Two experiments, calves fed November to May (WINTER) and yearlings fed May to September (SUMMER), were conducted to evaluate the effects of feeding a high level of wet distillers grains plus soluble (WDGS) and wheat straw or a corn control diet (CON) on average daily gain (ADG), feed-to-gain (F:G), manure nitrogen (N), and N losses. In both experiments, the CON treatment had greater dry matter intake(DMI), ADG hot carcass weight (HCW), marbling and fat depth. There was greater N intake and N excretion for both the WINTER and SUMMER experiments on the WDGS. However, for the WINTER experiment there was no difference in the amount of N in the manure due to diet or pen cleaning frequency. In the SUMMER experiment, cleaning pens monthly almost doubled dry matter (DM), organic matter (OM), and N removed in manure. There was a tendency for the WDGS treatment to have greater N loss than the control treatment in the WINTER experiment and a significant increase in N losses for the WDGS treatment in the SUMMER experiment, despite the greater amount of manure N removed

Benton, Joshua R

Erickson, Galen

Griffin, William A

Klopfenstein, Terry, Klopfenstein

Luebbe, Matt K.

Rich, Amy R.

English

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
Nebraska Beef Cattle Reports Animal Science Department 
2011 
Effect of Pen Cleaning Frequency and Feeding Distillers Grains 
and Wheat Straw on Nutrient Mass Balance and Performance of 
Feedlot Steers 
Amy R. Rich 
University of Nebraska-Lincoln 
Galen Erickson 
University of Nebraska-Lincoln, gerickson4@unl.edu 
Terry Klopfenstein Klopfenstein 
Universitiy of Nebraska-Lincoln, tklopfenstein1@unl.edu 
Matt K. Luebbe 
University of Nebraska - Lincoln, mluebbe2@unl.edu 
Joshua R. Benton 
University of Nebraska-Lincoln, jbenton2@unl.edu 
See next page for additional authors 
Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr 
 Part of the Animal Sciences Commons 
Rich, Amy R.; Erickson, Galen; Klopfenstein, Terry Klopfenstein; Luebbe, Matt K.; Benton, Joshua R.; and 
Griffin, William A., "Effect of Pen Cleaning Frequency and Feeding Distillers Grains and Wheat Straw on 
Nutrient Mass Balance and Performance of Feedlot Steers" (2011). Nebraska Beef Cattle Reports. 623. 
https://digitalcommons.unl.edu/animalscinbcr/623 
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. 
Authors 
Amy R. Rich, Galen Erickson, Terry Klopfenstein Klopfenstein, Matt K. Luebbe, Joshua R. Benton, and 
William A. Griffin 
This article is available at DigitalCommons@University of Nebraska - Lincoln: https://digitalcommons.unl.edu/
animalscinbcr/623 
Page 84 — 2011 Nebraska Beef Cattle Report  © The Board of Regents of the University of Nebraska.  All rights reserved.
Effect of Pen Cleaning Frequency and Feeding Distillers 
Grains and Wheat Straw on Nutrient Mass Balance and 
Performance of Feedlot Steers
used to increase the C:N ratio on the 
pen surface through the manure. 
Corn bran was effective in reducing 
N losses (2000 Nebraska Beef Cattle 
Report, pp. 54-57), but cattle perfor-
mance suffered. When steep was add-
ed to the corn bran treatment (2004 
Nebraska Beef Cattle Report, pp. 61-63; 
2005 Nebraska Beef Cattle Report, pp. 
54-56), ADG and F:G improved while 
N losses were reduced. Feeding wet 
DGS increased the amount of OM and 
N in the manure (2008 Nebraska Beef 
Cattle Report, pp. 53-56) but not to the 
same extent as corn bran. Pen clean-
ing frequency reduces the amount of 
time manure is exposed to the envi-
ronment, therefore, reducing amount 
of N lost through volatilization. 
Cleaning pens approximately every 
28 days has been reported to increase 
the amount of DM, OM, and N in 
the manure as well as decrease the N 
loss compared to cleaning at the end 
of the feeding period (2004 Nebraska 
Beef Cattle Report, pp. 72-73). Effects 
of feeding either a high level of wet 
distillers grains plus solubles with 
added fiber from wheat straw or a 
corn-based diet and pen cleaning 
frequency on cattle performance and 
nutrient mass balance were evaluated 
in our study.
Procedure
Cattle Performance
Two experiments were conducted 
using 128 steers each, calves (686 +/- 
22 lb) fed for 173 days from November 
to May (WINTER) and yearlings (805 
+/- 11 lb) fed for 145 days from May to 
October (SUMMER) to evaluate the 
effect of feeding high levels of both 
distillers grains and wheat straw com-
