A metabolism trial was conducted in finishing heifers to determine if allantoin in spot urine samples could be a predictor of microbial CP (MCP) supply. When corn bran replaced high moisture corn, ruminal pH was higher and microbial efficiency and flow were greater. Estimated microbial efficiency and flow were not different for SBM compared to urea as a source of degradable protein. Daily variation in intake was reflected in MCP estimates. Within day variation for MCP estimates was consistent and small. Estimates of MCP from allantoin in spot urine samples followed NRC estimates. Results demonstrate that allantoin is an effective predictor of MCP flow

Erickson, Galen E.

Klopfenstein, Terry J.

Loy, Tim W.

McDonald, R. Allen

Whittet, Kimberly M.

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Nebraska Beef Cattle Reports Animal Science Department January 2004 Effects of Corn Bran and Degradable Protein Source on Microbial Protein Estimated From Spot Urine Samples in Heifers R. Allen McDonald University of Nebraska-Lincoln Terry J. Klopfenstein University of Nebraska-Lincoln, tklopfenstein1@unl.edu Galen E. Erickson University of Nebraska-Lincoln, gerickson4@unl.edu Tim W. Loy University of Nebraska-Lincoln Kimberly M. Whittet University of Nebraska-Lincoln Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr  Part of the Animal Sciences Commons McDonald, R. Allen; Klopfenstein, Terry J.; Erickson, Galen E.; Loy, Tim W.; and Whittet, Kimberly M., "Effects of Corn Bran and Degradable Protein Source on Microbial Protein Estimated From Spot Urine Samples in Heifers" (2004). Nebraska Beef Cattle Reports. 202. https://digitalcommons.unl.edu/animalscinbcr/202 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. 2004 Nebraska Beef Report — Page 28Effects of Corn Bran and Degradable ProteinSource on Microbial Protein Estimated FromSpot Urine Samples in Heifersbetween allantoin excretion andpurine flow to the duodenum. Pre-vious research analyzed urinesamples from total daily collections.This technique is noninvasive butis still laborious and limits cattlenumbers because it requires totalcollection. Creatinine may be usedas a marker of urine volumebecause it is excreted at a constantrate relative to body weight. Usingcreatinine, spot sampling of urinecould be used in a larger number ofcattle in typical production settings.Our primary objective was to feeddiets that would create differencesin MCP supply and determine ifallantoin to creatinine ratios in spoturine samples could predict thesedifferences.ProcedureSix ruminally cannulated cross-bred yearling heifers (1311 + 103 lbBW) were used in a 3 x 6 Latinrectangle. Each of three periodsconsisted of 9 day for adaptation todiet and 5 day for collection. Basediets (Table 1) were a high-moisturecorn (HMC) diet and a diet withcorn bran (BRAN) replacing 20%(DM basis) HMC. Urea was addedto base diets at 0.9% of diet DM.Addition of corn bran provided ahighly digestible fiber source thatwas expected to increase ruminalpH and subsequently increasemicrobial efficiency and flow. TheBRAN diet also was fed with 7.8%soybean meal (SBM) (DM basis)replacing HMC. The levels of ureaand SBM were calculated to pro-vide equal amounts of degrableintake protein (DIP). The SBM dietwas included to provide microbes asource of true protein and aminoacids that was not available whenusing urea as the supplemental DIPsource. The hypothesis was thattrue protein and amino acidswould increase microbial efficiencyresulting in increased MCP flow.Heifers were fed for ad libitumR. Allen McDonaldTerry J. KlopfensteinGalen E. EricksonTim W. LoyKimberly M. Whittet1SummaryA metabolism trial was conductedin finishing heifers to determine ifallantoin in spot urine samples couldbe a predictor of microbial CP (MCP)supply. When corn bran replaced highmoisture corn, ruminal