A finishing trial was conducted to evaluate phase-feeding of metabolizable protein in order to match requirements. Treatments were: 1) one finishing diet which matched requirements at initial weight; 2) one finishing diet which matched requirements at mid-weight; and 3) six finishing diets fed in sequential order which matched requirements throughout the feeding period. The 1996 Beef NRC was used to determine metabolizable protein requirements. No performance differences were observed. Gains and efficiencies were lower than projected, likely due to mud, causing protein requirements to be over-predicted. Phase-feeding metabolizable protein maintained equal performance and reduced nitrogen excretion compared to treatment 1

Cooper, Rob

Klopfenstein, Terry J.

Milton, Todd

English

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
Nebraska Beef Cattle Reports Animal Science Department 
January 2000 
Phase-feeding Metabolizable Protein for Finishing Steers 
Rob Cooper 
University of Nebraska-Lincoln 
Todd Milton 
University of Nebraska-Lincoln 
Terry J. Klopfenstein 
University of Nebraska-Lincoln, tklopfenstein1@unl.edu 
Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr 
 Part of the Animal Sciences Commons 
Cooper, Rob; Milton, Todd; and Klopfenstein, Terry J., "Phase-feeding Metabolizable Protein for Finishing 
Steers" (2000). Nebraska Beef Cattle Reports. 366. 
https://digitalcommons.unl.edu/animalscinbcr/366 
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 63 — 2000 Nebraska Beef Report
Phase-feeding Metabolizable Protein
for Finishing Steers
both the protein requirement for the ani-
mal as well as for the rumen microbial
population. Because the metabolizable
protein system more accurately predicts
protein requirements, it may be effica-
cious to feed protein levels at or near the
predicted requirement and still ensure
maximum performance.
The primary reason for feeding pro-
tein levels at, but not above, the require-
ment is pending environmental
regulations. In trials conducted at the
University of Nebraska (1999 Nebraska
Beef Report, pp. 60-63), yearling steers
were fed finishing diets containing 13.5%
crude protein, which was approximately
123% of the predicted requirement.
During the 137-day feeding period from
May to September, each steer excreted
approximately 65 pounds of nitrogen
onto the pen surface, of which about
71% volatilized into the air. In 192-day
calf-finishing trials conducted from
October to May, steers excreted approxi-
mately 71 lb of nitrogen onto the pen
surface, of which, approximately 41%
volatilized into the air.
The metabolizable protein system
(1996 NRC) predicts large changes in
the protein requirement throughout the
feeding period due to changes in intake,
body weight and composition of gain.
The overall MP requirement does not
change significantly; however, the com-
position or type of protein required does.
The degradable intake protein (DIP) re-
quirement increases due to a gradual
increase in intake. The undegradable
intake protein (UIP) requirement de-
creases due to both a larger supply of
microbial protein and from a lower re-
quirement because the composition of
gain is increasingly more fat and less
lean. Therefore, because the require-
ments are changing, a series of finishing
diets fed in sequential order in order to
meet, but not exceed both the DIP and
UIP requirements throughout the feed-
ing period (phase-feeding), should be
beneficial. Therefore, objectives of the
current trial were to evaluate phase-
feeding of metabolizable protein in or-
der to match requirements of finishing
calves.
Procedure
One hundred and fifty crossbred steer
calves (average initial weight = 585 lb)
were used in a completely randomized
design to evaluate phase-feeding of me-
tabolizable protein. Steers were strati-
fied by initial weight into one of 15 pens
(10 steers per pen). Pens were randomly
assigned to one of three treatments (five
pens per treatment). Treatments con-
sisted of: 1) one finishing diet fed
throughout the feeding period which was
formulated to match MP requirements at
700 lb body weight; 2) one finishing diet
fed throughout the feeding period which
was formulated to match MP require-
ments at 950 lb body weight; and 3) six
finishing diets fed in sequential order to
match MP requirements for every 100 lb
increment in body weight change
throughout the feeding period.
The 1996 NRC was used to deter-
mine the appropriate MP requirements.
