementing to meet metabolizableprotein requirement improved the heif-ers’ ability to maintain weight in yearone, but not in year two. Heifer intakesranged from 2.2% of BW in Novemberto 1.5% in February. Feeding hay re-duced body weight loss compared to nohay feeding in year two.IntroductionNutritional systems that facilitate eco-nomical management of yearling heifersover winter to subsequently improve two-year-old pregnancy rate potentially couldimprove ranch profitability. Due to highprotein requirements for growth andpregnancy, metabolizable protein (MP)may become limiting to heifers duringthe winter. Metabolizable protein is thesum of digestible rumen escape protein(UIP) and microbial crude protein (MCP)flowing to the small intestine. The pro-duction of MCP is dependent upon theenergy content of the diet and is thusdecreased as forage quality declines inthe winter. Forage samples collected inthe Sandhills of Nebraska during thewinter with esophageally fistulated cowshave less than 1% of DM as UIP, thusMP will become deficient in situationswhere the requirements are relativelyhigh. Conventional protein supplemen-tation strategies are based on the CPsystem, which erroneously assumes equalrumen degradability of all protein. Insituations where supplemented proteinsources are primarily degraded in therumen, supplements may not supply ad-equate UIP to meet the animals’ MPrequirement. Supplementing to meet MPrequirements during the winter usingsources of protein high in UIP poten-tially could improve performance(weight and body condition) and repro-duction of heifers.A critical step in determining supple-mental requirements of grazing heifersis an accurate estimate of forage intake(FI). Data have not been published on FIof pregnant heifers grazing Sandhillswinter range, nor how FI changes as theheifers progress in gestation. Therefore,the objectives of this study were to evalu-ate the body weight, body condition score(BCS), and FI of pregnant heifers eithersupplemented to meet their MP require-ment or supplemented with a conven-tional protein supplement, and todetermine how FI of heifers changesover the winter.ProcedureExperiment 1Twelve pregnant, yearling heifers(average calving date March 1) grazingnative range at Gudmundsen SandhillsLaboratory were stratified by weight andbody condition score on Oct. 2, 1997and randomly allotted to one of twosupplemental treatments (six per treat-ment). Treatments were 1) a supplementdesigned to meet the MP requirement ofthe heifers through the winter (MPS) and2) a conventional protein supplementfed to meet the CP requirement of theheifers (CONT). Feather meal was usedfor the UIP source in the MPS supple-ment (Table 1), with the supplement DMbeing composed of 49% CP and 27%UIP. The CONT supplement was com-posed of 49% CP and 13% UIP (DMbasis). Supplements were individuallyfed three times weekly starting in mid-October. The CONT supplement wasfed at the rate of .89 lbs/day (DM)throughout the trial, supplying 53 gramsof UIP/day. The MPS supplement feed-ing rate increased gradually from .70 lb/day in October to 1.1 lb/day in Februaryto meet MP requirements, supplying 86grams UIP/day in October, 120 gramsUIP/day in November, December, andJanuary, and 135 grams UIP/day in Feb-ruary. No hay was offered during theTable 1. Composition of supplements fed toheifers in Experiments 1 and 2 (% ofDM).aIngredient MPS CONTCottonseed Meal — 58.8Feather Meal 40.2 —Soybean Meal — 17.8Sunflower Meal 30.2 13.7Wheat Middlings 26.2 —Dist. Grains —   3.4Molasses (Cane)   2.1   2.1Urea —   2.8Minerals/Vitamins   1.3   1.4aSupplements were provided as range cubes fed 3times weekly. MPS: designed to meet themetabolizable protein requirement; CONT:designed as conventional protein supplement.2000 Nebraska Beef Report — Page 8experiment. Beginning Oct. 22, weightswere taken twice weekly and BCS oncemonthly. Weights were taken with noprior shrink at the same time each weigh-day (approximately 1:00 pm), and BCSwere assigned by two trained techni-cians. The heifers were weighed andBCS off-test on Feb. 13, 1998.Heifers were managed in one 81 acrepasture throughout the experiment at astocking rate of .70 AUM/acre. Thepasture was located on a sands rangesite in good to excellent condition whichwas dominated by little bluestem(Schizachyrium