Two experiments were conducted to evaluate the effect of dietary cation-anion difference (DCAD) at two levels (-16 and +20 mEq) on feedlot performance and nutrient mass balance in open feedlots. Decreasing DCAD did not negatively impact cattle performance or carcass characteristics. Feeding negative DCAD diets resulted in lower manure pH in both the winter and summer experiments. Final soil core pH was reduced only in the winter experiment. Percentage of N lost was not influenced by DCAD in either experiment. The decrease in manure pH is likely not enough to reduce the amount of N lost in open feedlot pens

Benton, Joshua R.

Erickson, Galen E.

Greenquist, Matthew A.

Klopfenstein, Terry J.

Luebbe, Matt K.

English

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
Nebraska Beef Cattle Reports Animal Science Department 
2009 
Effect of Dietary Cation-Anion Difference on Feedlot Performance, 
Nitrogen Mass Balance and Manure pH in Open Feedlot Pens 
Matt K. Luebbe 
University of Nebraska - Lincoln, mluebbe2@unl.edu 
Galen E. Erickson 
University of Nebraska-Lincoln, gerickson4@unl.edu 
Terry J. Klopfenstein 
University of Nebraska-Lincoln, tklopfenstein1@unl.edu 
Matthew A. Greenquist 
University of Nebraska-Lincoln, mgreenquist2@unl.edu 
Joshua R. Benton 
University of Nebraska-Lincoln, jbenton2@unl.edu 
Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr 
 Part of the Animal Sciences Commons 
Luebbe, Matt K.; Erickson, Galen E.; Klopfenstein, Terry J.; Greenquist, Matthew A.; and Benton, Joshua R., 
"Effect of Dietary Cation-Anion Difference on Feedlot Performance, Nitrogen Mass Balance and Manure 
pH in Open Feedlot Pens" (2009). Nebraska Beef Cattle Reports. 524. 
https://digitalcommons.unl.edu/animalscinbcr/524 
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. 
© The Board of Regents of the University of Nebraska.  All rights reserved. 2009 Nebraska Beef Report  — Page 91 
Effect of Dietary Cation-Anion Difference on Feedlot
Performance, Nitrogen Mass Balance and Manure pH 
in Open Feedlot Pens
Matthew K. Luebbe
Galen E. Erickson
Terry J. Klopfenstein
Matt A. Greenquist
Josh R. Benton1
Summary
Two experiments were conducted 
to evaluate the effect of dietary cation-
anion difference (DCAD) at two levels 
(-16 and +20 mEq) on feedlot perfor-
mance and nutrient mass balance in 
open feedlots. Decreasing DCAD did not 
negatively impact cattle performance or 
carcass characteristics. Feeding negative 
DCAD diets resulted in lower manure 
pH in both the winter and summer 
experiments. Final soil core pH was 
reduced only in the winter experiment. 
Percentage of N lost was not influenced 
by DCAD in either experiment. The 
decrease in manure pH is likely not 
enough to reduce the amount of N lost 
in open feedlot pens.
Introduction
Direct addition of acid to cattle 
slurry has reduced N losses during 
storage (Frost et al., 1990, Journal 
of Agricultural Science), and prior 
to spreading slurry (Stevens et al., 
1989, Journal of Agricultural Science). 
Reducing urine and fecal pH on the 
pen surface may reduce the amount 
of N lost from open feedlot pens. 
Urinary pH can be lowered using 
the dietary cation-anion difference 
(DCAD, defined as milliequivalents 
(mEq) of [(Na + K) – (Cl + S)] per 100 
g of feed DM). The majority (60-80%) 
of N excreted by feedlot cattle is in the 
urine as urea, which is converted into 
ammonium by the urease enzyme. 
Lowering urinary pH may reduce 
the amount of ammonia volatilized 
by shifting a greater proportion of N 
into the ammonium form. The objec-
tives of these studies were to evaluate 
effects of DCAD level on steer perfor-
mance, soil core and manure pH, and 
N mass balance.