pared to a corn-based diet. Steers were 
stratified by body weight (BW) and 
assigned randomly to 16 pens  
(8 steers/pen). The SUMMER and 
WINTER dietary treatments consisted 
of 1) 85% dry-rolled corn, 5% molas-
ses, 5% wheat straw, 5% supplement 
(CON), or 2) 70% WDGS and 25% 
wheat straw, 5% supplement (WDGS 
+ straw). For the 21-day adaptation 
period, alfalfa hay was replaced by 
dry-rolled corn in the CON treat-
ment . Wheat straw was kept constant 
through the adaptation period and 
WDGS replaced alfalfa hay. A supple-
ment contained Rumensin, Tylan, and 
Thiamine at 30 g/ton DM, 90, and 130 
mg/steer daily, respectively, in both 
experiments. 
Steer calves in the WINTER trial 
were implanted on day 1 with Syn-
ovex Choice (Fort Dodge Animal 
Health) followed by a re-implant on 
day 85 with Synovex Choice. Yearling 
steers on the SUMMER trial were 
implanted with Revalor-S (Intervet 
Schering-Plough Animal Health) on 
day 35 of the feeding period. Due to 
the goal of harvesting steers at similar 
BW, the WINTER CON treatment 
was slaughtered on day 173 and the 
WDGS + straw treatment was slaugh-
tered on day 229. For the SUMMER, 
the yearling steers were slaughtered 
on day 144 for the CON and day 159 
for the WDGS + straw of the feeding 
experiment. Steers were harvested at a 
commercial abattoir (Greater Omaha) 
and hot carcass weight and liver scores 
were recorded on day of slaughter. 
Fat thickness, lean matter area, and 
USDA called marbling score were 
collected after a 48-hour chill. Final 
BW, ADG, and G:F were calculated 
based on HCW adjusted to a common 
dressing percentage of 63%. Feed ef-
ficiency data were analyzed as G:F and 
reported as F:G. 
Nutrient Mass Balance
Runoff N was determined using 
12 open feedlot pens with reten-
tion ponds to collect runoff from 
Amy R. Rich
Galen E. Erickson
Terry J. Klopfenstein
Matt K. Luebbe
Josh R. Benton
Will A. Griffin1
Summary
Two experiments, calves fed Novem-
ber to May (WINTER) and yearlings 
fed May to September (SUMMER), 
were conducted to evaluate the effects 
of feeding a high level of wet distillers 
grains plus soluble (WDGS) and wheat 
straw or a corn control diet (CON) 
on average daily gain (ADG), feed-
to-gain (F:G), manure nitrogen (N), 
and N losses. In both experiments, the 
CON treatment had greater dry matter 
intake (DMI), ADG hot carcass weight 
(HCW), marbling and fat depth. There 
was greater N intake and N excretion 
for both the WINTER and SUMMER 
experiments on the WDGS. However, 
for the WINTER experiment there was 
no difference in the amount of N in the 
manure due to diet or pen cleaning fre-
quency. In the SUMMER experiment, 
cleaning pens monthly almost doubled 
dry matter (DM), organic matter (OM), 
and N removed in manure. There was 
a tendency for the WDGS treatment 
to have greater N loss than the control 
treatment in the WINTER experiment 
and a significant increase in N losses for 
the WDGS treatment in the SUMMER 
experiment, despite the greater amount 
of manure N removed.
 
Introduction
One method that reduces N losses 
from feedlots is the addition of car-
bon (C) to the pen surface to increase 
C:N. Research at UNL has used either 
direct or indirect methods to increase 
the C:N ratio. Corn milling byprod-
ucts are a common indirect method 
© The Board of Regents of the University of Nebraska.  All rights reserved. 2011 Nebraska Beef Cattle Report  — Page 85 
(Continued on next page)
Table 1. Growth performance and carcass characteristics for steers fed during the WINTER trial.
Dietary Treatments1 CON WDGS + straw SEM P-value2
WINTER3    
Performance    
 DMI, lb 22.6 18.5 0.3 <0.01
 ADG, lb 3.57 2.36 0.4 <0.01
 Feed: Gain 6.33 7.81 .002 <0.01
SUMMER4    
Performance    
 DMI, lb 23.6 21.1 0.3 <0.01
 ADG, lb 3.15 2.62 0.05 <0.01
 Feed: Gain 7.47 8.00 0.003 0.04
1Dietary treatments: CON = Control corn-based diet, WDGS + straw = 70% WDGS, 25% wheat straw.
2F-test statistic for dietary treatment.
3 CON – fed for 173 days, WDGS – fed for 229 days.
4 CON – fed for 144 days, WDGS – fed for 156 days.
Table 2. Effect of dietary treatment on nitrogen mass balance1 during WINTER2 trial.
Dietary treatment3 CON WDGS + straw SEM P-value4
N intake 76.3 123.1 1.1 <0.01
N retention5 12.1 11.9 0.3 0.25
N excretion6 64.2 111.4 1.1 <0.01
Manure N7 23.6 26.2 3.5 0.63
N Run-off — — — —
N Lost 40.4 85.1 4.2 <0.01
N loss%8 62.9 76.4 5.1 0.08
    
