Six ruminally cannulated steers were used in a 6 x 6 Latin square with treatments arranged as a 2 x 3 factorial with alfalfa hay or cornstalks included at a normal, low or zero level on an equal neutral detergent fiber (NDF) basis. The base finishing diet contained 30% wet distillers grains plus solubles (WDGS). No source x level interactions were observed. Roughage source had no effect on nutrient intake, dry matter (DM) and organic matter (OM) digestibility or ruminal pH. Digestibility of NDF tended to be higher for alfalfa hay compared to cornstalks. Ruminal pH, DMI and NDF intake increased linearly while nutrient digestibility decreased linearly as roughage level increased. These data indicate that in finishing diets containing 30% wet distillers grains plus solubles (WDGS) roughages can be exchanged on an equal NDF basis and it is not beneficial to completely eliminate roughage sources from the diet

Benton, Josh R.

Buckner, Crystal D.

Erickson, Galen E.

Klopfenstein, Terry J.

Meyer, Nathan F.

English

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
Nebraska Beef Cattle Reports Animal Science Department 
2009 
Effects of Roughage Source and Level with the Inclusion of Wet 
Distillers Grains on Ruminal Metabolism and Nutrient Digestibility 
Josh R. Benton 
University of Nebraska-Lincoln 
Galen E. Erickson 
University of Nebraska-Lincoln, gerickson4@unl.edu 
Terry J. Klopfenstein 
University of Nebraska-Lincoln, tklopfenstein1@unl.edu 
Nathan F. Meyer 
University of Nebraska-Lincoln 
Crystal D. Buckner 
University of Nebraska-Lincoln, cbuckner2@unl.edu 
Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr 
 Part of the Animal Sciences Commons 
Benton, Josh R.; Erickson, Galen E.; Klopfenstein, Terry J.; Meyer, Nathan F.; and Buckner, Crystal D., 
"Effects of Roughage Source and Level with the Inclusion of Wet Distillers Grains on Ruminal Metabolism 
and Nutrient Digestibility" (2009). Nebraska Beef Cattle Reports. 509. 
https://digitalcommons.unl.edu/animalscinbcr/509 
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 73 
Effects of Roughage Source and Level with the Inclusion 
of Wet Distillers Grains on Ruminal Metabolism 
and Nutrient Digestibility
Josh R. Benton
Galen E. Erickson
Terry J. Klopfenstein
Nathan F. Meyer
Crystal D. Buckner1
Summary
Six ruminally cannulated steers were 
used in a 6 x 6 Latin square with treat-
ments arranged as a 2 x 3 factorial with 
alfalfa hay or cornstalks included at a 
normal, low or zero level on an equal 
neutral detergent fiber (NDF) basis. The 
base finishing diet contained 30% wet 
distillers grains plus solubles (WDGS). 
No source x level interactions were 
observed . Roughage source had no effect 
on nutrient intake, dry matter (DM) 
and organic matter (OM) digestibility 
or ruminal pH. Digestibility of NDF 
tended to be higher for alfalfa hay com-
pared to cornstalks. Ruminal pH, DMI 
and NDF intake increased linearly while 
nutrient digestibility decreased linearly 
as roughage level increased. These data 
indicate that in finishing diets con-
taining 30% wet distillers grains plus 
solubles (WDGS) roughages can be 
exchanged on an equal NDF basis and it 
is not beneficial to completely eliminate 
roughage sources from the diet.
Introduction
Roughages have been used to con-
trol acidosis in feedlot diets. However, 
corn-milling byproducts may help 
manage acidosis, suggesting rough-
ages may be reduced or eliminated. 
Roughage source and level were evalu-
ated and compared to no roughage 
inclusion in finishing diets contain-
ing 30% (DM basis) WDGS (2007 
Nebraska Beef Report, pp. 29-32). 