Procedure
Cattle Performance
Two experiments were conducted 
using 96 steers each; calves (573 + 
48 lb BW) were fed 196 days from 
November to May (WINTER) and 
yearlings (760 + 56 lb BW) fed 145 
days from June to October (SUM-
MER) to evaluate DCAD level on N 
balance, manure pH and soil core pH 
in open feedlots. Steers were blocked 
by BW, stratified within block and 
assigned randomly to pen (eight 
steers/pen). Dietary treatments con-
sisted of negative (-16 mEq, NEG) 
and positive (+20 mEq, POS) DCAD 
levels. Basal diets for both experi-
ments consisted of high-moisture and 
dry-rolled corn fed at a 1:1 ratio, 
20% WDGS, 7.5% alfalfa hay and 
5% supplement (DM basis). Sodium 
bicarbonate (1.2% diet DM) replaced 
a portion of fine ground corn in the 
positive diet and calcium chloride 
(0.75% diet DM) replaced a portion 
of fine ground corn and limestone in 
the negative diet. Calcium, phospho-
rus, potassium and sulfur were held 
constant at 0.65%, 0.40%, 0.72% and 
0.33%, respectively, in all diets. Cattle 
were adapted to finishing diets over 
a 21-day period, with the corn blend 
replacing alfalfa hay. Rumensin, Tylan 
and thiamine premix were formu-
lated for 320, 90 and 130 mg/head/
day, respectively, in both experiments 
assuming a 22 lb dry matter intake 
(DMI) for WINTER and 24.5 lb DMI 
for SUMMER.
Steers in the WINTER experiment 
were implanted on day 1 and day 83 
with Synovex Choice (Fort Dodge 
Animal Health, Overland Park, Kan.). 
Steers in the SUMMER experiment 
were implanted once on day 48 with 
Revalor-S (Intervet Inc. Somer-
ville, N.J.). Steers were slaughtered 
on day 196 (WINTER) and day 145 
(SUMMER) at a commercial abat-
toir (Greater Omaha, Omaha, Neb.). 
Hot carcass weights (HCW) and 
liver scores were recorded on day of 
slaughter. Fat thickness and LM area 
were measured after a 48-hour chill, 
and USDA called marbling score was 
recorded. Final BW, average daily gain 
(ADG) and feed-to-gain ratio (F:G) 
were calculated based on hot carcass 
weights adjusted to a common dress-
ing percentage of 63%. 
Nutrient Balance
Nutrient mass balance experiments 
were conducted using 12 open feedlot 
pens with retention ponds to col-
lect runoff. When rainfall occurred, 
the runoff collected in the retention 
ponds was drained and quantified 
using an air bubble flow meter (ISCO, 
Lincoln, Neb.). Before placing cattle 
in pens, 16 soil core samples (6-in 
depth) were taken from each pen in 
both experiments . After cattle were 
removed from pens, scraped manure 
was piled on a cement apron and 
sampled (n = 30) for nutrient analy-
sis while being loaded. Manure was 
weighed before it was hauled to the 
University of Nebraska compost yard. 
Manure was freeze-dried for nutri-
ent analysis and oven-dried for DM 
removal calculation. After manure 
was removed in a manner identical to 
removal before the experiments, soil 
core samples were taken from each 
pen. Soil core samples and manure 
from pen cleaning were analyzed for 
pH using a 1:1 ratio of distilled water 
and as-is sample. Dietary treatments 
were fed in the same pens for both 
experiments.
(Continued on next page)
Page 92 — 2009 Nebraska Beef Report  © The Board of Regents of the University of Nebraska.  All rights reserved.
Ingredients were sampled weekly, 
and feed refusals were analyzed to 
determine nutrient intake using a 
weighted composite on a pen basis. 
Individual steer N retention was cal-
culated using the National Research 
Council net energy and protein equa-
tions (NRC, 1996). Nutrient excretion 
was determined by subtracting nutri-
ent retention from intake (ASABE, 
2005). Total N lost (lb/steer) was cal-
culated by subtracting manure N (cor-
rected for soil N content) and runoff 
N from excreted N. Percentage of N 
loss was calculated as N lost divided 
by N excreted. Animal performance 
data were analyzed as a randomized 
complete block design with pen as 
the experimental unit. The effects of 
treatment and block were included in 
the model. Nutrient balance data were 
analyzed as a completely randomized 
design with pen as the experimental 
unit. Stepwise multiple regression 
analyses were performed to determine 
the effect of manure pH, initial soil 
core pH and final soil core pH on the 
amount of N lost, percentage of N loss 
and amount of manure N removed.