DM removed 4776 5257 672 0.62
OM removed 1114 1418 170 0.23
1N mass balance analyzed for equal days across treatments.
2Values are expressed as lb/steer over entire feeding period (WINTER – fed for 173 days, SUMMER – 
fed for 144 days).
3Dietary treatments: CON = Control corn-based diet, WDGS + straw= 70% WDGS, 25% wheat straw.
4F-test statistic for dietary treatment.
5Calculated using the NRC net protein and net energy equations.
6Calculated as N intake – N retention.
7Manure N with correction for soil N.
8Calculated as N loss divided by N excretion.
Table 3. Effect of pen cleaning frequency on nitrogen mass balance1 during WINTER2 trial.
Pen cleaning frequency3 End Monthly SEM P-value4
N intake 100 99 1.103 0.39
N retention5 12.13 11.90 0.27 0.91
N excretion6 88.42 87.10 1.13 0.41
Manure N7 21.83 28.00 3.5 0.24
N Run-off — — — —
N Lost 66.37 59.10 4.19 0.21
N loss%8 73.5 65.5 5.1 0.29
    
DM removed 3837 6194 670 0.03
OM removed 1005 1526 170 0.05
1N mass balance analyzed for equal days across treatments.
2Values are expressed as lb/steer over entire feeding period (WINTER – fed for 173 day, SUMMER – fed 
for 144 days).
3Pen cleaning frequency: end = cleaned at end of feeding period, monthly = cleaned every 28 days.
4F-test statistic for dietary treatment.
5Calculated using the NRC net protein and net energy equations.
6Calculated as N intake – N retention.
7Manure N with correction for soil N.
8Calculated as N lost divided by N excretion.
rainfall. When runoff did occur, it 
was collected in the retention ponds 
and they were drained, sampled, and 
quantified. Pens that were randomly 
assigned to the 28-day pen clean-
ing schedule were scraped and the 
manure was piled on a cement apron 
and sampled for nutrient analysis 
while being loaded. Pens that were 
assigned to the end-of-the-feeding-
period cleaning were subjected to 
this cleaning after the steers were 
removed for harvest. Manure was 
then weighed before it was hauled to 
the University of Nebraska compost 
yard, where treatments were kept 
separated. Manure samples were then 
freeze dried for nutrient analysis and 
oven dried for DM calculation. Ingre-
dients were sampled weekly, and feed 
refusals were analyzed to determine 
nutrient intake using a weighted com-
posite on a pen basis. Individual steer 
N retention was calculated using the 
NRC net energy and protein equations 
(NRC, 1996). Nutrient excretion was 
determined by subtracting nutrient 
retention from intake. Total N lost (lb/
steer) was calculated by subtracting 
manure N and runoff N from excreted 
N. Percentage of N loss was calculated 
as N lost divided by N excreted. 
Animal performance and nutrient 
balance data were analyzed using the 
MIXED procedures of SAS as a 2 X 2 
factorial design with the factors being 
dietary treatments and timing of pen 
cleaning.
Results
Cattle Performance
There was no interaction between 
dietary treatments or pen cleaning 
frequency (P > 0.24) for either 
SUMMER or WINTER trials; there-
fore, only main effects will be dis-
cussed. In the WINTER, cattle fed 
the WDGS + straw had lower DMI 
(18.5 lb/day versus 22.6 lb/day). Aver-
age daily gain was also lower in the 
WDGS + straw treatment (2.36 versus 
3.57 lb), which resulted in a greater 
F:G (P < 0.01) compared to the cattle 
consuming the CON treatment. 
Page 86 — 2011 Nebraska Beef Cattle Report  © The Board of Regents of the University of Nebraska.  All rights reserved.
Cattle fed during the SUMMER 
trial had similar performance results 
as the WINTER calf-feds. Intake was 
lower for the WDGS + straw treatment 
(P < 0.01) as well as ADG (P < 0.01), 
which resulted in a higher F:G (8.00 lb 
versus 7.47 lb (P = 0.04)). This lower 
performance (Table 1) for the WDGS 
+ straw treatment is most likely due to 
the high inclusion of wheat straw in the 
diet, which was added to help increase 
the amount of OM on the pen surface 
and prevent sulfur-related polio-
encephalomalacia (2009 Nebraska Beef 
Cattle Report, pp. 79-80). 
Nutrient Balance
There was no interaction between 
dietary treatments or pen cleaning 
frequency (P > 0.10) for either SUM-
MER or WINTER trials; therefore, 
only main effects will be discussed.
Steers fed during the WINTER 