scoparium), prairiesandreed (Calamovilfa longifolia), sandbluestem (Andropogon hallii) andswitchgrass (Panicum virgatum). Esti-mates of standing herbage taken from asimilar, adjacent pasture in October(during a simultaneous study; 1999Nebraska Beef Report, pp. 5-6) wereused to calculate cumulative grazingpressure (total AUM per ton of DMforage initially available), which wasabout .59 AUM/ton.Intake measurements were taken inthree, six-day periods beginning Nov.10, 1997, Jan. 5, 1998 and Feb. 9, 1998.Chromium sesquioxide from time releaseboluses was used for determination offecal output in each animal, and predic-tions were validated with four steersusing total fecal collection. Diets werecollected with esophageally fistulatedcows during each intake period, andsamples were used to determine IVDMD.Forage intake was calculated as: dailyfecal output from forage/1-forageIVDMD. Instantaneous grazing pressure(animal units (AU) per ton of DM forageat any instant in time) was about .13, .14and .15 AU/ton for the November, Janu-ary and February intakes, respectively.Experiment 2On Oct. 21, 1998, 18 pregnant heifersat Gudmundsen Sandhills Laboratorywere stratified by weight and BCS andrandomly allotted to one of three supple-mental treatments. Supplements werethe same as those described in Experi-ment 1, and treatments were 1) heiferssupplemented to meet MP requirementand receiving hay beginning in January(MPS/Hay), 2) heifers supplementedwith conventional supplement andreceiving hay beginning in January(CONT/Hay), and 3) heifers supple-mented to meet MP requirement andoffered no hay during the experiment(MPS/No Hay). Heifers were managedon the same pasture described forExperiment 1, with a stocking rate of1.06 AUM/acre and an approximatecumulative grazing pressure of .83AUM/ton (adjusted for hay that wasfed). Hay was individually fed three timesweekly at the rate of 4 lbs/day beginningJan. 4, 1999. The amount was graduallyworked up to 6.5 lbs/day by the first ofFebruary. The hay was late June har-vested meadow hay containing 7.5% CPand was 65.6% digestible (determinedby five day in-vivo trial with five year-ling steers). Supplements were fed asdescribed in the first experiment. Thecattle were weighed twice weekly andBCS every other month. Heifers wereweighed and BCS off-test on Feb. 20 and21, 1999.ResultsExperiment 1Heifers receiving the CONT supple-ment lost 26 lb over the winter, butheifers receiving the MPS treatmentgained 10 lb (Table 2; P = .04). Con-sidering fetal weight (fetus, placenta,fluids) was substantial during the timethe experiment was conducted, all heif-Table 2. Weight, BCS, and forage intake (FI)of heifers grazing winter Sandhillsrange from October 1997 to February1998 (Experiment 1).aItem MPS CONT SDbBeginning wt, lb 955 948 54Final wt, lbc 965 921 49Wt change, lbd 10 -26 27Beginning BCS 6.4 6.3 .5Final BCS 4.9 4.8 .3BCS change 1.5 1.5 .7November FI,e,flb 22.1 20.6 2.5% BW 2.2 2.2 .2January FI,e,flb 17.5 15.8 4.3% BW 1.8 1.7 .4February FI,e,flb 14.8 14.3 2.6% BW 1.5 1.6 .3aMPS: heifers supplemented to meet metabolizableprotein requirement; CONT: heifers supplementedwith conventional protein supplement. No hay fedduring the experiment.bStandard deviation, n = 12.cTreatments differ, P = .16.dTreatments differ, P = .04.eDry matter basis.fIntake declined linearly over time (P = .0001).ers lost body weight over the course ofthe experiment. Figure 1 shows bodyweights of each treatment group through-out the experiment. Both treatmentgroups gained weight from early Octo-ber to late December, and during thisperiod the MPS heifers appeared to gainweight faster than the CONT heifers. Allheifers lost weight in January and Febru-Figure 1. Weight change of heifers in 1997-1998 (Exp. 1).1060104010201000980960940920900Wt, lbMPS: R2=.83CONT: R2=.6610/2 10/17 11/1 11/16 12/1 12/16 12/31 1/15 1/30 2/14Date, 1997-1998Page 9 — 2000 Nebraska Beef Reportthe MPS/Hay treatment had higher BCSin February than those on the MPS/NoHay treatment (5.7 versus 5.0; P = .01),and tended to lose less BCS over thecourse of the experiment (P = .10). Heif-ers on the CONT/Hay treatment tendedto have higher BCS than the MPS/NoHay treatment in February (5.4 versus5.0; P = .10) and tended to lose less BCSover the course of the experiment (P =.16). With weight losses averaging 114lbs for