In order to use the 1996 NRC model to
predict requirements throughout the feed-
ing period, accurate projections of body
weight, intake and gain are needed. We
summarized all appropriate calf finish-
ing trials conducted at the University of
Nebraska ARDC Feedlot. Using inter-
mediate weights, performance param-
eters for each 100 lb increment in body
weight were calculated and shown in
Table 1. These parameters were used as
inputs in the NRC model to formulate
the appropriate diets. Treatment 1 was
formulated for 700 lb which was the
initial weight of the steers when they
reached the finishing diet. Treatment 2
was formulated for 950 lb body weight
because it was the mid-weight of the
feeding period. Because the UIP require-
ment decreases during the feeding
period, treatment 1 should match the
UIP requirement initially, but then
Rob Cooper
Todd Milton
Terry Klopfenstein1
Phase-feeding metabolizable
protein can reduce nitrogen excre-
tion to the environment while main-
taining equal performance. In this
trial, performance was lower than
projected causing metabolizable
protein requirements to be
overpredicted.
Summary
A finishing trial was conducted to
evaluate phase-feeding of metaboliz-
able protein in order to match require-
ments. Treatments were: 1) one finishing
diet which matched requirements at ini-
tial weight; 2) one finishing diet which
matched requirements at mid-weight;
and 3) six finishing diets fed in sequen-
tial order which matched requirements
throughout the feeding period. The 1996
Beef NRC was used to determine
metabolizable protein requirements.
No performance differences were
observed. Gains and efficiencies were
lower than projected, likely due to mud,
causing protein requirements to be over-
predicted. Phase-feeding metabolizable
protein maintained equal performance
and reduced nitrogen excretion com-
pared to treatment 1.
Introduction
Typical feedlot diets often contain
higher crude protein levels than pre-
dicted by the 1984 NRC. This is prima-
rily because the factorial system (1984
NRC) does not account for the microbial
nitrogen requirement. Therefore, typi-
cal feedlot diets are formulated with
excessive crude protein levels in order to
ensure maximum performance.
The 1996 NRC uses a metabolizable
protein (MP) system which accounts for (Continued on next page)
2000 Nebraska Beef Report — Page 64
overfeed UIP increasingly throughout
the feeding period. Treatment 2 should
be deficient in UIP up to the midpoint
(950 lb), then become excessive for the
remainder of the feeding period. Treat-
ment 3 should match the UIP require-
ment throughout the feeding period. Our
hypothesis was that treatments 1 and 3
would perform similarly, and both would
perform greater than treatment 2. Treat-
ment 3 would be the most economical
because of less UIP supplementation
compared to treatment 1, and improved
performance compared to treatment 2.
Finishing diet compositions are shown
in Table 2. In treatment 3, because dry
rolled corn (60% UIP) and high mois-
ture corn (40% UIP) have opposite DIP
and UIP profiles, we altered the combi-
nation of these two ingredients in the six
finishing diets in order to match the
predicted requirements. Feathermeal and
bloodmeal were added in order to meet
UIP requirements beyond what dry rolled
corn could provide in diets A, B, and C.
The average dry matter percentages of
dry rolled and high moisture corn in the
six finishing diets of treatment 3, were
about the same as those used in the
finishing diets of treatments 1 and 2. All
finishing diets were formulated to con-
tain a minimum of .7% calcium, .3%
phosphorus, .8% potassium, 27 g/ton
Rumensin, and 10 g/ton Tylan (DM
basis). Steers were brought up to full-
feed in 21 days using four step-up diets
containing 45, 35, 25, 15% alfalfa (DM
basis).
Steers were weighed initially after
being limit-fed at 2% of body weight for
five days to minimize differences in gut
fill. Steers were implanted with Revalor
S on days 1 and 85 and fed for a total of
203 days. Final weights were calculated
using hot carcass weight adjusted to a
common dressing percentage (62%).
Results
Results are shown in Table 3. No
differences were observed (P > .10) for
any performance or carcass parameters
for treatments 1, 2, or 3. Based on past
feeding experience with similar calves
and diets, we projected these steers to
consume 21 lb of feed and gain about 3.6
lb/day (Table 1). The steers in this trial
Table 1. University of Nebraska-Lincoln Feedlot performance parameters for finishing calves.