pH was higherand microbial efficiency and flow weregreater. Estimated microbial efficiencyand flow were not different for SBMcompared to urea as a source of degrad-able protein. Daily variation in intakewas reflected in MCP estimates.Within day variation for MCP esti-mates was consistent and small. Esti-mates of MCP from allantoin in spoturine samples followed NRC estimates.Results demonstrate that allantoin isan effective predictor of MCP flow.IntroductionPurines are one of the buildingblocks used in the synthesis ofDNA and RNA. Feed purines areessentially totally degraded in therumen leaving only purines ofmicrobial origin for passage to theduodenum. Therefore, purines havecommonly been used to estimatemicrobial crude protein (MCP) flowin studies assessing protein statusof beef cattle. However, this requiresduodenal fistulation resulting inlaborious experiments with fewcattle. Urinary allantoin is derivedfrom the breakdown of purines.Recent research (2001 NebraskaBeef Report, pp. 115-116) hasshown a strong linear relationshipTable 1. Composition of finishing diets (% of DM).DietaIngredient HMC BRAN SBMHigh-moisture corn 88.3 68.3 60.5Corn bran — 20.0 20.0Soybean meal — — 7.8Cottonseed hulls 6.7 6.7 6.7Dry supplementb 5.0 5.0 5.0Fine ground milo 1.68 1.67 2.98Limestone 1.50 1.49 1.36Urea 0.90 0.90 —Potassium Chloride 0.43 0.45 0.17Salt 0.30 0.30 0.30Tallow 0.10 0.10 0.10Trace mineral premix 0.05 0.05 0.05Rumensin premix 0.02 0.02 0.02Tylan premix 0.01 0.01 0.01Vitamin premix 0.01 0.01 0.01aHMC=high-moisture corn diet, BRAN=corn bran diet, SBM=soybean meal diet.bAll diets supplemented to contain a minimum of 0.6% Ca, 0.24% P, 0.6% K, and 0.1% S(DM basis). All diets contained 32 g/ton monensin and 11 g/ton tylosin (DM basis).Page 29 — 2004 Nebraska Beef Reportcollection day at 0800, 1100, 1400,and 1700. The molar ratio ofallantoin to creatinine was calcu-lated for each urine sample. Weassumed daily urinary creatinineoutput was equal to 16.4 mg/lbBW. To calculate daily allantoinoutput (moles/day), the allantoin tocreatinine ratio was multiplied byassumed daily creatinine output.Estimated MCP flow was calcu-lated from daily allantoin outputaccording to equations outlinedpreviously (2002 Nebraska BeefReport, pp. 66-68). Estimates ofmicrobial efficiency (g/lb DM) werecalculated by dividing estimatedMCP supply by digestible DMI.Data were analyzed as repeatedmeasures using the Mixed proce-dure of SAS. For intake and ruminalpH analyses, collection day repre-sented repeated observations. Forurine data analyses, collection dayand time of collection were therepeated observations. To deter-mine the effect of corn bran addi-tion, a contrast was used tocompare the HMC diet to both ofthe corn bran containing diets. Todetermine the effect of supplemen-tal DIP source, a contrast was usedto compare the BRAN and SBMdiets. Additionally, linear and qua-dratic effects of time and day weretested with orthogonal contrasts.The REG procedure of SAS wasused to compare MCP estimatesfrom urinary allantoin to estimatesfrom Level 1 of the NRC (1996)model.ResultsRuminal pH below 5.6 is gener-ally used to define subacute acido-sis. Results of the current trialindicate the presence of subacuteacidosis. Heifers consuming theHMC diet had an average ruminalpH of 5.44 (Table 2). Additionally,those heifers spent almost 15 hoursof each 24-hour collection below apH of 5.6 (Table 2). Intakes werevariable and treatment and collec-tion day interacted (P<0.01) withTable 2. Effect of HMC replacement with corn bran or supplemental degradableprotein source on digestion, ruminal pH, and microbial estimates.Dieta ContrastsbItem HMC BRAN SBM SEM 1 2DMI, lb/day 22.2 25.1 23.8 1.5 0.14 0.35Digestible DMI, lb/day 18.7 20.5 18.7 1.3 0.49 0.22Ruminal pH 5.44 5.78 5.88 0.18 0.01 0.46Time pH below 5.6, min 887 576 428 212 0.09 0.49A:Cc 1.05 1.30 1.23 0.09 0.02 0.38Urine volume, L/dayd 31.6 32.2 25.8 9.4 0.71 0.38MCP, g/daye 740 966 913 88 0.02 0.47Microbial efficiencyf 38.8 46.0 48.6 4.0 0.05 0.54aHMC=high-moisture corn diet, BRAN=corn bran diet, SBM=soybean meal diet.bContrast 1 is comparison of HMC to average of both corn bran containing diets;Contrast 2 is comparison of BRAN and SBM.cMolar ratio of allantoin to creatinine.dUrine volume calculated from creatinine output.eMicrobial crude protein.fMicrobial efficiency calculated as g MCP/lb digestible DMI.