had greater N intake and N excretion 
when consuming the WDGS + straw 
treatment (P <0.01, Table 2). How-
ever, manure N was similar for the 
CON and WDGS + straw treatments. 
Therefore, because WDGS + straw 
calves excreted more N with the same 
amount in manure as the CON calves, 
the calves consuming the WDGS + 
straw had greater N losses (P < 0.01). 
There was a tendency (P = 0.08) for 
the WDGS + straw steers to have 
a greater N loss (76.4% vs. 62.9%) 
when expressed as a percentage of N 
excreted. There was not enough pre-
cipitation during the WINTER trial 
to generate runoff. The dry matter 
and OM removed were similar across 
dietary treatments (P > 0.10). Amount 
of DM removed was greater for pens 
cleaned monthly compared to those 
cleaned at the end of the feeding pe-
riod (P = 0.03) (Table 3).
Steers on trial in the SUMMER 
consuming the WDGS + straw had 
greater (P<0.01) N intake and N 
excretion , due to excess CP with the 
WDGS + straw treatment compared 
to the CON treatment (24% versus 
12%, Table 4). Runoff N was not 
impacted (P = 0.28) by either dietary 
treatments or pen cleaning frequency; 
however, there was almost double the 
Table 4. Effect of dietary treatment on nitrogen mass balance1 during SUMMER2 trial.
Dietary treatment3 CON WDGS + straw SEM P-value4
N intake 63.8 115.1 1.1 <0.01
N retention5 8.8 8.4 0.1 0.02
N excretion6 55.0 106.7 1.1 <0.01
Manure N7 17.4 31.7 1.7 <0.01
N Runoff 1.9 2.3 0.63 0.64
N Lost 33.5 69.9 2.2 <0.01
N loss%8 60.9 65.5 2.5 <0.01
DM removed 7784 12287 947 <0.01
OM removed 1160 2317 98 <0.01
1N mass balance analyzed for equal days across treatments.
2Values are expressed as lb/steer over entire feeding period (WINTER – fed for 173 days, SUMMER – 
fed for 144 days).
3Dietary treatments: CON = Control corn-based diet, WDGS + straw= 70% WDGS, 25% wheat straw.
4F-test statistic for dietary treatment.
5Calculated using the NRC net protein and net energy equations.
6Calculated as N intake – N retention.
7Manure N with correction for soil N.
8Calculated as N loss divided by N excretion.
Table 5. Effect of pen cleaning frequency on nitrogen mass balance1 during SUMMER1.
Pen cleaning frequency2 End Monthly SEM P-value3
N intake 90 89 0.68 0.68
N retention4 8.56 8.60 0.79 0.91
N excretion5 81.21 80.50 0.13 0.79
Manure N6 16.82 32.26 1.70 <0.01
N Run-off 3.51 5.76 1.39 0.28
N Lost 60.92 42.47 2.21 <0.01
N lost%7 164.6 114.06 5.53 <0.01
DM removed 6090 13981 941 <0.01
OM removed 1252 2225 98 <0.01
1Values are expressed as lb/steer over entire feeding period (WINTER – fed for 173 days, SUMMER – 
fed for 144 days).
2Pen cleaning frequency: end = cleaned at end of feeding period, monthly = cleaned every 28 days.
3F-test statistic for dietary treatment.
4Calculated using the NRC net protein and net energy equations.
5Calculated as N intake – N retention.
6Manure N with correction for soil N.
7Calculated as N lost divided by N excretion.
amount of manure N, DM, and OM 
removed for the steers consuming the 
WDGS + straw compared to the CON  
(P < 0.01). Table 5 reports the pen 
cleaning frequency results. Monthly 
pen cleaning also almost doubled  
(P < 0.01) the amount of N, DM, 
and OM removed in the manure. 
Despite increases in manure N, N 
losses were greater (P < 0.01) for the 
WDGS + straw compared to the CON 
treatment. Cleaning pens monthly 
decreased (P < 0.01) N losses by 8.4 
lb or 50.5% compared to cleaning at 
the end of the feeding period. Runoff 
N did not constitute much of what 
was excreted, resulting in 3.5% of N 
excreted for the CON treatment and 
2.2% for the WDGS + straw. 
These data indicate feeding 70% 
WDGS with 25% wheat straw does 
decrease DMI, ADG, and F:G year 
around. Feeding WDGS at 70% diet 
DM increased N intake and N excretion 
due to the high concentration of CP in 
the byproduct. Cleaning feedlot pens 
monthly does increase total amount 
of manure removed, but there is also a 
greater amount of OM and N removed.
1Amy R. Rich, graduate student; Galen 
E. Erickson, professor; Terry J. Klopfenstein, 
professor; Matt K. Luebbe, research technician; 
Josh R. Benton, research technician; Will A. Griffin, 
research technician, University of Nebraska–
Lincoln Department of Animal Science.