Body weight DM intake DM intake Daily gain Feed/Gain
lb lb/d % of body weight lb/d
  600 18.0 3.00 3.6 5.0
  700 19.0 2.71 3.6 5.3
  800 20.0 2.50 3.6 5.6
  900 21.0 2.33 3.6 5.8
1000 21.5 2.15 3.6 6.0
1100 22.0 2.00 3.6 6.1
1200 22.5 1.88 3.6 6.3
1300 23.0 1.77 3.6 6.4
Average   950 20.9 2.29 3.6 5.8
Table 2. Composition of finishing diets (% of diet DM).
Treatmenta
1 2 3
A B C D E F
Dry rolled corn 46 46 67 67 67 29 20 14
High moisture corn 21 21 — — — 38 47 55
Wet corn gluten feed 20 20 20 20 20 20 20 20
Alfalfa 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5
Dry supplement 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5
Feathermeal 1.32 .12 1.04 .96 .20 — — —
Bloodmeal .33 .03 .26 .24 .05 — — —
Crude protein 12.7 11.7 12.7 12.6 12.0 11.4 11.3 11.2
aTreatment 1 was balanced for initial weight, Treatment 2 was balanced for the mid-weight, and diets in
Treatment 3 were fed in sequential order and balanced for every 100 lb increment in body weight.
Table 3. Performance, carcass, and nitrogen balance results.
Treatment
1 2 3 P =
DM intake, lb 21.2 20.9 21.0 .69
Daily gain, lb 3.29 3.20 3.21 .21
Feed/gain 6.45 6.54 6.54 .30
Fat depth, in. .49 .50 .48 .79
Marbling scoreb 505 506 503 .98
Yield grade 2.4 2.2 2.2 .27
Nitrogen intake, lb/head 87.2c 79.4d 80.5d .0001
Nitrogen retentionf, lb/head 10.7c 10.5d 10.5d .03
Nitrogen excretiong, lb/head 76.6c 68.9d 70.0d .0001
aTreatment 1 was balanced for initial weight, Treatment 2 was balanced for the mid-weight, and diets in
Treatment 3 were fed in sequential order and balanced for every 100 lb increment in body weight.
bMarbling score of 500 = Small 0, 600 = Modest 0.
cdMeans in a row not bearing a common superscript differ (P < .05).
fNitrogen retention based on ADG, NRC equation for retained energy and retained protein.
gNitrogen excretion calculated as intake minus retention.
consumed the amount we projected, but
only gained about 3.2 lb/day. This trial
was conducted during the winter and
spring of 97-98. During this period, we
experienced very poor feeding con-
ditions with a lot of mud. It is our
conclusion that the mud increased the
steers’ NEm requirement, increasing
feed required per lb of gain by approxi-
mately 12%. Because gains were lower
than expected, MP requirements were
overpredicted. Treatment 2 provided
Page 65 — 2000 Nebraska Beef Report
the lowest level of supplemental UIP
and should have been deficient during
the first half of the feeding period, based
on our projections. However, the actual
UIP balance was positive during the
entire feeding period for treatment 2, as
well as for the treatments 1 and 3. There-
fore, no performance differences would
be expected.
Due to performance lower than pro-
jected, the results of this study do not
properly evaluate phase-feeding of MP.
Analysis with the 1996 NRC model
agrees with the performance data in that
the model predicts no response because
all treatments were excessive in UIP and
MP. However, there was a treatment
difference in nitrogen excretion onto the
pen surface. Treatment 1 consumed and
excreted more nitrogen (P < .05) than
treatments 2 or 3 (Table 3). As a result,
treatment 1 not only had the highest
ration cost, but also poses the greatest
environmental concern. In this trial, treat-
ment 2 was optimal because of lowest
protein supplementation cost with equal
performance. However, we would
project under good feeding conditions,
the performance of treatment 2 would be
reduced compared to treatments 1 and 3.