(Continued on next page)intake once daily at 0900. Chromicoxide was used as an indigestiblemarker to calculate total-tract diges-tion and was administered throughthe ruminal cannula twice daily at0800 and 1700. Feed intake andruminal pH were monitored con-tinuously with feed weight andruminal pH recorded every minuteduring the 5 day collection period.Spot urine and fecal grabsamples were obtained on eachFigure 1. Daily variation in dry matter intake. SEM=1.5. Treatment x day (P<0.01).Linear effect of day within HMC (P=0.19). Linear effect of day withinBRAN (P<0.01). Linear effect of day within SBM (P=0.13). Differences inmeans on a particular sampling day are denoted by letters beneath points:a Contrast comparing HMC to both corn bran containing diets (P<0.10) andb Contrast comparing BRAN and SBM (P<0.10).302520151050DMI, lb/dayHMCBRANSBMLinear (HMC)Linear (BRAN)Linear (SBM)1 2 3 4 5Day of Collection Periodb a ab ab2004 Nebraska Beef Report — Page 30DMI increasing linearly (P<0.01) forthe BRAN diet (Figure 1). This maybe an indication that the adaptationperiod was not long enough. Thesignificance of differences in DMIfor HMC compared to corn brancontaining diets increased towardthe end of the collection period(day 3, P=0.09; day 4, P=0.08; day 5,P=0.04).Estimates of MCP flow andmicrobial efficiency from allantointo creatinine ratios in spot urinesamples followed the pH andintake responses for dietary addi-tion of corn bran. Treatment effectsfor estimates of MCP interactedwith collection day (P=0.02), andMCP was lower on day 2 (P=0.02),day 4 (P=0.01), and day 5 (P<0.01)for HMC versus the average of thecorn bran containing diets (Figure2). On average, corn bran additionincreased MCP estimates by 27%(P=0.02; Table 2). The interactionfor MCP estimates is explained bythe interaction found for intake.When intake variation was takeninto account by calculating micro-bial efficiency, the interaction wasno longer present (P=0.28), andthere was no main effect of collec-tion day. However, microbial effi-ciency increased (P=0.05) by 22%with corn bran addition (Table 2).Because there were no differencesin digestible DMI (Table 2), thelower MCP value for HMC is attrib-utable to lower microbial efficiencyas a result of lower ruminal pH.The present study also was de-signed to evaluate supplementingSBM versus urea based on the hy-pothesis that providing microbes asource of true protein and aminoacids would increase microbial effi-ciency and flow. There was noeffect on DMI, digestible DMI, orruminal pH when SBM was sup-plemented relative to urea (Table 2).Evaluation of the treatment by col-lection day interactions discussedpreviously for intake (Figure 1)showed that DMI was higher forSBM relative to BRAN on day 1(P=0.05) and lower on day 4(P=0.05), and day 5 (P=0.03). Evalu-Figure 2. Daily variation in microbial protein estimates. SEM=103. Treatment x day(P=0.02). Linear effect of day within HMC (P=0.01). Linear effect of daywithin BRAN (P<0.01). Linear effect of day within SBM (P=0.45).Differences in means on a particular sampling day are denoted by lettersbeneath points: a contrast comparing HMC to both corn bran containingdiets (P<0.10) and b contrast comparing BRAN and SBM (P<0.10).120010008006004002000MCP, g/daya    a     abHMCBRANSBMLinear (HMC)Linear (BRAN)Linear (SBM)1 2 3 4 5Day of collection periodFigure 3. Diurnal variation in microbial protein estimates. SEM=75. Treatment xtime (P=0.19). Main effect of time (P=0.10). Linear effect of time (P=0.06).120010008006004002000MCP, g/day0800 1100 1400 1700Time of dayation of the treatment by collectionday interaction for MCP estimates(Figure 2) indicates that MCP washigher (P=0.05) only on day 5 of thecollection period for BRAN com-pared to SBM. Microbial efficiencydid not differ between SBM andBRAN (Table 2) treatments. Theseresults are in conflict with someprevious reports that indicatedMCP flow and efficiency werehigher for SBM versus urea supple-Page 31 — 2004 Nebraska Beef Reportmented diets. However, those trialswere conducted with DRC-basedfinishing diets, and it seems plau-sible that the higher DIP value forHMC relative to DRC would pro-vide microbes with more true pro-tein and amino acids decreasingthe response to SBM as a supple-mental DIP source. Additionally,this trial compared SBM and ureain corn bran containing diets whererisk of acidosis had been reduced.Estimates of urine volume(L/day) did not differ with treat-ment and were comparable to esti-mates found in other research trials.The allantoin to creatinine ratiowas only different (P=0.02) whencomparing HMC to the corn brancontaining diets representing theincreased MCP flow. Some previousstudies have found allantoin tocreatinine ratios and estimates ofMCP display diurnal variability.This variability is acceptable aslong as it is consistent and predict-able. Our most important finding inthis regard is that there was no timeof day by collection day interactionfor estimates of MCP (P=0.22). Wedid show some diurnal variabilitywith a MCP estimates increasinglinearly (P=0.06) from 0800 to 1700(Figure 3). However, MCP estimatesonly increased by 63 g or 7% fromthe first sampling time to the last. Inaddition, there was no treatment xtime of day interaction for MCPestimates. Using an assumedcreatinine output of 16.4 mg/lb BWresulted in MCP estimates that werein agreement with estimates fromthe NRC (1996) model (Figure 4).In conclusion, we observed anincrease in MCP flow and efficiencyestimated from allantoin excretionin spot urine samples when aver-age ruminal pH was increased byadding corn bran to HMC-basedfinishing diets. Additionally, therewere no differences in ruminal pH,intake, or digestibility between dietscontaining corn bran that weresupplemented with urea or SBMresulting in no differences in MCPflow or efficiency. There was littlediurnal variation in MCP estimates,and daily variation due to changesin intake was removed when micro-bial efficiency was calculated. Esti-mates of MCP followed NRC (1996)estimates, but creatinine outputsmay need to be adjusted on an indi-vidual animal basis to more accu-rately and precisely estimate MCP.This trial was conducted in ametabolism setting with a smallnumber of animals. However, thegoal of developing a spot samplingtechnique is to be capable of sam-pling large numbers of animals in amore typical production setting.Results of a companion finishingtrial are also reported in this publi-cation (pp. 32). In that trial, 120head of heifers were fed the samediets and spot sampled across thefeeding period.1R. Allen McDonald, graduatestudent; Terry J. Klopfenstein, professor,Lincoln; Galen E. Erickson, assistantprofessor, Lincoln; Tim W. Loy, researchtechnician; Kimberly M. Whittet,laboratory supervisor, Lincoln.16001400120010008006004002000MCP, g/dayy = 0.71x + 192.08R2 = 0.59IsoplethaLinear Regression  0    200 400 600 800    1000  1200  1400 1600MCP estimated from NRC, g/dFigure 4. Relationship between allantoin and NRC estimates of microbial protein. aIsopleth is the line where estimates are equal and r2 is equal to 1.Intercept (SE=161; P=0.25). Slope (SE=0.16; P<0.01).