Higher roughage levels increased 
DMI and average daily gain (ADG), 
and elimination of roughage resulted 
in decreased DMI and ADG. Diets 
containing no roughage or low levels 
of cornstalks tended to have the low-
est feed-to-gain ratio (F:G). Overall, 
the previous study indicated that at 
high roughage levels, sources can be 
exchanged on an equal NDF basis in 
diets containing 30% WDGS. The 
objectives of the current study were 
to determine the effects of roughage 
source and level on nutrient digestion 
and ruminal fermentation character-
istics.
Procedure
Six ruminally cannulated steers 
(BW = 762 lb) were used in a 6 x 6 
Latin square to determine the effects 
of roughage source and level in feedlot 
diets containing WDGS. Treatments 
were arranged as a 2 x 3 factorial 
treatment structure with alfalfa hay 
included at 0%, 4% or 8% and corn-
stalks included at 0%, 3% or 6% on 
a DM basis (Table 1). Alfalfa and 
cornstalks averaged 57.2% and 78.8% 
NDF, respectively, and dietary treat-
ments were balanced to provide equal 
percentages of NDF from roughage at 
each level. All diets contained a mix-
ture of dry-rolled and high-moisture 
corn fed at a 1:1 ratio and 30% WDGS 
(DM basis). 
Periods were 14 days in length, 
including a 9-day adaptation period 
followed by a 5-day collection period 
to measure ruminal digestibility, fer-
mentation, pH and DMI. Steers were 
fed individually in pens during the 
adaptation period and moved into 
stanchions on day 9 for the collection 
period. Steers were fed once daily at 
0730, and feed refusals were collected 
daily if present. Chromic oxide (7.5g/
dose) was used as an indigestible 
marker for estimating fecal output 
and was dosed intraruminally at 0700 
and 1900 daily from day 6 through 
day 14 of each period. Fecal grab 
samples were collected three times 
daily during the collection period at 
0, 6 and 12 hours post-feeding. Feed 
intake patterns and ruminal pH mea-
surements were collected as described 
in the 1998 Nebraska Beef Report, 
pp. 71-75. Feed intake measurements 
included DMI, number of meals per 
day, total time spent eating and intake 
rate. Ruminal pH measurements 
included average, maximum and min-
imum pH, magnitude of pH change, 
pH variance, time spent below pH 5.6 
and 5.3, and area of pH below 5.6 and 
5.3 (time below x magnitude below). 
Feed ingredients, feed refusals and 
Table 1. Composition of finishing diets.1
Roughage Source  Alfalfa   Cornstalks
Roughage Level2: 0 4 8 0 3 6
DRC3 32.50 30.50 28.50 32.50 30.98 29.46
HMC3 32.50 30.50 28.50 32.50 30.98 26.46
WDGS3 30.0 30.0 30.0 30.0 30.0 30.0
Alfalfa hay — 4.00 8.00 — — —
Cornstalks — — — — 3.04 6.08
Dry supplement4 5.0 5.0 5.0 5.0 5.0 5.0
Roughage NDF, %5 0.00 2.62 5.25 0.00 2.56 5.11
1Values presented on a DM basis.
2Percent of diet DM.
3DRC = dry-rolled corn; HMC = high-moisture corn; WDGS = wet distillers grains plus solubles.
4All diets were formulated to contain a minimum of 0.65 % Ca, 0.60% K, 360 mg/steer daily 
Rumensin ®, 90mg/steer daily Tylan® and 130mg/steer daily thiamine.
5NDF supplied from roughage source included in the diet.
(Continued on next page)
Page 74 — 2009 Nebraska Beef Report  © The Board of Regents of the University of Nebraska.  All rights reserved.
fecal samples were freeze-dried for 
analysis to calculate nutrient digest-
ibility.
Data were analyzed as a 2 x 3 facto-
rial treatment arrangement and Latin 
square experimental design using the 
MIXED procedure of SAS. Period was 
included in the model as a fixed effect , 
and the random effect was steer. 