This trial emphasizes the need for
accurate predictions of performance in
order to match MP requirements. Opti-
mizing protein supplementation in order
to minimize excretion and maintain
maximum performance will become a
very important issue for cattle feeding.
Phase-feeding of MP throughout the
feeding period may be efficacious;
however, additional research is needed
to validate this concept.
1Rob Cooper, research technician; Terry
Klopfenstein, professor; Todd Milton, assistant
professor, Animal Science, Lincoln.


Phase-feeding Metabolizable Protein for Finishing Steers

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Nebraska Beef Cattle Reports Animal Science Department January 2000 Phase-feeding Metabolizable Protein for Finishing Steers Rob Cooper University of Nebraska-Lincoln Todd Milton University of Nebraska-Lincoln Terry J. Klopfenstein University of Nebraska-Lincoln, tklopfenstein1@unl.edu Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr  Part of the Animal Sciences Commons Cooper, Rob; Milton, Todd; and Klopfenstein, Terry J., "Phase-feeding Metabolizable Protein for Finishing Steers" (2000). Nebraska Beef Cattle Reports. 366. https://digitalcommons.unl.edu/animalscinbcr/366 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 63 — 2000 Nebraska Beef ReportPhase-feeding Metabolizable Proteinfor Finishing Steersboth the protein requirement for the ani-mal as well as for the rumen microbialpopulation. Because the metabolizableprotein system more accurately predictsprotein requirements, it may be effica-cious to feed protein levels at or near thepredicted requirement and still ensuremaximum performance.The primary reason for feeding pro-tein levels at, but not above, the require-ment is pending environmentalregulations. In trials conducted at theUniversity of Nebraska (1999 NebraskaBeef Report, pp. 60-63), yearling steerswere fed finishing diets containing 13.5%crude protein, which was approximately123% of the predicted requirement.During the 137-day feeding period fromMay to September, each steer excretedapproximately 65 pounds of nitrogenonto the pen surface, of which about71% volatilized into the air. In 192-daycalf-finishing trials conducted fromOctober to May, steers excreted approxi-mately 71 lb of nitrogen onto the pensurface, of which, approximately 41%volatilized into the air.The metabolizable protein system(1996 NRC) predicts large changes inthe protein requirement throughout thefeeding period due to changes in intake,body weight and composition of gain.The overall MP requirement does notchange significantly; however, the com-position or type of protein required does.The degradable intake protein (DIP) re-quirement increases due to a gradualincrease in intake. The undegradableintake protein (UIP) requirement de-creases due to both a larger supply ofmicrobial protein and from a lower re-quirement because the composition ofgain is increasingly more fat and lesslean. Therefore, because the require-ments are changing, a series of finishingdiets fed in sequential order in order tomeet, but not exceed both the DIP andUIP requirements throughout the feed-ing period (phase-feeding), should bebeneficial. Therefore, objectives of thecurrent trial were to evaluate phase-feeding of metabolizable protein in or-der to match requirements of finishingcalves.ProcedureOne hundred and fifty crossbred steercalves (average initial weight = 585 lb)were used in a completely randomizeddesign to evaluate phase-feeding of me-tabolizable protein. Steers were strati-fied by initial weight into one of 15 pens(10 steers per pen). Pens were randomlyassigned to one of three treatments (fivepens per treatment). Treatments con-sisted of: 1) one finishing diet fedthroughout the feeding period which wasformulated to match MP requirements at700 lb body weight; 2) one finishing dietfed throughout the feeding period whichwas formulated to match MP require-ments at 950 lb body weight; and 3) sixfinishing diets fed in sequential order tomatch MP requirements for every 100 lbincrement in body weight changethroughout the feeding period.The 1996 NRC was used to deter-mine the appropriate MP requirements.In order to use the 1996 NRC model topredict requirements