Effect of Pen Cleaning Frequency and Feeding Distillers Grains and Wheat Straw on Nutrient Mass Balance and Performance of Feedlot Steers

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Nebraska Beef Cattle Reports Animal Science Department 2011 Effect of Pen Cleaning Frequency and Feeding Distillers Grains and Wheat Straw on Nutrient Mass Balance and Performance of Feedlot Steers Amy R. Rich University of Nebraska-Lincoln Galen Erickson University of Nebraska-Lincoln, gerickson4@unl.edu Terry Klopfenstein Klopfenstein Universitiy of Nebraska-Lincoln, tklopfenstein1@unl.edu Matt K. Luebbe University of Nebraska - Lincoln, mluebbe2@unl.edu Joshua R. Benton University of Nebraska-Lincoln, jbenton2@unl.edu See next page for additional authors Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr  Part of the Animal Sciences Commons Rich, Amy R.; Erickson, Galen; Klopfenstein, Terry Klopfenstein; Luebbe, Matt K.; Benton, Joshua R.; and Griffin, William A., "Effect of Pen Cleaning Frequency and Feeding Distillers Grains and Wheat Straw on Nutrient Mass Balance and Performance of Feedlot Steers" (2011). Nebraska Beef Cattle Reports. 623. https://digitalcommons.unl.edu/animalscinbcr/623 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. Authors Amy R. Rich, Galen Erickson, Terry Klopfenstein Klopfenstein, Matt K. Luebbe, Joshua R. Benton, and William A. Griffin This article is available at DigitalCommons@University of Nebraska - Lincoln: https://digitalcommons.unl.edu/animalscinbcr/623 Page 84 — 2011 Nebraska Beef Cattle Report  © The Board of Regents of the University of Nebraska.  All rights reserved.Effect of Pen Cleaning Frequency and Feeding Distillers Grains and Wheat Straw on Nutrient Mass Balance and Performance of Feedlot Steersused to increase the C:N ratio on the pen surface through the manure. Corn bran was effective in reducing N losses (2000 Nebraska Beef Cattle Report, pp. 54-57), but cattle perfor-mance suffered. When steep was add-ed to the corn bran treatment (2004 Nebraska Beef Cattle Report, pp. 61-63; 2005 Nebraska Beef Cattle Report, pp. 54-56), ADG and F:G improved while N losses were reduced. Feeding wet DGS increased the amount of OM and N in the manure (2008 Nebraska Beef Cattle Report, pp. 53-56) but not to the same extent as corn bran. Pen clean-ing frequency reduces the amount of time manure is exposed to the envi-ronment, therefore, reducing amount of N lost through volatilization. Cleaning pens approximately every 28 days has been reported to increase the amount of DM, OM, and N in the manure as well as decrease the N loss compared to cleaning at the end of the feeding period (2004 Nebraska Beef Cattle Report, pp. 72-73). Effects of feeding either a high level of wet distillers grains plus solubles with added fiber from wheat straw or a corn-based diet and pen cleaning frequency on cattle performance and nutrient mass balance were evaluated in our study.ProcedureCattle PerformanceTwo experiments were conducted using 128 steers each, calves (686 +/- 22 lb) fed for 173 days from November to May (WINTER) and yearlings (805 +/- 11 lb) fed for 145 days from May to October (SUMMER) to evaluate the effect of feeding high levels of both distillers grains and wheat straw com-pared to a corn-based diet. Steers were stratified by body weight (BW) and assigned randomly to 16 pens  (8 steers/pen). The SUMMER and WINTER dietary treatments consisted of 1) 85% dry-rolled corn, 5% molas-ses, 5% wheat straw, 5% supplement (CON), or 2) 70% WDGS and 25% wheat straw, 5% supplement (WDGS + straw). For the 21-day adaptation period, alfalfa hay was replaced by dry-rolled corn in the CON treat-ment . Wheat straw was kept constant through the adaptation period and WDGS replaced alfalfa hay. A supple-ment contained Rumensin, Tylan, and Thiamine at 30 g/ton DM, 90, and 130 mg/steer daily, respectively, in both experiments. Steer calves in the WINTER trial were implanted on day 1 with Syn-ovex Choice (Fort Dodge Animal Health) followed