the MPS/No hay treatment com-pared to 26 and 23 lb for the MPS/Hayand CONT/Hay respectively, BCS dif-ferences would be expected to be greaterbetween the hay and no hay treatments.It is possible, however, that less rumenfill in cattle on the MPS/No Hay treat-ment could cause final weights to belower in this treatment relative to treat-ments receiving hay.The addition of MP to the hay-supple-mented diets did not improve the heif-ers’ ability to maintain weight or BCSover conventional supplementation. Theaddition of energy to low-quality rumi-nant diets will increase MCP productionif adequate degradable protein is avail-able. This increases the flow of MP tothe small intestine, and thus will decreasethe need for supplemental UIP. How-ever, this may not fully explain the lackof response to MP in Experiment 2 thatwas noticed in Experiment 1. Yearlyvariation in diet quality can be a factor.Previous work in the Sandhills hasshown that diet quality can change rathermarkedly between years (1998 NebraskaBeef Report, pp. 20-21 ). This can causevariation in intake and performance ofcattle. Figure 2 illustrates that all cattlewere losing weight until hay was fed tothe MPS/Hay and CONT/Hay groups.Heifers were able to maintain bodyweight when hay was fed while heiferson the MPS/No Hay treatment contin-ued to lose weight. This is unlike theresponse noted in Experiment 1 wherecattle gained weight in the fall. Whenenergy is not limiting, one would expecta growth response in the fall from sup-plying UIP, before gestation require-ments and environmental factors beginto play a larger role in the winter months.In Experiment 2, energy could have beenlimiting performance in the fall. ReducedTable 3. Weight and BCS of heifers grazing winter Sandhills range from October 1998 toFebruary 1999 (Experiment 2).aItem MPS/Hay CONT/Hay MPS/No Hay SDbBeginning Wt, lb 940 945 923 41Final Wt, lbc 914 921 808 69Wt change, lbd -26 -23 -114 48Beginning BCS 6.1 6.0 6.1 .4Final BCSe 5.7 5.4 5.0 .5BCS changef -.4 -.6 -1.0 .6aMPS/Hay: heifers supplemented to meet metabolizable protein requirements and fed hay (average 5 lb/day) in January and February; CONT/Hay: heifers supplemented with conventional protein supplementand fed hay in January and February; MPS/No Hay: heifers supplemented to meet metabolizable proteinrequirements and fed no hay.bStandard deviation, n = 18.cMPS/Hay and CONT/Hay versus MPS/No Hay, P = .001.dMPS/Hay and CONT/Hay versus MPS/No Hay, P = .0001.eMPS/Hay versus MPS/No Hay, P = .01; CONT/Hay versus MPS/No Hay, P = .10.fMPS/Hay versus MPS/No Hay, P = .10.ary. It appears that MP was limitinggrowth of the heifers during the fall,while energy became first limiting in lateDecember. There were no differences inBCS loss over the winter between theMPS and CONT heifers (P=.83), withboth groups losing about 1.5 BCS. Mostof this condition loss (approximately66%) occurred after late December, whenweights were declining.Diets collected by the esophageallyfistulated cows during each intake pe-riod had IVDMD averaging 52% inNovember, 49% in January, and 50% inFebruary. Heifer FI was not differentbetween treatments when expressed aslb/day or as a percentage of body weightfor any of the three intake periods (Table2). However, FI declined linearly acrossmeasurement dates (P = .0001). HeiferFI averaged 21.4 lb/day (2.2 % of BW)in November, 16.7 lb/day (1.8%) in Janu-ary, and 14.5 lb/day (1.5%) in February.The 1996 NRC model predicted theheifers to have a DMI of 22 lb/day,which was similar to the FI measured inthese heifers in November. However,the NRC model did not predict a reduc-tion in intake across the measurementdates.A reduction in the amount of forageavailable for grazing and/or stressfulenvironmental conditions can causereductions in intake. In addition, heiferintakes tend to decline as stage of gesta-tion progresses and the fetus and fluidsbegin to compress the rumen, whichreduces rumen volume. Because rumenfill likely limits intake on low qualitydiets, reduced rumen volume results inlower intake. However, the decline in FIover time measured in this study wasmore severe than expected, and the 1.5%of BW intakes measured in Februarywere much lower than intakes measuredin cows grazing similar Sandhills winterrange during late gestation. With actualintakes used as inputs, the NRC