Dried distillers grains and(or) soybean hulls to background beef calves fed bahiagrass forage

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Dried distillers grains and(or) soybean hulls to background beef calves fed bahiagrass forage
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2009 Florida Beef Report
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Wahrmund, Jacqueline
Hersom, Matt
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Institute of Food and Agricultural Sciences, University of Florida
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Gainesville, Fla.
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Dried Distillers Grains and(or) Soybean Hulls to Background Beef Calves Fed
Bahiagrass Forage

Jacqueline Wahrmund
Matt Hersom1


Summary
The objective of this study was to determine the
effects of i yl. ,iii /m ig dried distillers grains
soybean hulls, or combinations of the two to
growing beef steers consuming bahiagrass hay.
Angus steers were randomly allotted to one of
four supplement treatments. Treatments
included: 1) dried distillers grains; 2) dried
distillers grains/soybean hulls; 3) soybean
hulls/distillers grains; 4) soybean hulls.
Supplements were formulated to be :"' .. ,g, t,,.
and steers were individually supplemented via a
Calan Gate system for 42 d. All steers were
allowed ad libitum access to bahiagrass hay.
Supplement treatment had no effect on final
i, ,h i.-hti From d 0 to 14, average daily gain
(ADG) of dried distillers grains supplemented
steers was 0.59 lb/d less compared to any
treatments containing soybean hulls. Across all
42 d, ADG of soybean hull supplemented steers
was less than the combinations of dried distillers
grains and soybean hulls, but was not different
than steers supplemented with dried distillers
grains only. Plasma glucose concentrations
were not different between supplement
treatments. On d 0, plasma urea nitrogen
concentration did not differ between treatments.
However, on d 14, 28, and 42 the plasma
urea nitrogen concentrations of steers offered
supplements containing dried distillers grains
were greater compared to steers offered
supplements containing soybean hulls.
S'uppl ,11 m, /Ig steers consuming bahiagrass hay
with a combination of co-products resulted in


improved ADG gain and nitrogen metabolism.
The combination of 2.11 lb of dried distillers
grains and 4.52 lb of soybean hulls optimized
calf performance.

Introduction
Bahiagrass is the most common type of forage
utilized in Florida (Chambliss and Sollenberger,
1991); however, cattle are not able to consume
enough bahiagrass to meet their nutrient
requirements at certain points of the production
cycle. Therefore, supplementation programs
must be developed to optimize beef cattle
performance. Bahiagrass in Florida generally
does not contain enough protein to meet growing
beef cattle requirements.

Low-quality tropical and subtropical grass
forages are often deficient in crude protein (CP)
relative to the protein requirements of many
classes of cattle. Therefore, cattle with greater
protein requirements, such as growing cattle,
will require additional protein supplementation
to meet the nutritional demands associated with
growth when maintained on a high-forage diet.
Dried distillers grains (DDG) are a co-product of
the corn-derived ethanol fuel industry. As
ethanol fuel production continues to increase in
the United States, DDG will become more
available to cattle producers for animal
consumption. Soybean hulls (SBH) are another
readily available co-product. The price of the
feedstuffs, as well as the nutrient needs of the


2009 Florida BeefReport


Co-products dried distillers grains or soybean hulls can be utilized as supplements for growing beef
cattle. Combinations of the two ingredients resulted in the best growth performance compared to the
individual ingredients. The price of each co-product should determine the most economic proportion of
the co-products fed.










cattle, will generally dictate the most
economically desirable supplementation program
to optimize herd performance. Combinations of
DDG and SBH were fed to determine practical
feeding applications of these two co-products.


Materials and Methods
Animals and Diets
Fifty-six Angus steers were blocked by
bodyweight (BW) and randomly assigned to one
of four treatments and one of seven pens.
Treatments included: 1) DDG (6.17 lb of DM);
2) DDG/SBH (4.25 lb DDG, 2.16 lb SBH); 3)
SBH/DDG (2.11 lb DDG, 4.52 lb SBH); 4) SBH
(6.87 lb of DM). All steers were fed
approximately 5.95 lb of SBH for five d prior to
the initiation of the trial. Supplement treatments
began on d 0 after sampling. Bahiagrass hay
was offered to each pen, ad libitum, as large
round bales. Fresh bales were offered each wk,
and each bale was weighed and core-sampled for
analysis of chemical composition. Steers were
individually supplemented at approximately
0700 via a Calan gate system.

Sampling and Analysis
Steers were fed for 42 d, unshrunk BW were
taken on two consecutive d at the initiation (d -1,
0) and termination of the trial (d 42, 43).
Interim BW were obtained on d 14 and 28. The
two-d mean of BW was utilized to determine
initial and final BW and ADG. Blood samples
were collect for analysis of plasma urea nitrogen
(PUN) and glucose concentrations. Bodyweight
measurements and blood samples were obtained
prior to supplements being offered.