by a re-implant on day 85 with Synovex Choice. Yearling steers on the SUMMER trial were implanted with Revalor-S (Intervet Schering-Plough Animal Health) on day 35 of the feeding period. Due to the goal of harvesting steers at similar BW, the WINTER CON treatment was slaughtered on day 173 and the WDGS + straw treatment was slaugh-tered on day 229. For the SUMMER, the yearling steers were slaughtered on day 144 for the CON and day 159 for the WDGS + straw of the feeding experiment. Steers were harvested at a commercial abattoir (Greater Omaha) and hot carcass weight and liver scores were recorded on day of slaughter. Fat thickness, lean matter area, and USDA called marbling score were collected after a 48-hour chill. Final BW, ADG, and G:F were calculated based on HCW adjusted to a common dressing percentage of 63%. Feed ef-ficiency data were analyzed as G:F and reported as F:G. Nutrient Mass BalanceRunoff N was determined using 12 open feedlot pens with reten-tion ponds to collect runoff from Amy R. RichGalen E. EricksonTerry J. KlopfensteinMatt K. LuebbeJosh R. BentonWill A. Griffin1SummaryTwo experiments, calves fed Novem-ber to May (WINTER) and yearlings fed May to September (SUMMER), were conducted to evaluate the effects of feeding a high level of wet distillers grains plus soluble (WDGS) and wheat straw or a corn control diet (CON) on average daily gain (ADG), feed-to-gain (F:G), manure nitrogen (N), and N losses. In both experiments, the CON treatment had greater dry matter intake (DMI), ADG hot carcass weight (HCW), marbling and fat depth. There was greater N intake and N excretion for both the WINTER and SUMMER experiments on the WDGS. However, for the WINTER experiment there was no difference in the amount of N in the manure due to diet or pen cleaning fre-quency. In the SUMMER experiment, cleaning pens monthly almost doubled dry matter (DM), organic matter (OM), and N removed in manure. There was a tendency for the WDGS treatment to have greater N loss than the control treatment in the WINTER experiment and a significant increase in N losses for the WDGS treatment in the SUMMER experiment, despite the greater amount of manure N removed. IntroductionOne method that reduces N losses from feedlots is the addition of car-bon (C) to the pen surface to increase C:N. Research at UNL has used either direct or indirect methods to increase the C:N ratio. Corn milling byprod-ucts are a common indirect method © The Board of Regents of the University of Nebraska.  All rights reserved. 2011 Nebraska Beef Cattle Report  — Page 85 (Continued on next page)Table 1. Growth performance and carcass characteristics for steers fed during the WINTER trial.Dietary Treatments1 CON WDGS + straw SEM P-value2WINTER3    Performance     DMI, lb 22.6 18.5 0.3 <0.01 ADG, lb 3.57 2.36 0.4 <0.01 Feed: Gain 6.33 7.81 .002 <0.01SUMMER4    Performance     DMI, lb 23.6 21.1 0.3 <0.01 ADG, lb 3.15 2.62 0.05 <0.01 Feed: Gain 7.47 8.00 0.003 0.041Dietary treatments: CON = Control corn-based diet, WDGS + straw = 70% WDGS, 25% wheat straw.2F-test statistic for dietary treatment.3 CON – fed for 173 days, WDGS – fed for 229 days.4 CON – fed for 144 days, WDGS – fed for 156 days.Table 2. Effect of dietary treatment on nitrogen mass balance1 during WINTER2 trial.Dietary treatment3 CON WDGS + straw SEM P-value4N intake 76.3 123.1 1.1 <0.01N retention5 12.1 11.9 0.3 0.25N excretion6 64.2 111.4 1.1 <0.01Manure N7 23.6 26.2 3.5 0.63N Run-off — — — —N Lost 40.4 85.1 4.2 <0.01N loss%8 62.9 76.4 5.1 0.08    DM removed 4776 5257 672 0.62OM removed 1114 1418 170 0.231N mass balance analyzed for equal days across treatments.2Values are expressed as lb/steer over entire feeding period (WINTER – fed for 173 days, SUMMER – fed for 144 days).3Dietary treatments: CON = Control corn-based diet, WDGS + straw= 70% WDGS, 25% wheat straw.4F-test statistic for dietary treatment.5Calculated using the NRC net protein and net energy equations.6Calculated as N intake – N retention.7Manure N with