Effects of Corn Bran and Degradable Protein Source on Microbial Protein Estimated From Spot Urine Samples in Heifers

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
Nebraska Beef Cattle Reports Animal Science Department 
January 2004 
Effects of Corn Bran and Degradable Protein Source on Microbial 
Protein Estimated From Spot Urine Samples in Heifers 
R. Allen McDonald 
University of Nebraska-Lincoln 
Terry J. Klopfenstein 
University of Nebraska-Lincoln, tklopfenstein1@unl.edu 
Galen E. Erickson 
University of Nebraska-Lincoln, gerickson4@unl.edu 
Tim W. Loy 
University of Nebraska-Lincoln 
Kimberly M. Whittet 
University of Nebraska-Lincoln 
Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr 
 Part of the Animal Sciences Commons 
McDonald, R. Allen; Klopfenstein, Terry J.; Erickson, Galen E.; Loy, Tim W.; and Whittet, Kimberly M., 
"Effects of Corn Bran and Degradable Protein Source on Microbial Protein Estimated From Spot Urine 
Samples in Heifers" (2004). Nebraska Beef Cattle Reports. 202. 
https://digitalcommons.unl.edu/animalscinbcr/202 
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. 
2004 Nebraska Beef Report — Page 28
Effects of Corn Bran and Degradable Protein
Source on Microbial Protein Estimated From
Spot Urine Samples in Heifers
between allantoin excretion and
purine flow to the duodenum. Pre-
vious research analyzed urine
samples from total daily collections.
This technique is noninvasive but
is still laborious and limits cattle
numbers because it requires total
collection. Creatinine may be used
as a marker of urine volume
because it is excreted at a constant
rate relative to body weight. Using
creatinine, spot sampling of urine
could be used in a larger number of
cattle in typical production settings.
Our primary objective was to feed
diets that would create differences
in MCP supply and determine if
allantoin to creatinine ratios in spot
urine samples could predict these
differences.
Procedure
Six ruminally cannulated cross-
bred yearling heifers (1311 + 103 lb
BW) were used in a 3 x 6 Latin
rectangle. Each of three periods
consisted of 9 day for adaptation to
diet and 5 day for collection. Base
diets (Table 1) were a high-moisture
corn (HMC) diet and a diet with
corn bran (BRAN) replacing 20%
(DM basis) HMC. Urea was added
to base diets at 0.9% of diet DM.
Addition of corn bran provided a
highly digestible fiber source that
was expected to increase ruminal
pH and subsequently increase
microbial efficiency and flow. The
BRAN diet also was fed with 7.8%
soybean meal (SBM) (DM basis)
replacing HMC. The levels of urea
and SBM were calculated to pro-
vide equal amounts of degrable
intake protein (DIP). The SBM diet
was included to provide microbes a
source of true protein and amino
acids that was not available when
using urea as the supplemental DIP
source. The hypothesis was that
true protein and amino acids
would increase microbial efficiency
resulting in increased MCP flow.
Heifers were fed for ad libitum
R. Allen McDonald
Terry J. Klopfenstein
Galen E. Erickson
Tim W. Loy
Kimberly M. Whittet1
Summary
A metabolism trial was conducted
in finishing heifers to determine if
allantoin in spot urine samples could
be a predictor of microbial CP (MCP)
supply. When corn bran replaced high
moisture corn, ruminal pH was higher
and microbial efficiency and flow were
greater. Estimated microbial efficiency
and flow were not different for SBM
compared to urea as a source of degrad-
able protein. Daily variation in intake
was reflected in MCP estimates.
Within day variation for MCP esti-
mates was consistent and small. Esti-
mates of MCP from allantoin in spot
urine samples followed NRC estimates.
Results demonstrate that allantoin is
an effective predictor of MCP flow.
Introduction
Purines are one of the building
blocks used in the synthesis of
DNA and RNA. Feed purines are