Ortho gonal contrasts were used to 
detect linear and quadratic relation-
ship for the main effect of roughage 
level if no interaction was detected. If 
an interaction occurred, only simple 
effects were tested.
Results
There were no effects on nutrient 
intake or digestibility due to roughage 
Table 2. Main effects of roughage source and level on nutrient intake and digestibility.
 Roughage Source  Roughage Level1    P-Value2
Item Alfalfa Cornstalks 0 3-4 6-8 SEM Source Lin. Quad.
Nutrient Digestibility
DM
 Intake, lb/day 20.9 20.6 19.4 20.9 21.9 1.4 0.73 0.05 0.83
 Digestibility, % 84.4 83.3 86.9 82.7 81.9 0.1 0.30 < 0.01 0.14
OM
 Intake, lb/day 20.5 19.4 19.1 20.5 20.2 0.60 0.23 0.33 0.37
 Digestibility, % 85.5 84.5 88.1 84.0 82.9 0.1 0.35 < 0.01 0.18
NDF
 Intake, lb/day 5.04 4.75 4.20 5.04 5.43 0.15 0.19 < 0.01 0.30
 Digestibility, % 75.9 72.9 77.3 73.1 72.8 0.1 0.10 0.06 0.31
Intake Patterns
 Meals/day 11.7 12.5 12.1 12.5 11.8 0.7 0.18 0.57 0.37
 Time eating/day, minutes 572 573 570 587 561 27 0.93 0.72 0.28
 Rate, %/hour 18.9 18.4 18.3 17.3 20.3 1.4 0.77 0.32 0.22
1Percent of diet DM.
2No differences (P > 0.20) due to roughage source x level interaction; Source = main effects of alfalfa versus cornstalks; Lin.= contrast for the linear effect of 
roughage inclusion level; Quad. = contrast for the quadratic effect of roughage inclusion level.
Table 3. Main effects of roughage source and level on ruminal pH.
 Roughage Source  Roughage Level1    P-Value2
Item Alfalfa Cornstalks 0 3-4 6-8 SEM Source Lin. Quad.
Average pH 5.48 5.52 5.31 5.49 5.70 0.12 0.74 0.01 0.93
Maximum pH 6.14 6.19 5.93 6.11 6.45 0.13 0.73 0.01 0.57
Minimum pH 4.82 4.94 4.47 5.10 5.08 0.22 0.59 0.05 0.17
pH change 1.31 1.24 1.45 1.01 1.37 0.25 0.87 0.80 0.16
pH variance 0.068 0.079 0.064 0.054 0.102 0.025 0.70 0.27 0.33
Time < 5.6, min/day 907 884 1116 919 652 168 0.89 0.02 0.81
Area < 5.6, min/day3 331 351 486 343 195 122 0.80 0.01 0.98
Time < 5.3, min/day 511 519 741 519 285 215 0.95 0.01 0.97
Area < 5.3, min/day3 119 139 208 123 56 67 0.65 0.02 0.84
1Percent of diet DM.
2No differences (P > 0.26) due to roughage source x level interaction; Source = main effects of alfalfa versus cornstalks; Lin.= contrast for the linear effect of 
roughage inclusion level; Quad. = contrast for the quadratic effect of roughage inclusion level.
3Area below pH of 5.6 or 5.3 is calculated as time below x magnitude below.
source x level interactions (P > 0.20); 
therefore, all nutrient intake and 
digestibility data are presented show-
ing only main effects of roughage 
source and level (Table 2). There were 
no differences (P > 0.18) for nutri-
ent intake and digestibility between 
alfalfa hay and cornstalks except for 
NDF digestibility, which tended to 
be higher (P = 0.10) for alfalfa hay 
(75.9%) compared to cornstalks 
(72.9%). Increasing roughage level 
resulted in a linear increase (P = 0.05) 
in DMI (19.4 lb to 21.9 lb) and NDF 
intake (1.91 lb to 2.47 lb). Organic 
matter intake was similar among 
roughage levels. As roughage level 
increased, there was a linear decrease 
in DM (86.9% to 81.9%), OM (88.1% 
to 82.9%) and NDF (77.3% to 72.8%) 
digestibility. There were no effects 
on intake patterns due to roughage 
source, roughage level or roughage 
source x level interaction. For alfalfa 
hay and cornstalks, intake rate was 
18.9% and 18.4%, respectively. Intake 
rate was 18.3%, 17.3% and 20.3% for 
zero, low and high roughage inclusion 
levels, respectively. 