throughout the feed-ing period, accurate projections of bodyweight, intake and gain are needed. Wesummarized all appropriate calf finish-ing trials conducted at the University ofNebraska ARDC Feedlot. Using inter-mediate weights, performance param-eters for each 100 lb increment in bodyweight were calculated and shown inTable 1. These parameters were used asinputs in the NRC model to formulatethe appropriate diets. Treatment 1 wasformulated for 700 lb which was theinitial weight of the steers when theyreached the finishing diet. Treatment 2was formulated for 950 lb body weightbecause it was the mid-weight of thefeeding period. Because the UIP require-ment decreases during the feedingperiod, treatment 1 should match theUIP requirement initially, but thenRob CooperTodd MiltonTerry Klopfenstein1Phase-feeding metabolizableprotein can reduce nitrogen excre-tion to the environment while main-taining equal performance. In thistrial, performance was lower thanprojected causing metabolizableprotein requirements to beoverpredicted.SummaryA finishing trial was conducted toevaluate phase-feeding of metaboliz-able protein in order to match require-ments. Treatments were: 1) one finishingdiet which matched requirements at ini-tial weight; 2) one finishing diet whichmatched requirements at mid-weight;and 3) six finishing diets fed in sequen-tial order which matched requirementsthroughout the feeding period. The 1996Beef NRC was used to determinemetabolizable protein requirements.No performance differences wereobserved. Gains and efficiencies werelower than projected, likely due to mud,causing protein requirements to be over-predicted. Phase-feeding metabolizableprotein maintained equal performanceand reduced nitrogen excretion com-pared to treatment 1.IntroductionTypical feedlot diets often containhigher crude protein levels than pre-dicted by the 1984 NRC. This is prima-rily because the factorial system (1984NRC) does not account for the microbialnitrogen requirement. Therefore, typi-cal feedlot diets are formulated withexcessive crude protein levels in order toensure maximum performance.The 1996 NRC uses a metabolizableprotein (MP) system which accounts for (Continued on next page)2000 Nebraska Beef Report — Page 64overfeed UIP increasingly throughoutthe feeding period. Treatment 2 shouldbe deficient in UIP up to the midpoint(950 lb), then become excessive for theremainder of the feeding period. Treat-ment 3 should match the UIP require-ment throughout the feeding period. Ourhypothesis was that treatments 1 and 3would perform similarly, and both wouldperform greater than treatment 2. Treat-ment 3 would be the most economicalbecause of less UIP supplementationcompared to treatment 1, and improvedperformance compared to treatment 2.Finishing diet compositions are shownin Table 2. In treatment 3, because dryrolled corn (60% UIP) and high mois-ture corn (40% UIP) have opposite DIPand UIP profiles, we altered the combi-nation of these two ingredients in the sixfinishing diets in order to match thepredicted requirements. Feathermeal andbloodmeal were added in order to meetUIP requirements beyond what dry rolledcorn could provide in diets A, B, and C.The average dry matter percentages ofdry rolled and high moisture corn in thesix finishing diets of treatment 3, wereabout the same as those used in thefinishing diets of treatments 1 and 2. Allfinishing diets were formulated to con-tain a minimum of .7% calcium, .3%phosphorus, .8% potassium, 27 g/tonRumensin, and 10 g/ton Tylan (DMbasis). Steers were brought up to full-feed in 21 days using four step-up dietscontaining 45, 35, 25, 15% alfalfa (DMbasis).Steers were weighed initially afterbeing limit-fed at 2% of body weight forfive days to minimize differences in gutfill. Steers were implanted with RevalorS on days 1 and 85 and fed for a total of203 days. Final weights were calculatedusing hot carcass weight adjusted to acommon dressing percentage (62%).ResultsResults are shown in Table 3. Nodifferences were observed (P > .10) forany performance or carcass parametersfor treatments 1, 2, or 3. Based on pastfeeding experience with similar calvesand diets, we projected these steers toconsume 21 lb of feed and gain about 