Results
Feedlot Performance
Dry matter intake, ADG, final  
BW, and HCW were not different  
(P > 0.10) among treatments in either 
experiment (Tables 1 and 2). Feed 
efficiency was improved (P = 0.05) for 
cattle consuming NEG diets compared 
with POS in the WINTER (5.66 and 
6.14, respectively) and numerically 
improved (P = 0.11) in the SUMMER 
(6.06 and 6.32, respectively). Calcu-
lated USDA yield grade and LM area 
tended (P = 0.10 and P = 0.08, respec-
tively) to be greater for cattle consum-
ing NEG diets than those consuming 
POS diets in the WINTER. Marbling 
score was greater (P = 0.04) for the 
NEG treatment compared with POS in 
the SUMMER experiment. Liver scores 
and 12th rib fat depth were not influ-
enced (P > 0.10) by DCAD in either 
experiment . In both experiments, 
cattle performance was not reduced 
due to negative DCAD diets; feed con-
versions improved in the WINTER 
and numerically improved in the 
SUMMER .
Nutrient Balance
Nitrogen intake, retention and 
excretion were similar (P > 0.10) 
among treatments for both experi-
ments (Tables 3 and 4). Amounts of 
DM, OM and N removed during pen 
cleaning also were similar (P > 0.50) 
among treatments in both experi-
ments. Amount of N lost was similar 
(P = 0.59) among treatments in the 
WINTER (28.4 and 30.8 lb for  
NEG and POS, respectively). Amount 
of N lost in the SUMMER tended  
(P = 0.07) to be greater for POS 
compared with NEG (47.3 and 
43.0 lb, respectively) . The differ-
ence in amount of N lost during the 
SUMMER may be due in part to a 
numerically greater amount of N 
intake and excretion for cattle fed the 
POS diet. Runoff N was not different  
Table 1. Growth performance and carcass characteristics for steers fed during WINTER.
Dietary Treatment1: NEG POS SEM P-value
Performance
 Initial BW, lb 574 574 18 0.96
 Final BW, lb2 1248 1234 24 0.56
 DMI, lb/d 19.3 20.1 0.5 0.12
 ADG, lb 3.44 3.37 0.11 0.48
 Feed: gain3 5.66 6.14 0.17 0.05
Carcass characteristics
 Hot carcass weight, lb 787 777 15 0.55
 Marbling score4 586 586 18 0.99
 LM, area in2. 12.9 12.4 0.3 0.08
 12th rib fat, in. 0.59 0.62 0.04 0.39
 Yield grade5 3.4 3.6 0.1 0.10
 Liver abscess, % 7.2 6.3 6.1 0.89
1Dietary treatments: NEG = negative dietary cation-anion difference (-16 mEq); POS = positive dietary 
cation-anion difference (+20 mEq).
2Calculated from hot carcass weight, adjusted to a common dressing percentage of 63.
3Analyzed as gain:feed, reciprocal of feed conversion.
4Marbling score: 400 = Slight0; 450 = Slight50; 500 = Small0, etc..
5Where yield grade = 2.5 + 2.5(fat thickness, in) – 0.32(LM area, in2) + 0.2(KPH fat, %) + 0.0038(hot 
carcass weight, lb).
Table 2. Growth performance and carcass characteristics for steers fed during SUMMER.
Dietary Treatment1: NEG POS SEM P-value
Performance
 Initial BW, lb 758 761 6 0.61
 Final BW, lb2 1345 1345 15 0.99
 DMI, lb/d 24.3 25.2 0.5 0.14
 ADG, lb 4.05 4.03 0.09 0.82
 Feed: gain3 6.06 6.32 0.14 0.11
Carcass characteristics
 Hot carcass weight, lb 847 847 9 0.99
 Marbling score4 523 543 8 0.04
 LM, area in2. 12.5 12.5 0.3 0.99
 12th rib fat, in. 0.59 0.57 0.03 0.59
 Yield grade5 3.7 3.7 0.2 0.73
 Liver abscess, % 8.5 15.0 5.7 0.29
1Dietary treatments: NEG = negative dietary cation-anion difference (-16 mEq); POS = positive dietary 
cation-anion difference (+20 mEq).
2Calculated from hot carcass weight, adjusted to a common dressing percentage of 63.
3Analyzed as gain:feed, reciprocal of feed conversion.
4Marbling score: 400 = Slight0; 450 = Slight50; 500 = Small0, etc..