correction for soil N.8Calculated as N loss divided by N excretion.Table 3. Effect of pen cleaning frequency on nitrogen mass balance1 during WINTER2 trial.Pen cleaning frequency3 End Monthly SEM P-value4N intake 100 99 1.103 0.39N retention5 12.13 11.90 0.27 0.91N excretion6 88.42 87.10 1.13 0.41Manure N7 21.83 28.00 3.5 0.24N Run-off — — — —N Lost 66.37 59.10 4.19 0.21N loss%8 73.5 65.5 5.1 0.29    DM removed 3837 6194 670 0.03OM removed 1005 1526 170 0.051N mass balance analyzed for equal days across treatments.2Values are expressed as lb/steer over entire feeding period (WINTER – fed for 173 day, SUMMER – fed for 144 days).3Pen cleaning frequency: end = cleaned at end of feeding period, monthly = cleaned every 28 days.4F-test statistic for dietary treatment.5Calculated using the NRC net protein and net energy equations.6Calculated as N intake – N retention.7Manure N with correction for soil N.8Calculated as N lost divided by N excretion.rainfall. When runoff did occur, it was collected in the retention ponds and they were drained, sampled, and quantified. Pens that were randomly assigned to the 28-day pen clean-ing schedule were scraped and the manure was piled on a cement apron and sampled for nutrient analysis while being loaded. Pens that were assigned to the end-of-the-feeding-period cleaning were subjected to this cleaning after the steers were removed for harvest. Manure was then weighed before it was hauled to the University of Nebraska compost yard, where treatments were kept separated. Manure samples were then freeze dried for nutrient analysis and oven dried for DM calculation. Ingre-dients were sampled weekly, and feed refusals were analyzed to determine nutrient intake using a weighted com-posite on a pen basis. Individual steer N retention was calculated using the NRC net energy and protein equations (NRC, 1996). Nutrient excretion was determined by subtracting nutrient retention from intake. Total N lost (lb/steer) was calculated by subtracting manure N and runoff N from excreted N. Percentage of N loss was calculated as N lost divided by N excreted. Animal performance and nutrient balance data were analyzed using the MIXED procedures of SAS as a 2 X 2 factorial design with the factors being dietary treatments and timing of pen cleaning.ResultsCattle PerformanceThere was no interaction between dietary treatments or pen cleaning frequency (P > 0.24) for either SUMMER or WINTER trials; there-fore, only main effects will be dis-cussed. In the WINTER, cattle fed the WDGS + straw had lower DMI (18.5 lb/day versus 22.6 lb/day). Aver-age daily gain was also lower in the WDGS + straw treatment (2.36 versus 3.57 lb), which resulted in a greater F:G (P < 0.01) compared to the cattle consuming the CON treatment. Page 86 — 2011 Nebraska Beef Cattle Report  © The Board of Regents of the University of Nebraska.  All rights reserved.Cattle fed during the SUMMER trial had similar performance results as the WINTER calf-feds. Intake was lower for the WDGS + straw treatment (P < 0.01) as well as ADG (P < 0.01), which resulted in a higher F:G (8.00 lb versus 7.47 lb (P = 0.04)). This lower performance (Table 1) for the WDGS + straw treatment is most likely due to the high inclusion of wheat straw in the diet, which was added to help increase the amount of OM on the pen surface and prevent sulfur-related polio-encephalomalacia (2009 Nebraska Beef Cattle Report, pp. 79-80). Nutrient BalanceThere was no interaction between dietary treatments or pen cleaning frequency (P > 0.10) for either SUM-MER or WINTER trials; therefore, only main effects will be discussed.Steers fed during the WINTER had greater N intake and N excretion when consuming the WDGS + straw treatment (P <0.01, Table 2). How-ever, manure N was similar for the CON and WDGS + straw treatments. Therefore, because WDGS + straw calves excreted more N with the same amount in manure as the CON calves, the calves consuming the WDGS + straw had greater N losses (P < 0.01). There was a