modelpredicted the heifers to lose .2 BCS inNovember, .7 BCS in December, and1.4 BCS in January. The heifers actuallylost .3 BCS in November, .5 BCS inDecember, and .6 BCS in January. There-fore, the actual performance was betterthan predicted performance. However,the November intake data yielded pre-dicted BCS losses similar to actual whenmodeled in the NRC. Sources of varia-tion within actual and predicted BCSestimates and the lack of performancemeasurements in late February and earlyMarch (the trial ended) could accountfor the difference in NRC predicted per-formance and actual heifer performancein January (and early February). Thedata show that heifer intakes declined asstage of gestation increased. The declinein intake prior to calving was more se-vere than expected and predicted by theNRC.Experiment 2There were no differences betweenthe MPS/Hay and the CONT/Hay inbody weight change nor BCS change(Table 3). Heifers on the MPS/No Haytreatment lost more weight over thecourse of the winter than heifers on theother treatments (P = .0001 ). Heifers on (Continued on next page)2000 Nebraska Beef Report — Page 10Figure 2. Weight change of heifers in 1998-1999 (Exp. 2).975950925900875850825800Wt, lbCON/Hay: R2=.45MPS/No Hay: R2=.8310/21 11/5 11/20 12/5 12/20 1/4 1/19 2/3 2/18Date, 1998-1999MPS/Hay: R2=.54energy intake was likely due to foragequality and/or the amount of forage avail-able for grazing, as the grazing pressurewas higher in year two. This is furthersupported by the fact that cattle on theMPS/No Hay treatment, which was anidentical treatment to the MPS treatmentin Experiment 1, lost substantially moreweight in Experiment 2. Nevertheless,body condition losses were less inExperiment 2 than in Experiment 1.Rumen-fill differences, error associatedwith comparing BCS data on smallgroups of animals across years and com-position of weight-loss differences couldaccount for some of the year to yearvariation.In conclusion, heifers supplementedwith UIP (balanced MP requirement)maintained more weight in the fall of oneyear, but heifers did not respond to UIPsupplementation in the fall of a secondyear. Year to year variation in foragequality or availability, environment, orother factors could have caused the yeardifferences. Heifer intakes declined asstage of gestation increased. Managingheifers on native range without feedinghay resulted in large losses in bodyweight.1Trey Patterson, research technician, AnimalScience, Lincoln; Don Adams, professor, WestCentral Research and Extension Center, NorthPlatte; Terry Klopfenstein, professor, AnimalScience, Lincoln; Jacki Musgrave, researchtechnician, Andy Applegarth, manager,Gudmundsen Sandhills Laboratory, Whitman.

Supplementing Metabolizable Protein to Yearling Heifers Grazing Winter Range

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
Nebraska Beef Cattle Reports Animal Science Department 
1-1-2000 
Supplementing Metabolizable Protein to Yearling Heifers Grazing 
Winter Range 
Trey Patterson 
University of Nebraska-Lincoln 
Don C. Adams 
University of Nebraska-Lincoln, dadams1@unl.edu 
Terry J. Klopfenstein 
University of Nebraska-Lincoln, tklopfenstein1@unl.edu 
Jacqueline A. Musgrave 
University of Nebraska-Lincoln, jmusgrave1@unl.edu 
Andy Applegarth 
Gudmundsen Sandhills Laboratory, Whitman, andy.applegarth@unl.edu 
Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr 
 Part of the Animal Sciences Commons 
Patterson, Trey; Adams, Don C.; Klopfenstein, Terry J.; Musgrave, Jacqueline A.; and Applegarth, Andy, 
"Supplementing Metabolizable Protein to Yearling Heifers Grazing Winter Range" (2000). Nebraska Beef 
Cattle Reports. 384. 
https://digitalcommons.unl.edu/animalscinbcr/384 
This Article is brought to you for free and open access by the Animal Science Department at 
DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Nebraska Beef Cattle 
Reports by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 
Page 7 — 2000 Nebraska Beef Report
(Continued on next page)
Supplementing Metabolizable Protein to Yearling
Heifers Grazing Winter Range
Trey Patterson
Don Adams
Terry Klopfenstein
Jacki Musgrave
Andy Applegarth1
Supplementing metabolizable
protein to grazing heifers in the win-
ter improved performance in one of
two years, and forage intakes
declined with increasing stage of
gestation.