3.6lb/day (Table 1). The steers in this trialTable 1. University of Nebraska-Lincoln Feedlot performance parameters for finishing calves.Body weight DM intake DM intake Daily gain Feed/Gainlb lb/d % of body weight lb/d  600 18.0 3.00 3.6 5.0  700 19.0 2.71 3.6 5.3  800 20.0 2.50 3.6 5.6  900 21.0 2.33 3.6 5.81000 21.5 2.15 3.6 6.01100 22.0 2.00 3.6 6.11200 22.5 1.88 3.6 6.31300 23.0 1.77 3.6 6.4Average   950 20.9 2.29 3.6 5.8Table 2. Composition of finishing diets (% of diet DM).Treatmenta1 2 3A B C D E FDry rolled corn 46 46 67 67 67 29 20 14High moisture corn 21 21 — — — 38 47 55Wet corn gluten feed 20 20 20 20 20 20 20 20Alfalfa 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5Dry supplement 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5Feathermeal 1.32 .12 1.04 .96 .20 — — —Bloodmeal .33 .03 .26 .24 .05 — — —Crude protein 12.7 11.7 12.7 12.6 12.0 11.4 11.3 11.2aTreatment 1 was balanced for initial weight, Treatment 2 was balanced for the mid-weight, and diets inTreatment 3 were fed in sequential order and balanced for every 100 lb increment in body weight.Table 3. Performance, carcass, and nitrogen balance results.Treatment1 2 3 P =DM intake, lb 21.2 20.9 21.0 .69Daily gain, lb 3.29 3.20 3.21 .21Feed/gain 6.45 6.54 6.54 .30Fat depth, in. .49 .50 .48 .79Marbling scoreb 505 506 503 .98Yield grade 2.4 2.2 2.2 .27Nitrogen intake, lb/head 87.2c 79.4d 80.5d .0001Nitrogen retentionf, lb/head 10.7c 10.5d 10.5d .03Nitrogen excretiong, lb/head 76.6c 68.9d 70.0d .0001aTreatment 1 was balanced for initial weight, Treatment 2 was balanced for the mid-weight, and diets inTreatment 3 were fed in sequential order and balanced for every 100 lb increment in body weight.bMarbling score of 500 = Small 0, 600 = Modest 0.cdMeans in a row not bearing a common superscript differ (P < .05).fNitrogen retention based on ADG, NRC equation for retained energy and retained protein.gNitrogen excretion calculated as intake minus retention.consumed the amount we projected, butonly gained about 3.2 lb/day. This trialwas conducted during the winter andspring of 97-98. During this period, weexperienced very poor feeding con-ditions with a lot of mud. It is ourconclusion that the mud increased thesteers’ NEm requirement, increasingfeed required per lb of gain by approxi-mately 12%. Because gains were lowerthan expected, MP requirements wereoverpredicted. Treatment 2 providedPage 65 — 2000 Nebraska Beef Reportthe lowest level of supplemental UIPand should have been deficient duringthe first half of the feeding period, basedon our projections. However, the actualUIP balance was positive during theentire feeding period for treatment 2, aswell as for the treatments 1 and 3. There-fore, no performance differences wouldbe expected.Due to performance lower than pro-jected, the results of this study do notproperly evaluate phase-feeding of MP.Analysis with the 1996 NRC modelagrees with the performance data in thatthe model predicts no response becauseall treatments were excessive in UIP andMP. However, there was a treatmentdifference in nitrogen excretion onto thepen surface. Treatment 1 consumed andexcreted more nitrogen (P < .05) thantreatments 2 or 3 (Table 3). As a result,treatment 1 not only had the highestration cost, but also poses the greatestenvironmental concern. In this trial, treat-ment 2 was optimal because of lowestprotein supplementation cost with equalperformance. However, we wouldproject under good feeding conditions,the performance of treatment 2 would bereduced compared to treatments 1 and 3.This trial emphasizes the need foraccurate predictions of performance inorder to match MP requirements. Opti-mizing protein supplementation in orderto minimize excretion and maintainmaximum performance will become avery important issue for cattle feeding.Phase-feeding of MP throughout thefeeding period may be efficacious;however, additional research is neededto validate this concept.1Rob Cooper, research technician; TerryKlopfenstein, professor; Todd Milton, assistantprofessor, Animal Science, Lincoln.

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Phase-feeding Metabolizable Protein for Finishing Steers

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