5Where yield grade = 2.5 + 2.5(fat thickness, in) – 0.32(LM area, in2) + 0.2(KPH fat, %) + 0.0038(hot 
carcass weight, lb).
© The Board of Regents of the University of Nebraska.  All rights reserved. 2009 Nebraska Beef Report  — Page 93 
(P > 0.10) among treatments in both 
experiments and constituted 1.7% of 
excreted N in the WINTER and 2.2% 
of excreted N in the SUMMER. Per-
centage of N lost (N lost divided by 
N excreted) did not differ (P > 0.25) 
among treatments in both experi-
ments. Percent N lost was 39.1% and 
40.8% in the WINTER, and 61.3% 
and 64.6% in the SUMMER (for NEG 
and POS treatments, respectively).
Initial soil core pH for pens was 
greater in the WINTER (P = 0.04) for 
cattle receiving the NEG treatment 
than those receiving the POS treat-
ment (8.52 and 8.39, respectively). 
However, final soil core pH in the 
WINTER was greater in pens with 
cattle receiving the POS treatment 
compared with NEG (8.70 and 8.52, 
respectively). Manure pH in the 
WINTER experiment was greater  
(P < 0.01) for the POS treatment 
compared with NEG (8.80 and 8.40, 
respectively ). Initial soil core pH in 
the SUMMER was greater (P = 0.04) 
for POS compared with NEG, but 
final soil core pH did not differ  
(P = 0.29) among treatment (8.01 and 
8.07 for NEG and POS, respectively). 
Manure pH in the SUMMER experi-
ment was greater (P < 0.01) for POS 
compared with NEG (8.12 and 7.70, 
respectively). Differences observed for 
manure pH and final soil core pH did 
not correspond with N mass balance. 
In the WINTER experiment, manure 
pH, initial soil core pH and final soil 
core pH did not explain a significant 
amount of variability (P > 0.15) for 
manure N, N lost or percent N loss. In 
the SUMMER experiment, initial soil 
core pH explained 40% (P = 0.03) of 
the variation for the amount of N lost, 
and 31% (P = 0.06) of the variation for 
percent N loss. Our hypothesis was 
that N excreted in the urine would 
mix primarily with manure in areas 
of the pen (along the bunk pad and 
water tank) where cattle excrete feces, 
resulting in manure pH being a better 
indicator of N loss.
Table 3. Effect of dietary treatment on soil core pH, manure pH and nitrogen mass balance during 
WINTER.1
Dietary Treatment2: NEG POS SEM P-value
N intake 86.8 89.8 2.2 0.21
N retention3 14.2 14.4 0.5 0.74
N excretion4 72.7 75.4 2.0 0.21
Manure N 41.4 39.1 6.5 0.73
N run-off 1.09 1.42 0.23 0.18
N lost 28.4 30.8 4.5 0.59
N loss, %5 39.1 40.8 5.9 0.78
DM removed 4262 4122 806 0.87
OM removed 495 515 72 0.78
Initial core pH 8.52 8.39 0.06 0.04
Final core pH 8.52 8.70 0.05 <0.01
Manure pH 8.40 8.80 0.06 <0.01
1Values are expressed as lb/steer over entire feeding period (196 DOF) unless noted.
2Dietary treatments: NEG = negative dietary cation-anion difference (-16 mEq); POS = positive dietary 
cation-anion difference (+20 mEq).
3Calculated using the NRC net protein and net energy equations.
4Calculated as N intake – N retention.
5Calculated as N lost divided by N excreted.
Table 4. Effect of dietary treatment on soil core pH, manure pH, and nitrogen mass balance during 
SUMMER.1
Dietary Treatment2: NEG POS SEM P-value
N intake 81.9 84.6 1.8 0.16
N retention3 11.5 11.4 0.28 0.56
N excretion4 70.3 73.3 1.7 0.11
Manure N 25.9 24.4 3.3 0.67
N run-off 1.51 1.64 0.39 0.76
N lost 43.0 47.3 2.11 0.07
N loss, %5 61.3 64.6 3.7 0.39
DM removed 2399 2599 383 0.61
OM removed 383 380 42 0.93
Initial core pH 8.52 8.70 0.08 0.04
Final core pH 8.01 8.07 0.06 0.29
Manure pH 7.70 8.12 0.07 <0.01
1Values are expressed as lb/steer over entire feeding period (196 DOF) unless noted.