essentially totally degraded in the
rumen leaving only purines of
microbial origin for passage to the
duodenum. Therefore, purines have
commonly been used to estimate
microbial crude protein (MCP) flow
in studies assessing protein status
of beef cattle. However, this requires
duodenal fistulation resulting in
laborious experiments with few
cattle. Urinary allantoin is derived
from the breakdown of purines.
Recent research (2001 Nebraska
Beef Report, pp. 115-116) has
shown a strong linear relationship
Table 1. Composition of finishing diets (% of DM).
Dieta
Ingredient HMC BRAN SBM
High-moisture corn 88.3 68.3 60.5
Corn bran — 20.0 20.0
Soybean meal — — 7.8
Cottonseed hulls 6.7 6.7 6.7
Dry supplementb 5.0 5.0 5.0
Fine ground milo 1.68 1.67 2.98
Limestone 1.50 1.49 1.36
Urea 0.90 0.90 —
Potassium Chloride 0.43 0.45 0.17
Salt 0.30 0.30 0.30
Tallow 0.10 0.10 0.10
Trace mineral premix 0.05 0.05 0.05
Rumensin premix 0.02 0.02 0.02
Tylan premix 0.01 0.01 0.01
Vitamin premix 0.01 0.01 0.01
aHMC=high-moisture corn diet, BRAN=corn bran diet, SBM=soybean meal diet.
bAll diets supplemented to contain a minimum of 0.6% Ca, 0.24% P, 0.6% K, and 0.1% S
(DM basis). All diets contained 32 g/ton monensin and 11 g/ton tylosin (DM basis).
Page 29 — 2004 Nebraska Beef Report
collection day at 0800, 1100, 1400,
and 1700. The molar ratio of
allantoin to creatinine was calcu-
lated for each urine sample. We
assumed daily urinary creatinine
output was equal to 16.4 mg/lb
BW. To calculate daily allantoin
output (moles/day), the allantoin to
creatinine ratio was multiplied by
assumed daily creatinine output.
Estimated MCP flow was calcu-
lated from daily allantoin output
according to equations outlined
previously (2002 Nebraska Beef
Report, pp. 66-68). Estimates of
microbial efficiency (g/lb DM) were
calculated by dividing estimated
MCP supply by digestible DMI.
Data were analyzed as repeated
measures using the Mixed proce-
dure of SAS. For intake and ruminal
pH analyses, collection day repre-
sented repeated observations. For
urine data analyses, collection day
and time of collection were the
repeated observations. To deter-
mine the effect of corn bran addi-
tion, a contrast was used to
compare the HMC diet to both of
the corn bran containing diets. To
determine the effect of supplemen-
tal DIP source, a contrast was used
to compare the BRAN and SBM
diets. Additionally, linear and qua-
dratic effects of time and day were
tested with orthogonal contrasts.
The REG procedure of SAS was
used to compare MCP estimates
from urinary allantoin to estimates
from Level 1 of the NRC (1996)
model.
Results
Ruminal pH below 5.6 is gener-
ally used to define subacute acido-
sis. Results of the current trial
indicate the presence of subacute
acidosis. Heifers consuming the
HMC diet had an average ruminal
pH of 5.44 (Table 2). Additionally,
those heifers spent almost 15 hours
of each 24-hour collection below a
pH of 5.6 (Table 2). Intakes were
variable and treatment and collec-
tion day interacted (P<0.01) with
Table 2. Effect of HMC replacement with corn bran or supplemental degradable
protein source on digestion, ruminal pH, and microbial estimates.
Dieta Contrastsb
Item HMC BRAN SBM SEM 1 2
DMI, lb/day 22.2 25.1 23.8 1.5 0.14 0.35
Digestible DMI, lb/day 18.7 20.5 18.7 1.3 0.49 0.22
Ruminal pH 5.44 5.78 5.88 0.18 0.01 0.46
Time pH below 5.6, min 887 576 428 212 0.09 0.49
A:Cc 1.05 1.30 1.23 0.09 0.02 0.38
Urine volume, L/dayd 31.6 32.2 25.8 9.4 0.71 0.38
MCP, g/daye 740 966 913 88 0.02 0.47
Microbial efficiencyf 38.8 46.0 48.6 4.0 0.05 0.54
aHMC=high-moisture corn diet, BRAN=corn bran diet, SBM=soybean meal diet.
bContrast 1 is comparison of HMC to average of both corn bran containing diets;
Contrast 2 is comparison of BRAN and SBM.
cMolar ratio of allantoin to creatinine.
dUrine volume calculated from creatinine output.
eMicrobial crude protein.