Summary
Two experiments were conducted
with pregnant yearling heifers grazing
Sandhills winter range to evaluate re-
sponse of supplementing to meet the
metabolizable protein requirement of
the heifers versus conventional supple-
mentation based on crude protein.
Supplements were fed from October to
February (pre-calving) both years. In-
take was measured in November, Janu-
ary and February of the first year.
Supplementing to meet metabolizable
protein requirement improved the heif-
ers’ ability to maintain weight in year
one, but not in year two. Heifer intakes
ranged from 2.2% of BW in November
to 1.5% in February. Feeding hay re-
duced body weight loss compared to no
hay feeding in year two.
Introduction
Nutritional systems that facilitate eco-
nomical management of yearling heifers
over winter to subsequently improve two-
year-old pregnancy rate potentially could
improve ranch profitability. Due to high
protein requirements for growth and
pregnancy, metabolizable protein (MP)
may become limiting to heifers during
the winter. Metabolizable protein is the
sum of digestible rumen escape protein
(UIP) and microbial crude protein (MCP)
flowing to the small intestine. The pro-
duction of MCP is dependent upon the
energy content of the diet and is thus
decreased as forage quality declines in
the winter. Forage samples collected in
the Sandhills of Nebraska during the
winter with esophageally fistulated cows
have less than 1% of DM as UIP, thus
MP will become deficient in situations
where the requirements are relatively
high. Conventional protein supplemen-
tation strategies are based on the CP
system, which erroneously assumes equal
rumen degradability of all protein. In
situations where supplemented protein
sources are primarily degraded in the
rumen, supplements may not supply ad-
equate UIP to meet the animals’ MP
requirement. Supplementing to meet MP
requirements during the winter using
sources of protein high in UIP poten-
tially could improve performance
(weight and body condition) and repro-
duction of heifers.
A critical step in determining supple-
mental requirements of grazing heifers
is an accurate estimate of forage intake
(FI). Data have not been published on FI
of pregnant heifers grazing Sandhills
winter range, nor how FI changes as the
heifers progress in gestation. Therefore,
the objectives of this study were to evalu-
ate the body weight, body condition score
(BCS), and FI of pregnant heifers either
supplemented to meet their MP require-
ment or supplemented with a conven-
tional protein supplement, and to
determine how FI of heifers changes
over the winter.
Procedure
Experiment 1
Twelve pregnant, yearling heifers
(average calving date March 1) grazing
native range at Gudmundsen Sandhills
Laboratory were stratified by weight and
body condition score on Oct. 2, 1997
and randomly allotted to one of two
supplemental treatments (six per treat-
ment). Treatments were 1) a supplement
designed to meet the MP requirement of
the heifers through the winter (MPS) and
2) a conventional protein supplement
fed to meet the CP requirement of the
heifers (CONT). Feather meal was used
for the UIP source in the MPS supple-
ment (Table 1), with the supplement DM
being composed of 49% CP and 27%
UIP. The CONT supplement was com-
posed of 49% CP and 13% UIP (DM
basis). Supplements were individually
fed three times weekly starting in mid-
October. The CONT supplement was
fed at the rate of .89 lbs/day (DM)
throughout the trial, supplying 53 grams
of UIP/day. The MPS supplement feed-
ing rate increased gradually from .70 lb/
day in October to 1.1 lb/day in February
to meet MP requirements, supplying 86
grams UIP/day in October, 120 grams
UIP/day in November, December, and
January, and 135 grams UIP/day in Feb-
ruary. No hay was offered during the
Table 1. Composition of supplements fed to
heifers in Experiments 1 and 2 (% of
DM).a
Ingredient MPS CONT
Cottonseed Meal — 58.8
Feather Meal 40.2 —
Soybean Meal — 17.8
Sunflower Meal 30.2 13.7
Wheat Middlings 26.2 —
Dist. Grains —   3.4
Molasses (Cane)   2.1   2.1
Urea —   2.8
Minerals/Vitamins   1.3   1.4
aSupplements were provided as range cubes fed 3
times weekly. MPS: designed to meet the
metabolizable protein requirement; CONT:
designed as conventional protein supplement.