Weekly hay samples were collected from each
pen and composite for analysis of chemical
composition. Hay and supplement total
digestible nutrients (TDN) concentrations were
determined using the equation (Fike et al.,
2002):

%TDN = [(% IVDMD 0.59) + 32.2] *
organic matter concentration.

Because hay was fed as large round bales within
each pen, mean daily hay dry matter intake
(DMI) was calculated using the NRC (2000)
equation:
SBW = 13.91 REO9116 EQSBW-0 6837


where:
SBW = shrunk body weight
RE = retained energy
EQSBW = equivalent shrunk body
weight,
assuming a 4% shrink, and that RE is
equal to net energy for gain (NEg).

Statistical Analysis
The experiment was designed as a completely
randomized design, with supplement treatment
as the fixed effect (Littell et al., 2006), steer
within treatment as the random effect, and
individual steer was the experimental unit. Data
were analyzed using the Mixed procedure of
SAS v9.1 (2002, SAS Inst., Inc., Cary, NC).
Means were calculated using least squares
means, and means were separated using the P-
diff option when the overall F-value was <0.10.

Results
Steer Performance and Intake
At the initiation of the trial, steer BW (mean 605
lb, Table 1) did not differ (P=0.99) among
treatments. Between d 0 and 14, steers
supplemented with DDG gained 55% less
(P<0.05) than steers on all other treatments.
Average daily gain from d 14 to 28 was not
different (P=0.55) among treatments. At the
completion of the study on d 42, final steer BW
was not different (P=0.79, mean = 674 lb).
From d 28 to 42, ADG did not differ (P=0.26)
among treatments; however, there was a
tendency (P=0.10) for treatment to affect overall
ADG from d 0 to 42. Steers consuming SBH
alone gained 0.37 lb/d less than steers
consuming SBH/DDG, and 0.31 lb/d less than
steers consuming DDG/SBH (P<0.05).

Supplement type affected (P=0.01) mean
estimated hay DMI (Table 1); steers
supplemented with only SBH consumed the
greatest amount of hay across the 42-d
experiment (8.48 lb/d), followed by steers
offered the SBH/DDG and DDG treatments,
which were not different (P>0.10). Differences
were also observed (P<0.05) in estimated total
DMI (Table 1), with steers offered SBH or
SBH/DDG consuming 24% more DM compared
to steers offered DDG or mostly DDG/SBH.

Gain:feed (Table 1) was calculated utilizing


2009 Florida BeefReport









mean estimated daily hay DMI and the amount
of supplement offered, with treatment affecting
(P<0.001) gain efficiency. Steers consuming
DDG/SBH were most efficient (P<0.05),
followed by the DDG and SBH/DDG
treatments, which were not different (P>0.10).
Steers supplemented with SBH only were least
efficient, with a gain efficiency of 0.03 less than
steers supplemented with DDG and SBH/DDG,
and 0.05 less than steers supplemented with
DDG/SBH (P<0.05).

Steers consuming DDG or SBH/DDG averaged
0.018 fewer (P<0.05) lb of gain per lb of feed
compared to steers consuming DDG/SBH.

Physiological Response
Prior to the initiation of the experiment, steers
were supplemented with approximately 5.95 lb/d
of SBH for five d. As a result, no treatment
differences (P=0.68) were observed in PUN
concentrations on d 0 (Table 2). However, on d
14, PUN concentration increased (P<0.01) as the
amount of DDG offered in the supplement
increased. Steers supplemented with only SBH
had a mean PUN concentration of 5.31 mg/dL.
Substituting a small amount of energy from
SBH with DDG resulted in an 85% increase
(P<0.05) in PUN concentrations of steers on the
SBH/DDG treatment, whereas, steers
supplemented with the DDG/SBH treatment had
24% greater (P<0.05) PUN concentrations
compared to steers offered SBH/DDG. Steers
supplemented with DDG had the greatest
(P<0.05) PUN concentrations, with 36.9%
greater concentrations compared to DDG/SBH-
supplemented steers. Similar patterns were
observed on d 28; PUN concentrations increased
(P<0.001) with the amount of DDG in the diet.
Treatment differences were observed (P<0.001)
on d 42. Steers consuming DDG only had the
greatest PUN concentrations; however,
differences were not observed (P>0.10) between
steers consuming the DDG and DDG/SBH
treatments. Additionally, there were no
differences (P>0.10) between steers on the
DDG/SBH and SBH/DDG treatments. Steers
supplemented with SBH had the lowest PUN
concentration (P<0.05).