fMicrobial efficiency calculated as g MCP/lb digestible DMI.
(Continued on next page)
intake once daily at 0900. Chromic
oxide was used as an indigestible
marker to calculate total-tract diges-
tion and was administered through
the ruminal cannula twice daily at
0800 and 1700. Feed intake and
ruminal pH were monitored con-
tinuously with feed weight and
ruminal pH recorded every minute
during the 5 day collection period.
Spot urine and fecal grab
samples were obtained on each
Figure 1. Daily variation in dry matter intake. SEM=1.5. Treatment x day (P<0.01).
Linear effect of day within HMC (P=0.19). Linear effect of day within
BRAN (P<0.01). Linear effect of day within SBM (P=0.13). Differences in
means on a particular sampling day are denoted by letters beneath points:
a Contrast comparing HMC to both corn bran containing diets (P<0.10) and
b Contrast comparing BRAN and SBM (P<0.10).
30
25
20
15
10
5
0
D
M
I, 
lb
/
d
ay
HMC
BRAN
SBM
Linear (HMC)
Linear (BRAN)
Linear (SBM)
1 2 3 4 5
Day of Collection Period
b a ab ab
2004 Nebraska Beef Report — Page 30
DMI increasing linearly (P<0.01) for
the BRAN diet (Figure 1). This may
be an indication that the adaptation
period was not long enough. The
significance of differences in DMI
for HMC compared to corn bran
containing diets increased toward
the end of the collection period
(day 3, P=0.09; day 4, P=0.08; day 5,
P=0.04).
Estimates of MCP flow and
microbial efficiency from allantoin
to creatinine ratios in spot urine
samples followed the pH and
intake responses for dietary addi-
tion of corn bran. Treatment effects
for estimates of MCP interacted
with collection day (P=0.02), and
MCP was lower on day 2 (P=0.02),
day 4 (P=0.01), and day 5 (P<0.01)
for HMC versus the average of the
corn bran containing diets (Figure
2). On average, corn bran addition
increased MCP estimates by 27%
(P=0.02; Table 2). The interaction
for MCP estimates is explained by
the interaction found for intake.
When intake variation was taken
into account by calculating micro-
bial efficiency, the interaction was
no longer present (P=0.28), and
there was no main effect of collec-
tion day. However, microbial effi-
ciency increased (P=0.05) by 22%
with corn bran addition (Table 2).
Because there were no differences
in digestible DMI (Table 2), the
lower MCP value for HMC is attrib-
utable to lower microbial efficiency
as a result of lower ruminal pH.
The present study also was de-
signed to evaluate supplementing
SBM versus urea based on the hy-
pothesis that providing microbes a
source of true protein and amino
acids would increase microbial effi-
ciency and flow. There was no
effect on DMI, digestible DMI, or
ruminal pH when SBM was sup-
plemented relative to urea (Table 2).
Evaluation of the treatment by col-
lection day interactions discussed
previously for intake (Figure 1)
showed that DMI was higher for
SBM relative to BRAN on day 1
(P=0.05) and lower on day 4
(P=0.05), and day 5 (P=0.03). Evalu-
Figure 2. Daily variation in microbial protein estimates. SEM=103. Treatment x day
(P=0.02). Linear effect of day within HMC (P=0.01). Linear effect of day
within BRAN (P<0.01). Linear effect of day within SBM (P=0.45).
Differences in means on a particular sampling day are denoted by letters
beneath points: a contrast comparing HMC to both corn bran containing
diets (P<0.10) and b contrast comparing BRAN and SBM (P<0.10).
1200
1000
800
600
400
200
0
M
C
P
, 
g/
d
ay
a    a     ab
HMC
BRAN
SBM
Linear (HMC)
Linear (BRAN)
Linear (SBM)
1 2 3 4 5
Day of collection period
Figure 3. Diurnal variation in microbial protein estimates. SEM=75. Treatment x
time (P=0.19). Main effect of time (P=0.10). Linear effect of time (P=0.06).
1200
1000
800
600
400
200
0
M
C
P
, 
g/
d
ay
0800 1100 1400 1700
Time of day
ation of the treatment by collection
day interaction for MCP estimates
(Figure 2) indicates that MCP was
higher (P=0.05) only on day 5 of the