tendency (P = 0.08) for the WDGS + straw steers to have a greater N loss (76.4% vs. 62.9%) when expressed as a percentage of N excreted. There was not enough pre-cipitation during the WINTER trial to generate runoff. The dry matter and OM removed were similar across dietary treatments (P > 0.10). Amount of DM removed was greater for pens cleaned monthly compared to those cleaned at the end of the feeding pe-riod (P = 0.03) (Table 3).Steers on trial in the SUMMER consuming the WDGS + straw had greater (P<0.01) N intake and N excretion , due to excess CP with the WDGS + straw treatment compared to the CON treatment (24% versus 12%, Table 4). Runoff N was not impacted (P = 0.28) by either dietary treatments or pen cleaning frequency; however, there was almost double the Table 4. Effect of dietary treatment on nitrogen mass balance1 during SUMMER2 trial.Dietary treatment3 CON WDGS + straw SEM P-value4N intake 63.8 115.1 1.1 <0.01N retention5 8.8 8.4 0.1 0.02N excretion6 55.0 106.7 1.1 <0.01Manure N7 17.4 31.7 1.7 <0.01N Runoff 1.9 2.3 0.63 0.64N Lost 33.5 69.9 2.2 <0.01N loss%8 60.9 65.5 2.5 <0.01DM removed 7784 12287 947 <0.01OM removed 1160 2317 98 <0.011N mass balance analyzed for equal days across treatments.2Values are expressed as lb/steer over entire feeding period (WINTER – fed for 173 days, SUMMER – fed for 144 days).3Dietary treatments: CON = Control corn-based diet, WDGS + straw= 70% WDGS, 25% wheat straw.4F-test statistic for dietary treatment.5Calculated using the NRC net protein and net energy equations.6Calculated as N intake – N retention.7Manure N with correction for soil N.8Calculated as N loss divided by N excretion.Table 5. Effect of pen cleaning frequency on nitrogen mass balance1 during SUMMER1.Pen cleaning frequency2 End Monthly SEM P-value3N intake 90 89 0.68 0.68N retention4 8.56 8.60 0.79 0.91N excretion5 81.21 80.50 0.13 0.79Manure N6 16.82 32.26 1.70 <0.01N Run-off 3.51 5.76 1.39 0.28N Lost 60.92 42.47 2.21 <0.01N lost%7 164.6 114.06 5.53 <0.01DM removed 6090 13981 941 <0.01OM removed 1252 2225 98 <0.011Values are expressed as lb/steer over entire feeding period (WINTER – fed for 173 days, SUMMER – fed for 144 days).2Pen cleaning frequency: end = cleaned at end of feeding period, monthly = cleaned every 28 days.3F-test statistic for dietary treatment.4Calculated using the NRC net protein and net energy equations.5Calculated as N intake – N retention.6Manure N with correction for soil N.7Calculated as N lost divided by N excretion.amount of manure N, DM, and OM removed for the steers consuming the WDGS + straw compared to the CON  (P < 0.01). Table 5 reports the pen cleaning frequency results. Monthly pen cleaning also almost doubled  (P < 0.01) the amount of N, DM, and OM removed in the manure. Despite increases in manure N, N losses were greater (P < 0.01) for the WDGS + straw compared to the CON treatment. Cleaning pens monthly decreased (P < 0.01) N losses by 8.4 lb or 50.5% compared to cleaning at the end of the feeding period. Runoff N did not constitute much of what was excreted, resulting in 3.5% of N excreted for the CON treatment and 2.2% for the WDGS + straw. These data indicate feeding 70% WDGS with 25% wheat straw does decrease DMI, ADG, and F:G year around. Feeding WDGS at 70% diet DM increased N intake and N excretion due to the high concentration of CP in the byproduct. Cleaning feedlot pens monthly does increase total amount of manure removed, but there is also a greater amount of OM and N removed.1Amy R. Rich, graduate student; Galen E. Erickson, professor; Terry J. Klopfenstein, professor; Matt K. Luebbe, research technician; Josh R. Benton, research technician; Will A. Griffin, research technician, University of Nebraska–Lincoln Department of Animal Science.

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Effect of Pen Cleaning Frequency and Feeding Distillers Grains and Wheat Straw on Nutrient Mass Balance and Performance of Feedlot Steers

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