2000 Nebraska Beef Report — Page 8
experiment. Beginning Oct. 22, weights
were taken twice weekly and BCS once
monthly. Weights were taken with no
prior shrink at the same time each weigh-
day (approximately 1:00 pm), and BCS
were assigned by two trained techni-
cians. The heifers were weighed and
BCS off-test on Feb. 13, 1998.
Heifers were managed in one 81 acre
pasture throughout the experiment at a
stocking rate of .70 AUM/acre. The
pasture was located on a sands range
site in good to excellent condition which
was dominated by little bluestem
(Schizachyrium scoparium), prairie
sandreed (Calamovilfa longifolia), sand
bluestem (Andropogon hallii) and
switchgrass (Panicum virgatum). Esti-
mates of standing herbage taken from a
similar, adjacent pasture in October
(during a simultaneous study; 1999
Nebraska Beef Report, pp. 5-6) were
used to calculate cumulative grazing
pressure (total AUM per ton of DM
forage initially available), which was
about .59 AUM/ton.
Intake measurements were taken in
three, six-day periods beginning Nov.
10, 1997, Jan. 5, 1998 and Feb. 9, 1998.
Chromium sesquioxide from time release
boluses was used for determination of
fecal output in each animal, and predic-
tions were validated with four steers
using total fecal collection. Diets were
collected with esophageally fistulated
cows during each intake period, and
samples were used to determine IVDMD.
Forage intake was calculated as: daily
fecal output from forage/1-forage
IVDMD. Instantaneous grazing pressure
(animal units (AU) per ton of DM forage
at any instant in time) was about .13, .14
and .15 AU/ton for the November, Janu-
ary and February intakes, respectively.
Experiment 2
On Oct. 21, 1998, 18 pregnant heifers
at Gudmundsen Sandhills Laboratory
were stratified by weight and BCS and
randomly allotted to one of three supple-
mental treatments. Supplements were
the same as those described in Experi-
ment 1, and treatments were 1) heifers
supplemented to meet MP requirement
and receiving hay beginning in January
(MPS/Hay), 2) heifers supplemented
with conventional supplement and
receiving hay beginning in January
(CONT/Hay), and 3) heifers supple-
mented to meet MP requirement and
offered no hay during the experiment
(MPS/No Hay). Heifers were managed
on the same pasture described for
Experiment 1, with a stocking rate of
1.06 AUM/acre and an approximate
cumulative grazing pressure of .83
AUM/ton (adjusted for hay that was
fed). Hay was individually fed three times
weekly at the rate of 4 lbs/day beginning
Jan. 4, 1999. The amount was gradually
worked up to 6.5 lbs/day by the first of
February. The hay was late June har-
vested meadow hay containing 7.5% CP
and was 65.6% digestible (determined
by five day in-vivo trial with five year-
ling steers). Supplements were fed as
described in the first experiment. The
cattle were weighed twice weekly and
BCS every other month. Heifers were
weighed and BCS off-test on Feb. 20 and
21, 1999.
Results
Experiment 1
Heifers receiving the CONT supple-
ment lost 26 lb over the winter, but
heifers receiving the MPS treatment
gained 10 lb (Table 2; P = .04). Con-
sidering fetal weight (fetus, placenta,
fluids) was substantial during the time
the experiment was conducted, all heif-
Table 2. Weight, BCS, and forage intake (FI)
of heifers grazing winter Sandhills
range from October 1997 to February
1998 (Experiment 1).a
Item MPS CONT SDb
Beginning wt, lb 955 948 54
Final wt, lbc 965 921 49
Wt change, lbd 10 -26 27
Beginning BCS 6.4 6.3 .5
Final BCS 4.9 4.8 .3
BCS change 1.5 1.5 .7
November FI,e,f
lb 22.1 20.6 2.5
% BW 2.2 2.2 .2
January FI,e,f
lb 17.5 15.8 4.3
% BW 1.8 1.7 .4
February FI,e,f
lb 14.8 14.3 2.6
% BW 1.5 1.6 .3
aMPS: heifers supplemented to meet metabolizable
protein requirement; CONT: heifers supplemented
with conventional protein supplement. No hay fed
during the experiment.
bStandard deviation, n = 12.
cTreatments differ, P = .16.
dTreatments differ, P = .04.
eDry matter basis.
fIntake declined linearly over time (P = .0001).
ers lost body weight over the course of
the experiment. Figure 1 shows body
weights of each treatment group through-
out the experiment. Both treatment
groups gained weight from early Octo-
ber to late December, and during this
period the MPS heifers appeared to gain
weight faster than the CONT heifers. All
heifers lost weight in January and Febru-
Figure 1. Weight change of heifers in 1997-1998 (Exp. 1).