There were no effects of rough-
age source or roughage source x level 
interaction on ruminal pH, so only 
main effects of roughage source and 
roughage level are presented in Table 
3. For alfalfa hay and cornstalks, 
ruminal pH averaged 5.48 and 5.52, 
respectively. Ruminal pH ranged from 
4.82 to 6.14 for alfalfa hay and from 
4.94 to 6.19 for cornstalks. Average, 
maximum and minimum ruminal 
© The Board of Regents of the University of Nebraska.  All rights reserved. 2009 Nebraska Beef Report  — Page 75 
pH increased linearly (P = 0.01) due 
to increasing roughage levels. The 
pH change or the difference between 
maximum and minimum pH, as 
well as pH variance remained fairly 
constant across roughage levels. Time 
spent below pH 5.6 or 5.3 and area 
below 5.6 and 5.3 both decreased 
linearly (P < 0.03) due to increasing 
roughage levels. A ruminal pH below 
5.6 is defined as subacute acidosis. For 
steers consuming diets containing 0% 
roughage, ruminal pH was below 5.6 
for 1116 minutes/day and below 5.3 
for 731 minutes/day. That corresponds 
to over 18 hours a day that these steers 
experienced subacute acidosis, and 
over 12 hours a day were spent at a pH 
of less than 5.3. When roughage levels 
were increased to 3-4% and 6-8%, 
time spent below pH 5.6 was reduced 
18% and 42%, respectively.
In conclusion, roughage source did 
not affect ruminal metabolism or in-
take patterns. These results agree with 
observations made in the previous 
finishing trial and indicate roughages 
can be exchanged on an equal NDF 
basis in finishing diets containing 
30% WDGS. Nutrient intake and 
ruminal pH increased linearly due 
to increasing roughage levels while 
nutrient digestibility decreased linear-
ly. When 0% roughage was included 
in the diet, DMI and ruminal pH were 
markedly reduced, compared to diets 
containing 3-8% roughage, which is 
in agreement with observations made 
in the previous finishing trial. These 
results further support the finding 
that it is not beneficial to completely 
eliminate roughage sources from a 
finishing diet containing 30% WDGS 
(DM basis). 
1Josh R. Benton, research technician; 
Galen E. Erickson, associate professor; Terry 
J. Klopfenstein, professor; Nathan F. Meyer, 
research technician; Crystal D. Buckner, research 
technician, Animal Science, Lincoln, Neb.