collection period for BRAN com-
pared to SBM. Microbial efficiency
did not differ between SBM and
BRAN (Table 2) treatments. These
results are in conflict with some
previous reports that indicated
MCP flow and efficiency were
higher for SBM versus urea supple-
Page 31 — 2004 Nebraska Beef Report
mented diets. However, those trials
were conducted with DRC-based
finishing diets, and it seems plau-
sible that the higher DIP value for
HMC relative to DRC would pro-
vide microbes with more true pro-
tein and amino acids decreasing
the response to SBM as a supple-
mental DIP source. Additionally,
this trial compared SBM and urea
in corn bran containing diets where
risk of acidosis had been reduced.
Estimates of urine volume
(L/day) did not differ with treat-
ment and were comparable to esti-
mates found in other research trials.
The allantoin to creatinine ratio
was only different (P=0.02) when
comparing HMC to the corn bran
containing diets representing the
increased MCP flow. Some previous
studies have found allantoin to
creatinine ratios and estimates of
MCP display diurnal variability.
This variability is acceptable as
long as it is consistent and predict-
able. Our most important finding in
this regard is that there was no time
of day by collection day interaction
for estimates of MCP (P=0.22). We
did show some diurnal variability
with a MCP estimates increasing
linearly (P=0.06) from 0800 to 1700
(Figure 3). However, MCP estimates
only increased by 63 g or 7% from
the first sampling time to the last. In
addition, there was no treatment x
time of day interaction for MCP
estimates. Using an assumed
creatinine output of 16.4 mg/lb BW
resulted in MCP estimates that were
in agreement with estimates from
the NRC (1996) model (Figure 4).
In conclusion, we observed an
increase in MCP flow and efficiency
estimated from allantoin excretion
in spot urine samples when aver-
age ruminal pH was increased by
adding corn bran to HMC-based
finishing diets. Additionally, there
were no differences in ruminal pH,
intake, or digestibility between diets
containing corn bran that were
supplemented with urea or SBM
resulting in no differences in MCP
flow or efficiency. There was little
diurnal variation in MCP estimates,
and daily variation due to changes
in intake was removed when micro-
bial efficiency was calculated. Esti-
mates of MCP followed NRC (1996)
estimates, but creatinine outputs
may need to be adjusted on an indi-
vidual animal basis to more accu-
rately and precisely estimate MCP.
This trial was conducted in a
metabolism setting with a small
number of animals. However, the
goal of developing a spot sampling
technique is to be capable of sam-
pling large numbers of animals in a
more typical production setting.
Results of a companion finishing
trial are also reported in this publi-
cation (pp. 32). In that trial, 120
head of heifers were fed the same
diets and spot sampled across the
feeding period.
1R. Allen McDonald, graduate
student; Terry J. Klopfenstein, professor,
Lincoln; Galen E. Erickson, assistant
professor, Lincoln; Tim W. Loy, research
technician; Kimberly M. Whittet,
laboratory supervisor, Lincoln.
1600
1400
1200
1000
800
600
400
200
0
M
C
P
, 
g/
d
ay
y = 0.71x + 192.08
R2 = 0.59
Isopletha
Linear Regression
  0    200 400 600 800    1000  1200  1400 1600
MCP estimated from NRC, g/d
Figure 4. Relationship between allantoin and NRC estimates of microbial protein. a
Isopleth is the line where estimates are equal and r2 is equal to 1.
Intercept (SE=161; P=0.25). Slope (SE=0.16; P<0.01).


https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1201&context=animalscinbcr

Effects of Corn Bran and Degradable Protein Source on Microbial Protein Estimated From Spot Urine Samples in Heifers

Abstract

Similar works

Full text

Available Versions

DigitalCommons@University of Nebraska

UNL | Libraries