1060
1040
1020
1000
980
960
940
920
900
W
t, 
lb
MPS: R2=.83
CONT: R2=.66
10/2 10/17 11/1 11/16 12/1 12/16 12/31 1/15 1/30 2/14
Date, 1997-1998
Page 9 — 2000 Nebraska Beef Report
the MPS/Hay treatment had higher BCS
in February than those on the MPS/No
Hay treatment (5.7 versus 5.0; P = .01),
and tended to lose less BCS over the
course of the experiment (P = .10). Heif-
ers on the CONT/Hay treatment tended
to have higher BCS than the MPS/No
Hay treatment in February (5.4 versus
5.0; P = .10) and tended to lose less BCS
over the course of the experiment (P =
.16). With weight losses averaging 114
lbs for the MPS/No hay treatment com-
pared to 26 and 23 lb for the MPS/Hay
and CONT/Hay respectively, BCS dif-
ferences would be expected to be greater
between the hay and no hay treatments.
It is possible, however, that less rumen
fill in cattle on the MPS/No Hay treat-
ment could cause final weights to be
lower in this treatment relative to treat-
ments receiving hay.
The addition of MP to the hay-supple-
mented diets did not improve the heif-
ers’ ability to maintain weight or BCS
over conventional supplementation. The
addition of energy to low-quality rumi-
nant diets will increase MCP production
if adequate degradable protein is avail-
able. This increases the flow of MP to
the small intestine, and thus will decrease
the need for supplemental UIP. How-
ever, this may not fully explain the lack
of response to MP in Experiment 2 that
was noticed in Experiment 1. Yearly
variation in diet quality can be a factor.
Previous work in the Sandhills has
shown that diet quality can change rather
markedly between years (1998 Nebraska
Beef Report, pp. 20-21 ). This can cause
variation in intake and performance of
cattle. Figure 2 illustrates that all cattle
were losing weight until hay was fed to
the MPS/Hay and CONT/Hay groups.
Heifers were able to maintain body
weight when hay was fed while heifers
on the MPS/No Hay treatment contin-
ued to lose weight. This is unlike the
response noted in Experiment 1 where
cattle gained weight in the fall. When
energy is not limiting, one would expect
a growth response in the fall from sup-
plying UIP, before gestation require-
ments and environmental factors begin
to play a larger role in the winter months.
In Experiment 2, energy could have been
limiting performance in the fall. Reduced
Table 3. Weight and BCS of heifers grazing winter Sandhills range from October 1998 to
February 1999 (Experiment 2).a
Item MPS/Hay CONT/Hay MPS/No Hay SDb
Beginning Wt, lb 940 945 923 41
Final Wt, lbc 914 921 808 69
Wt change, lbd -26 -23 -114 48
Beginning BCS 6.1 6.0 6.1 .4
Final BCSe 5.7 5.4 5.0 .5
BCS changef -.4 -.6 -1.0 .6
aMPS/Hay: heifers supplemented to meet metabolizable protein requirements and fed hay (average 5 lb/
day) in January and February; CONT/Hay: heifers supplemented with conventional protein supplement
and fed hay in January and February; MPS/No Hay: heifers supplemented to meet metabolizable protein
requirements and fed no hay.
bStandard deviation, n = 18.
cMPS/Hay and CONT/Hay versus MPS/No Hay, P = .001.
dMPS/Hay and CONT/Hay versus MPS/No Hay, P = .0001.
eMPS/Hay versus MPS/No Hay, P = .01; CONT/Hay versus MPS/No Hay, P = .10.
fMPS/Hay versus MPS/No Hay, P = .10.
ary. It appears that MP was limiting
growth of the heifers during the fall,
while energy became first limiting in late
December. There were no differences in
BCS loss over the winter between the
MPS and CONT heifers (P=.83), with
both groups losing about 1.5 BCS. Most
of this condition loss (approximately
66%) occurred after late December, when
weights were declining.