2Dietary treatments: NEG = negative dietary cation-anion difference (-16 mEq); POS = positive dietary 
cation-anion difference (+20 mEq).
3Calculated using the NRC net protein and net energy equations.
4Calculated as N intake – N retention.
5Calculated as N lost divided by N excreted.
These data suggest that feedlot per-
formance and carcass characteristics 
are similar for cattle fed with negative 
and positive DCAD levels in diets 
with WDGS. The decrease in soil core 
and manure pH is likely not enough 
to decrease N losses in open feedlot 
pens. Calcium carbonate in the feces 
and the buffering capacity of soil in 
feedlot pens appears be great enough 
to offset the lower urinary pH of cattle 
fed negative DCAD diets.
1Matthew K. Luebbe, research technician; 
Galen E. Erickson, associate professor; Terry 
J. Klopfenstein, professor; Matt A. Greenquist, 
research technician; Josh R. Benton, research 
technician, Animal Science , Lincoln, Neb.


Effect of Dietary Cation-Anion Difference on Feedlot Performance, Nitrogen Mass Balance and Manure pH in Open Feedlot Pens

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Nebraska Beef Cattle Reports Animal Science Department 2009 Effect of Dietary Cation-Anion Difference on Feedlot Performance, Nitrogen Mass Balance and Manure pH in Open Feedlot Pens Matt K. Luebbe University of Nebraska - Lincoln, mluebbe2@unl.edu Galen E. Erickson University of Nebraska-Lincoln, gerickson4@unl.edu Terry J. Klopfenstein University of Nebraska-Lincoln, tklopfenstein1@unl.edu Matthew A. Greenquist University of Nebraska-Lincoln, mgreenquist2@unl.edu Joshua R. Benton University of Nebraska-Lincoln, jbenton2@unl.edu Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr  Part of the Animal Sciences Commons Luebbe, Matt K.; Erickson, Galen E.; Klopfenstein, Terry J.; Greenquist, Matthew A.; and Benton, Joshua R., "Effect of Dietary Cation-Anion Difference on Feedlot Performance, Nitrogen Mass Balance and Manure pH in Open Feedlot Pens" (2009). Nebraska Beef Cattle Reports. 524. https://digitalcommons.unl.edu/animalscinbcr/524 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. © The Board of Regents of the University of Nebraska.  All rights reserved. 2009 Nebraska Beef Report  — Page 91 Effect of Dietary Cation-Anion Difference on FeedlotPerformance, Nitrogen Mass Balance and Manure pH in Open Feedlot PensMatthew K. LuebbeGalen E. EricksonTerry J. KlopfensteinMatt A. GreenquistJosh R. Benton1SummaryTwo experiments were conducted to evaluate the effect of dietary cation-anion difference (DCAD) at two levels (-16 and +20 mEq) on feedlot perfor-mance and nutrient mass balance in open feedlots. Decreasing DCAD did not negatively impact cattle performance or carcass characteristics. Feeding negative DCAD diets resulted in lower manure pH in both the winter and summer experiments. Final soil core pH was reduced only in the winter experiment. Percentage of N lost was not influenced by DCAD in either experiment. The decrease in manure pH is likely not enough to reduce the amount of N lost in open feedlot pens.IntroductionDirect addition of acid to cattle slurry has reduced N losses during storage (Frost et al., 1990, Journal of Agricultural Science), and prior to spreading slurry (Stevens et al., 1989, Journal of Agricultural Science). Reducing urine and fecal pH on the pen surface may reduce the amount of N lost from open feedlot pens. Urinary pH can be lowered using the dietary cation-anion difference (DCAD, defined as milliequivalents (mEq) of [(Na + K) – (Cl + S)] per 100 g of feed DM). The majority (60-80%) of N excreted by feedlot cattle is in the urine as urea, which is converted into ammonium by the urease enzyme. Lowering urinary pH may reduce the amount of ammonia volatilized by shifting a greater proportion of N into the ammonium form. The objec-tives of these studies were to evaluate effects of DCAD level on steer perfor-mance, soil core and manure pH, and N mass balance.ProcedureCattle PerformanceTwo experiments were conducted using 96 steers each; calves (573 + 48 lb