Effects of Roughage Source and Level with the Inclusion of Wet Distillers Grains on Ruminal Metabolism and Nutrient Digestibility

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Nebraska Beef Cattle Reports Animal Science Department 2009 Effects of Roughage Source and Level with the Inclusion of Wet Distillers Grains on Ruminal Metabolism and Nutrient Digestibility Josh R. Benton University of Nebraska-Lincoln Galen E. Erickson University of Nebraska-Lincoln, gerickson4@unl.edu Terry J. Klopfenstein University of Nebraska-Lincoln, tklopfenstein1@unl.edu Nathan F. Meyer University of Nebraska-Lincoln Crystal D. Buckner University of Nebraska-Lincoln, cbuckner2@unl.edu Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr  Part of the Animal Sciences Commons Benton, Josh R.; Erickson, Galen E.; Klopfenstein, Terry J.; Meyer, Nathan F.; and Buckner, Crystal D., "Effects of Roughage Source and Level with the Inclusion of Wet Distillers Grains on Ruminal Metabolism and Nutrient Digestibility" (2009). Nebraska Beef Cattle Reports. 509. https://digitalcommons.unl.edu/animalscinbcr/509 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 73 Effects of Roughage Source and Level with the Inclusion of Wet Distillers Grains on Ruminal Metabolism and Nutrient DigestibilityJosh R. BentonGalen E. EricksonTerry J. KlopfensteinNathan F. MeyerCrystal D. Buckner1SummarySix ruminally cannulated steers were used in a 6 x 6 Latin square with treat-ments arranged as a 2 x 3 factorial with alfalfa hay or cornstalks included at a normal, low or zero level on an equal neutral detergent fiber (NDF) basis. The base finishing diet contained 30% wet distillers grains plus solubles (WDGS). No source x level interactions were observed . Roughage source had no effect on nutrient intake, dry matter (DM) and organic matter (OM) digestibility or ruminal pH. Digestibility of NDF tended to be higher for alfalfa hay com-pared to cornstalks. Ruminal pH, DMI and NDF intake increased linearly while nutrient digestibility decreased linearly as roughage level increased. These data indicate that in finishing diets con-taining 30% wet distillers grains plus solubles (WDGS) roughages can be exchanged on an equal NDF basis and it is not beneficial to completely eliminate roughage sources from the diet.IntroductionRoughages have been used to con-trol acidosis in feedlot diets. However, corn-milling byproducts may help manage acidosis, suggesting rough-ages may be reduced or eliminated. Roughage source and level were evalu-ated and compared to no roughage inclusion in finishing diets contain-ing 30% (DM basis) WDGS (2007 Nebraska Beef Report, pp. 29-32). Higher roughage levels increased DMI and average daily gain (ADG), and elimination of roughage resulted in decreased DMI and ADG. Diets containing no roughage or low levels of cornstalks tended to have the low-est feed-to-gain ratio (F:G). Overall, the previous study indicated that at high roughage levels, sources can be exchanged on an equal NDF basis in diets containing 30% WDGS. The objectives of the current study were to determine the effects of roughage source and level on nutrient digestion and ruminal fermentation character-istics.ProcedureSix ruminally cannulated steers (BW = 762 lb) were used in a 6 x 6 Latin square to determine the effects of roughage source and level in feedlot diets containing WDGS. Treatments were arranged as a 2 x 3 factorial treatment structure with alfalfa hay included at 0%, 4% or 8% and corn-stalks included at 0%, 3% or 6% on a DM basis (Table 1). Alfalfa and cornstalks averaged 57.2% and 78.8% NDF, respectively, and dietary treat-ments were balanced to provide equal percentages of NDF from roughage at each level. All diets contained a mix-ture of dry-rolled and high-moisture corn fed at a 1:1 ratio and 30% WDGS (DM basis). Periods were 14 days in length, including a 9-day adaptation period followed by a 5-day collection period to measure ruminal digestibility, fer-mentation, pH and DMI. Steers were fed