Diets collected by the esophageally
fistulated cows during each intake pe-
riod had IVDMD averaging 52% in
November, 49% in January, and 50% in
February. Heifer FI was not different
between treatments when expressed as
lb/day or as a percentage of body weight
for any of the three intake periods (Table
2). However, FI declined linearly across
measurement dates (P = .0001). Heifer
FI averaged 21.4 lb/day (2.2 % of BW)
in November, 16.7 lb/day (1.8%) in Janu-
ary, and 14.5 lb/day (1.5%) in February.
The 1996 NRC model predicted the
heifers to have a DMI of 22 lb/day,
which was similar to the FI measured in
these heifers in November. However,
the NRC model did not predict a reduc-
tion in intake across the measurement
dates.
A reduction in the amount of forage
available for grazing and/or stressful
environmental conditions can cause
reductions in intake. In addition, heifer
intakes tend to decline as stage of gesta-
tion progresses and the fetus and fluids
begin to compress the rumen, which
reduces rumen volume. Because rumen
fill likely limits intake on low quality
diets, reduced rumen volume results in
lower intake. However, the decline in FI
over time measured in this study was
more severe than expected, and the 1.5%
of BW intakes measured in February
were much lower than intakes measured
in cows grazing similar Sandhills winter
range during late gestation. With actual
intakes used as inputs, the NRC model
predicted the heifers to lose .2 BCS in
November, .7 BCS in December, and
1.4 BCS in January. The heifers actually
lost .3 BCS in November, .5 BCS in
December, and .6 BCS in January. There-
fore, the actual performance was better
than predicted performance. However,
the November intake data yielded pre-
dicted BCS losses similar to actual when
modeled in the NRC. Sources of varia-
tion within actual and predicted BCS
estimates and the lack of performance
measurements in late February and early
March (the trial ended) could account
for the difference in NRC predicted per-
formance and actual heifer performance
in January (and early February). The
data show that heifer intakes declined as
stage of gestation increased. The decline
in intake prior to calving was more se-
vere than expected and predicted by the
NRC.
Experiment 2
There were no differences between
the MPS/Hay and the CONT/Hay in
body weight change nor BCS change
(Table 3). Heifers on the MPS/No Hay
treatment lost more weight over the
course of the winter than heifers on the
other treatments (P = .0001 ). Heifers on (Continued on next page)
2000 Nebraska Beef Report — Page 10
Figure 2. Weight change of heifers in 1998-1999 (Exp. 2).
975
950
925
900
875
850
825
800
W
t, 
lb
CON/Hay: R2=.45
MPS/No Hay: R2=.83
10/21 11/5 11/20 12/5 12/20 1/4 1/19 2/3 2/18
Date, 1998-1999
MPS/Hay: R2=.54
energy intake was likely due to forage
quality and/or the amount of forage avail-
able for grazing, as the grazing pressure
was higher in year two. This is further
supported by the fact that cattle on the
MPS/No Hay treatment, which was an
identical treatment to the MPS treatment
in Experiment 1, lost substantially more
weight in Experiment 2. Nevertheless,
body condition losses were less in
Experiment 2 than in Experiment 1.
Rumen-fill differences, error associated
with comparing BCS data on small
groups of animals across years and com-
position of weight-loss differences could
account for some of the year to year
variation.
In conclusion, heifers supplemented
with UIP (balanced MP requirement)
maintained more weight in the fall of one
year, but heifers did not respond to UIP
supplementation in the fall of a second
year. Year to year variation in forage
quality or availability, environment, or
other factors could have caused the year
differences. Heifer intakes declined as
stage of gestation increased. Managing
heifers on native range without feeding
hay resulted in large losses in body
weight.
1Trey Patterson, research technician, Animal
Science, Lincoln; Don Adams, professor, West
Central Research and Extension Center, North
Platte; Terry Klopfenstein, professor, Animal
Science, Lincoln; Jacki Musgrave, research
technician, Andy Applegarth, manager,
Gudmundsen Sandhills Laboratory, Whitman.


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Supplementing Metabolizable Protein to Yearling Heifers Grazing Winter Range

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