BW) were fed 196 days from November to May (WINTER) and yearlings (760 + 56 lb BW) fed 145 days from June to October (SUM-MER) to evaluate DCAD level on N balance, manure pH and soil core pH in open feedlots. Steers were blocked by BW, stratified within block and assigned randomly to pen (eight steers/pen). Dietary treatments con-sisted of negative (-16 mEq, NEG) and positive (+20 mEq, POS) DCAD levels. Basal diets for both experi-ments consisted of high-moisture and dry-rolled corn fed at a 1:1 ratio, 20% WDGS, 7.5% alfalfa hay and 5% supplement (DM basis). Sodium bicarbonate (1.2% diet DM) replaced a portion of fine ground corn in the positive diet and calcium chloride (0.75% diet DM) replaced a portion of fine ground corn and limestone in the negative diet. Calcium, phospho-rus, potassium and sulfur were held constant at 0.65%, 0.40%, 0.72% and 0.33%, respectively, in all diets. Cattle were adapted to finishing diets over a 21-day period, with the corn blend replacing alfalfa hay. Rumensin, Tylan and thiamine premix were formu-lated for 320, 90 and 130 mg/head/day, respectively, in both experiments assuming a 22 lb dry matter intake (DMI) for WINTER and 24.5 lb DMI for SUMMER.Steers in the WINTER experiment were implanted on day 1 and day 83 with Synovex Choice (Fort Dodge Animal Health, Overland Park, Kan.). Steers in the SUMMER experiment were implanted once on day 48 with Revalor-S (Intervet Inc. Somer-ville, N.J.). Steers were slaughtered on day 196 (WINTER) and day 145 (SUMMER) at a commercial abat-toir (Greater Omaha, Omaha, Neb.). Hot carcass weights (HCW) and liver scores were recorded on day of slaughter. Fat thickness and LM area were measured after a 48-hour chill, and USDA called marbling score was recorded. Final BW, average daily gain (ADG) and feed-to-gain ratio (F:G) were calculated based on hot carcass weights adjusted to a common dress-ing percentage of 63%. Nutrient BalanceNutrient mass balance experiments were conducted using 12 open feedlot pens with retention ponds to col-lect runoff. When rainfall occurred, the runoff collected in the retention ponds was drained and quantified using an air bubble flow meter (ISCO, Lincoln, Neb.). Before placing cattle in pens, 16 soil core samples (6-in depth) were taken from each pen in both experiments . After cattle were removed from pens, scraped manure was piled on a cement apron and sampled (n = 30) for nutrient analy-sis while being loaded. Manure was weighed before it was hauled to the University of Nebraska compost yard. Manure was freeze-dried for nutri-ent analysis and oven-dried for DM removal calculation. After manure was removed in a manner identical to removal before the experiments, soil core samples were taken from each pen. Soil core samples and manure from pen cleaning were analyzed for pH using a 1:1 ratio of distilled water and as-is sample. Dietary treatments were fed in the same pens for both experiments.(Continued on next page)Page 92 — 2009 Nebraska Beef Report  © The Board of Regents of the University of Nebraska.  All rights reserved.Ingredients were sampled weekly, and feed refusals were analyzed to determine nutrient intake using a weighted composite on a pen basis. Individual steer N retention was cal-culated using the National Research Council net energy and protein equa-tions (NRC, 1996). Nutrient excretion was determined by subtracting nutri-ent retention from intake (ASABE, 2005). Total N lost (lb/steer) was cal-culated by subtracting manure N (cor-rected for soil N content) and runoff N from excreted N. Percentage of N loss was calculated as N lost divided by N excreted. Animal performance data were analyzed as a randomized complete block design with pen as the experimental unit. The effects of treatment and block were included in the model. Nutrient balance data were analyzed as a completely randomized design with pen as the experimental unit. Stepwise multiple regression analyses were performed to determine the effect of manure pH, initial soil core pH and final soil core pH on the amount of N lost, percentage