individually in pens during the adaptation period and moved into stanchions on day 9 for the collection period. Steers were fed once daily at 0730, and feed refusals were collected daily if present. Chromic oxide (7.5g/dose) was used as an indigestible marker for estimating fecal output and was dosed intraruminally at 0700 and 1900 daily from day 6 through day 14 of each period. Fecal grab samples were collected three times daily during the collection period at 0, 6 and 12 hours post-feeding. Feed intake patterns and ruminal pH mea-surements were collected as described in the 1998 Nebraska Beef Report, pp. 71-75. Feed intake measurements included DMI, number of meals per day, total time spent eating and intake rate. Ruminal pH measurements included average, maximum and min-imum pH, magnitude of pH change, pH variance, time spent below pH 5.6 and 5.3, and area of pH below 5.6 and 5.3 (time below x magnitude below). Feed ingredients, feed refusals and Table 1. Composition of finishing diets.1Roughage Source  Alfalfa   CornstalksRoughage Level2: 0 4 8 0 3 6DRC3 32.50 30.50 28.50 32.50 30.98 29.46HMC3 32.50 30.50 28.50 32.50 30.98 26.46WDGS3 30.0 30.0 30.0 30.0 30.0 30.0Alfalfa hay — 4.00 8.00 — — —Cornstalks — — — — 3.04 6.08Dry supplement4 5.0 5.0 5.0 5.0 5.0 5.0Roughage NDF, %5 0.00 2.62 5.25 0.00 2.56 5.111Values presented on a DM basis.2Percent of diet DM.3DRC = dry-rolled corn; HMC = high-moisture corn; WDGS = wet distillers grains plus solubles.4All diets were formulated to contain a minimum of 0.65 % Ca, 0.60% K, 360 mg/steer daily Rumensin ®, 90mg/steer daily Tylan® and 130mg/steer daily thiamine.5NDF supplied from roughage source included in the diet.(Continued on next page)Page 74 — 2009 Nebraska Beef Report  © The Board of Regents of the University of Nebraska.  All rights reserved.fecal samples were freeze-dried for analysis to calculate nutrient digest-ibility.Data were analyzed as a 2 x 3 facto-rial treatment arrangement and Latin square experimental design using the MIXED procedure of SAS. Period was included in the model as a fixed effect , and the random effect was steer. Ortho gonal contrasts were used to detect linear and quadratic relation-ship for the main effect of roughage level if no interaction was detected. If an interaction occurred, only simple effects were tested.ResultsThere were no effects on nutrient intake or digestibility due to roughage Table 2. Main effects of roughage source and level on nutrient intake and digestibility. Roughage Source  Roughage Level1    P-Value2Item Alfalfa Cornstalks 0 3-4 6-8 SEM Source Lin. Quad.Nutrient DigestibilityDM Intake, lb/day 20.9 20.6 19.4 20.9 21.9 1.4 0.73 0.05 0.83 Digestibility, % 84.4 83.3 86.9 82.7 81.9 0.1 0.30 < 0.01 0.14OM Intake, lb/day 20.5 19.4 19.1 20.5 20.2 0.60 0.23 0.33 0.37 Digestibility, % 85.5 84.5 88.1 84.0 82.9 0.1 0.35 < 0.01 0.18NDF Intake, lb/day 5.04 4.75 4.20 5.04 5.43 0.15 0.19 < 0.01 0.30 Digestibility, % 75.9 72.9 77.3 73.1 72.8 0.1 0.10 0.06 0.31Intake Patterns Meals/day 11.7 12.5 12.1 12.5 11.8 0.7 0.18 0.57 0.37 Time eating/day, minutes 572 573 570 587 561 27 0.93 0.72 0.28 Rate, %/hour 18.9 18.4 18.3 17.3 20.3 1.4 0.77 0.32 0.221Percent of diet DM.2No differences (P > 0.20) due to roughage source x level interaction; Source = main effects of alfalfa versus cornstalks; Lin.= contrast for the linear effect of roughage inclusion level; Quad. = contrast for the quadratic effect of roughage inclusion level.Table 3. Main effects of roughage source and level on ruminal pH. Roughage Source  Roughage Level1    P-Value2Item Alfalfa Cornstalks 0 3-4 6-8 SEM Source Lin. Quad.Average pH 5.48 5.52 5.31 5.49 5.70 0.12 0.74 0.01 0.93Maximum pH 6.14 6.19 5.93 6.11 6.45 0.13 0.73 0.01 0.57Minimum pH 4.82 4.94 4.47 5.10 5.08 0.22 0.59 0.05 0.17pH change 1.31 1.24 1.45 1.01 1.37 0.25 0.87 0.80 0.16pH variance 0.068 0.079 0.064 0.054 0.102 0.025 0.70 0.27 0.33Time < 5.6, min/day 907 884 1116 919 652 168 0.89 0.02 0.81Area < 5.6, min/day3 331 351 486 343 195 122 0.80 0.01 0.98Time < 5.3, min/day 511 519 741 519 285 215 0.95 0.01 0.97Area < 5.3, min/day3 119 139 208 123 56 67 0.65 0.02 0.841Percent of diet DM.2No differences (P > 0.26) due to roughage source x level interaction; Source = main effects of alfalfa versus cornstalks; Lin.