of N loss and amount of manure N removed.ResultsFeedlot PerformanceDry matter intake, ADG, final  BW, and HCW were not different  (P > 0.10) among treatments in either experiment (Tables 1 and 2). Feed efficiency was improved (P = 0.05) for cattle consuming NEG diets compared with POS in the WINTER (5.66 and 6.14, respectively) and numerically improved (P = 0.11) in the SUMMER (6.06 and 6.32, respectively). Calcu-lated USDA yield grade and LM area tended (P = 0.10 and P = 0.08, respec-tively) to be greater for cattle consum-ing NEG diets than those consuming POS diets in the WINTER. Marbling score was greater (P = 0.04) for the NEG treatment compared with POS in the SUMMER experiment. Liver scores and 12th rib fat depth were not influ-enced (P > 0.10) by DCAD in either experiment . In both experiments, cattle performance was not reduced due to negative DCAD diets; feed con-versions improved in the WINTER and numerically improved in the SUMMER .Nutrient BalanceNitrogen intake, retention and excretion were similar (P > 0.10) among treatments for both experi-ments (Tables 3 and 4). Amounts of DM, OM and N removed during pen cleaning also were similar (P > 0.50) among treatments in both experi-ments. Amount of N lost was similar (P = 0.59) among treatments in the WINTER (28.4 and 30.8 lb for  NEG and POS, respectively). Amount of N lost in the SUMMER tended  (P = 0.07) to be greater for POS compared with NEG (47.3 and 43.0 lb, respectively) . The differ-ence in amount of N lost during the SUMMER may be due in part to a numerically greater amount of N intake and excretion for cattle fed the POS diet. Runoff N was not different  Table 1. Growth performance and carcass characteristics for steers fed during WINTER.Dietary Treatment1: NEG POS SEM P-valuePerformance Initial BW, lb 574 574 18 0.96 Final BW, lb2 1248 1234 24 0.56 DMI, lb/d 19.3 20.1 0.5 0.12 ADG, lb 3.44 3.37 0.11 0.48 Feed: gain3 5.66 6.14 0.17 0.05Carcass characteristics Hot carcass weight, lb 787 777 15 0.55 Marbling score4 586 586 18 0.99 LM, area in2. 12.9 12.4 0.3 0.08 12th rib fat, in. 0.59 0.62 0.04 0.39 Yield grade5 3.4 3.6 0.1 0.10 Liver abscess, % 7.2 6.3 6.1 0.891Dietary treatments: NEG = negative dietary cation-anion difference (-16 mEq); POS = positive dietary cation-anion difference (+20 mEq).2Calculated from hot carcass weight, adjusted to a common dressing percentage of 63.3Analyzed as gain:feed, reciprocal of feed conversion.4Marbling score: 400 = Slight0; 450 = Slight50; 500 = Small0, etc..5Where yield grade = 2.5 + 2.5(fat thickness, in) – 0.32(LM area, in2) + 0.2(KPH fat, %) + 0.0038(hot carcass weight, lb).Table 2. Growth performance and carcass characteristics for steers fed during SUMMER.Dietary Treatment1: NEG POS SEM P-valuePerformance Initial BW, lb 758 761 6 0.61 Final BW, lb2 1345 1345 15 0.99 DMI, lb/d 24.3 25.2 0.5 0.14 ADG, lb 4.05 4.03 0.09 0.82 Feed: gain3 6.06 6.32 0.14 0.11Carcass characteristics Hot carcass weight, lb 847 847 9 0.99 Marbling score4 523 543 8 0.04 LM, area in2. 12.5 12.5 0.3 0.99 12th rib fat, in. 0.59 0.57 0.03 0.59 Yield grade5 3.7 3.7 0.2 0.73 Liver abscess, % 8.5 15.0 5.7 0.291Dietary treatments: NEG = negative dietary cation-anion difference (-16 mEq); POS = positive dietary cation-anion difference (+20 mEq).2Calculated from hot carcass weight, adjusted to a common dressing percentage of 63.3Analyzed as gain:feed, reciprocal of feed conversion.4Marbling score: 400 = Slight0; 450 = Slight50; 500 = Small0, etc..5Where yield grade = 2.5 + 2.5(fat thickness, in) – 0.32(LM area, in2) + 0.2(KPH fat, %) + 0.0038(hot carcass weight, lb).© The Board of Regents of the University of Nebraska.  All rights reserved. 