= contrast for the linear effect of roughage inclusion level; Quad. = contrast for the quadratic effect of roughage inclusion level.3Area below pH of 5.6 or 5.3 is calculated as time below x magnitude below.source x level interactions (P > 0.20); therefore, all nutrient intake and digestibility data are presented show-ing only main effects of roughage source and level (Table 2). There were no differences (P > 0.18) for nutri-ent intake and digestibility between alfalfa hay and cornstalks except for NDF digestibility, which tended to be higher (P = 0.10) for alfalfa hay (75.9%) compared to cornstalks (72.9%). Increasing roughage level resulted in a linear increase (P = 0.05) in DMI (19.4 lb to 21.9 lb) and NDF intake (1.91 lb to 2.47 lb). Organic matter intake was similar among roughage levels. As roughage level increased, there was a linear decrease in DM (86.9% to 81.9%), OM (88.1% to 82.9%) and NDF (77.3% to 72.8%) digestibility. There were no effects on intake patterns due to roughage source, roughage level or roughage source x level interaction. For alfalfa hay and cornstalks, intake rate was 18.9% and 18.4%, respectively. Intake rate was 18.3%, 17.3% and 20.3% for zero, low and high roughage inclusion levels, respectively. There were no effects of rough-age source or roughage source x level interaction on ruminal pH, so only main effects of roughage source and roughage level are presented in Table 3. For alfalfa hay and cornstalks, ruminal pH averaged 5.48 and 5.52, respectively. Ruminal pH ranged from 4.82 to 6.14 for alfalfa hay and from 4.94 to 6.19 for cornstalks. Average, maximum and minimum ruminal © The Board of Regents of the University of Nebraska.  All rights reserved. 2009 Nebraska Beef Report  — Page 75 pH increased linearly (P = 0.01) due to increasing roughage levels. The pH change or the difference between maximum and minimum pH, as well as pH variance remained fairly constant across roughage levels. Time spent below pH 5.6 or 5.3 and area below 5.6 and 5.3 both decreased linearly (P < 0.03) due to increasing roughage levels. A ruminal pH below 5.6 is defined as subacute acidosis. For steers consuming diets containing 0% roughage, ruminal pH was below 5.6 for 1116 minutes/day and below 5.3 for 731 minutes/day. That corresponds to over 18 hours a day that these steers experienced subacute acidosis, and over 12 hours a day were spent at a pH of less than 5.3. When roughage levels were increased to 3-4% and 6-8%, time spent below pH 5.6 was reduced 18% and 42%, respectively.In conclusion, roughage source did not affect ruminal metabolism or in-take patterns. These results agree with observations made in the previous finishing trial and indicate roughages can be exchanged on an equal NDF basis in finishing diets containing 30% WDGS. Nutrient intake and ruminal pH increased linearly due to increasing roughage levels while nutrient digestibility decreased linear-ly. When 0% roughage was included in the diet, DMI and ruminal pH were markedly reduced, compared to diets containing 3-8% roughage, which is in agreement with observations made in the previous finishing trial. These results further support the finding that it is not beneficial to completely eliminate roughage sources from a finishing diet containing 30% WDGS (DM basis). 1Josh R. Benton, research technician; Galen E. Erickson, associate professor; Terry J. Klopfenstein, professor; Nathan F. Meyer, research technician; Crystal D. Buckner, research technician, Animal Science, Lincoln, Neb.

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Effects of Roughage Source and Level with the Inclusion of Wet Distillers Grains on Ruminal Metabolism and Nutrient Digestibility

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