2009 Nebraska Beef Report  — Page 93 (P > 0.10) among treatments in both experiments and constituted 1.7% of excreted N in the WINTER and 2.2% of excreted N in the SUMMER. Per-centage of N lost (N lost divided by N excreted) did not differ (P > 0.25) among treatments in both experi-ments. Percent N lost was 39.1% and 40.8% in the WINTER, and 61.3% and 64.6% in the SUMMER (for NEG and POS treatments, respectively).Initial soil core pH for pens was greater in the WINTER (P = 0.04) for cattle receiving the NEG treatment than those receiving the POS treat-ment (8.52 and 8.39, respectively). However, final soil core pH in the WINTER was greater in pens with cattle receiving the POS treatment compared with NEG (8.70 and 8.52, respectively). Manure pH in the WINTER experiment was greater  (P < 0.01) for the POS treatment compared with NEG (8.80 and 8.40, respectively ). Initial soil core pH in the SUMMER was greater (P = 0.04) for POS compared with NEG, but final soil core pH did not differ  (P = 0.29) among treatment (8.01 and 8.07 for NEG and POS, respectively). Manure pH in the SUMMER experi-ment was greater (P < 0.01) for POS compared with NEG (8.12 and 7.70, respectively). Differences observed for manure pH and final soil core pH did not correspond with N mass balance. In the WINTER experiment, manure pH, initial soil core pH and final soil core pH did not explain a significant amount of variability (P > 0.15) for manure N, N lost or percent N loss. In the SUMMER experiment, initial soil core pH explained 40% (P = 0.03) of the variation for the amount of N lost, and 31% (P = 0.06) of the variation for percent N loss. Our hypothesis was that N excreted in the urine would mix primarily with manure in areas of the pen (along the bunk pad and water tank) where cattle excrete feces, resulting in manure pH being a better indicator of N loss.Table 3. Effect of dietary treatment on soil core pH, manure pH and nitrogen mass balance during WINTER.1Dietary Treatment2: NEG POS SEM P-valueN intake 86.8 89.8 2.2 0.21N retention3 14.2 14.4 0.5 0.74N excretion4 72.7 75.4 2.0 0.21Manure N 41.4 39.1 6.5 0.73N run-off 1.09 1.42 0.23 0.18N lost 28.4 30.8 4.5 0.59N loss, %5 39.1 40.8 5.9 0.78DM removed 4262 4122 806 0.87OM removed 495 515 72 0.78Initial core pH 8.52 8.39 0.06 0.04Final core pH 8.52 8.70 0.05 <0.01Manure pH 8.40 8.80 0.06 <0.011Values are expressed as lb/steer over entire feeding period (196 DOF) unless noted.2Dietary treatments: NEG = negative dietary cation-anion difference (-16 mEq); POS = positive dietary cation-anion difference (+20 mEq).3Calculated using the NRC net protein and net energy equations.4Calculated as N intake – N retention.5Calculated as N lost divided by N excreted.Table 4. Effect of dietary treatment on soil core pH, manure pH, and nitrogen mass balance during SUMMER.1Dietary Treatment2: NEG POS SEM P-valueN intake 81.9 84.6 1.8 0.16N retention3 11.5 11.4 0.28 0.56N excretion4 70.3 73.3 1.7 0.11Manure N 25.9 24.4 3.3 0.67N run-off 1.51 1.64 0.39 0.76N lost 43.0 47.3 2.11 0.07N loss, %5 61.3 64.6 3.7 0.39DM removed 2399 2599 383 0.61OM removed 383 380 42 0.93Initial core pH 8.52 8.70 0.08 0.04Final core pH 8.01 8.07 0.06 0.29Manure pH 7.70 8.12 0.07 <0.011Values are expressed as lb/steer over entire feeding period (196 DOF) unless noted.2Dietary treatments: NEG = negative dietary cation-anion difference (-16 mEq); POS = positive dietary cation-anion difference (+20 mEq).3Calculated using the NRC net protein and net energy equations.4Calculated as N intake – N retention.5Calculated as N lost divided by N excreted.These data suggest that feedlot per-formance and carcass characteristics are similar for cattle fed with negative and positive DCAD levels in diets with WDGS. The decrease in soil core and manure pH is likely not enough to decrease N losses in open feedlot pens. Calcium carbonate in the feces and the buffering capacity of soil in feedlot pens appears be great enough to offset the lower urinary pH of cattle fed negative DCAD diets.1Matthew K. Luebbe, research technician; Galen E. Erickson, associate professor; Terry J. Klopfenstein, professor; Matt A. Greenquist, research technician; Josh R. Benton, research technician, Animal Science , Lincoln, Neb.

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Effect of Dietary Cation-Anion Difference on Feedlot Performance, Nitrogen Mass Balance and Manure pH in Open Feedlot Pens

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