The effects of treatment on steer PUN were
directly related to the amount of supplemental
protein offered. Total dietary N intake was


greatest (P<0.001; Table 1) for steers on the
only DDG diet, and decreased with the amount
of DDG offered, with steers offered only SBH
consuming the least amount of N/d. The greater
supply of dietary N resulted in greater amounts
of N metabolized, which appeared in the blood
as PUN. Hammond et al. (1993) suggested that
PUN concentrations above 12 mg/dL indicate
adequate dietary CP, and cattle may benefit from
energy supplementation in this situation.
Furthermore, PUN concentrations below 9
mg/dL indicate that dietary protein is
inadequate, and protein supplements may
enhance cattle performance. The steers offered
only DDG consistently had PUN concentrations
in excess of 12 mg/dL, and therefore, additional
dietary energy may have improved performance.
Additionally, steers offered only SBH never
achieved PUN concentrations above 7 mg/dL,
which indicates that protein was not sufficient to
maximize steer performance. The steers that
received a combination of co-products had PUN
concentrations that ranged from 8.4 mg/dL to
12.1 mg/dL throughout the experiment after d 0.
These results further illustrate the metabolic
advantage of supplemental protein and energy,
which tended to improve overall ADG above the
SBH supplement, and increased gain efficiency
in steers offered the DDG/SBH treatment.

There were no treatment differences (P>0.78) in
plasma glucose concentrations on d 0, 14, 28,
and 42. Plasma glucose concentrations have
been shown to be related to energy intake
(Schmidt and Keith, 1983); however, differences
in total TDN intake by steers in this trial (Table
1) did not affect plasma glucose.

Economic Analysis
A simple economic analysis was conducted to
determine the most desirable supplement
combination for producers (Table 3). The prices
paid for the feedstuffs were as follows: hay,
$30/bale; DDG, $182/T; SBH, $155/T. Based
on the prices paid for the supplements, the
cost/lb of each supplement were as follows:
DDG, $0.091; DDG/SBH, $0.086; SBH/DDG,
$0.082; SBH, $0.077. The cost of BW gain was
determined based on the cost of total feed.
Steers consuming the SBH treatment had the
greatest (P<0.05) cost of BW gain at $0.681/lb,
compared to the other three treatments which
ranged from $0.499/lb to $0.590/lb. The SBH


2009 Florida BeefReport










were the least economically efficient as a result
of their low BW gains and high hay intakes.
These results may indicate that the combinations
of co-products were more cost efficient
compared to DDG or SBH alone. The price of
each co-product should determine the most
economically desirable proportions of DDG and
SBH used to background steers.

The combination of mostly DDG was the most
efficient and economical supplement. The other
two supplements containing DDG also
outperformed the SBH only diet. Therefore, the
SBH treatment alone is not a desirable
supplement to growing steers when fed at this
level or in combination with this hay. Growing
steers require more protein than they are able to
consume from a diet of bahiagrass hay with
SBH supplementation. The cost of the co-
product supplements should dictate the most
desirable combinations to feed to growing beef
steers.








Literature Cited
Chambliss and Sollenberger. 1991. Pages 74-80 in Proc. 40th Florida Beef Cattle Short Course.
Fike et al. 2002. J. Dairy Sci. 85:866-878.
Hammond et al. 1993. In: Proc. XVII Int. Grassl. Con r. p 1989.
Littell et al. 2006. SAS System for Mixed Models. 2n ed.
NRC. 2000. Nutrient requirements of beef cattle. 7th rev. ed.











1 Jacqueline Wahrmund, Former Graduate Student, Matt Hersom, Assistant Professor, UF-IFAS, Department
of Animal Sciences, Gainesville, FL.


2009 Florida BeefReport










Table 1. Effect of dried distillers grains (DDG) and/or soybean hulls (SBH) supplementation on steer
bodyweight (BW), BW gain and intake.
Treatment
Item DDG DDG/SBH SBH/DDG SBH SEMb P-value
Initial BW, lb 604 608 606 600 16.0 0.99

BW gain, lb/d
d 0 14 0.73d 1.19de 1.37e 1.39e 0.18 0.03
d 14 28 1.98 2.07 1.78 1.48 0.31 0.55
d 28 42 2.05 2.07 2.36 1.50 0.31 0.26
d 0 42 1.59de 1.76d 1.83d 1.45e 0.11 0.10

Mean hay DMI, lb/d 6.01de 5.64d 7.67ef 8.48f 0.64 0.01
Total DMI, lb/d 11.45d 11.32d 13.57e 14.60e 0.64 0.001
N Intake, g/dc 180.45d 154.67e 142.40f 122.15g 4.48 <0.001
TDN Intake, lb/d' 8.50d 8.79d 8.92e 7.73f 0.20 <0.001

Gain:Feed 0.12d 0.14e 0.12d 0.09f 0.01 <0.001
a Least square means; Treatment: DDG, 6.17 lb dried distillers grains; DDG/SBH, 4.25 lb DDG, 2.16 lb
soybean hulls; SBH/DDG, 2.11 lb DDG, 4.52 lb SBH; SBH, 6.87 lb SBH.
b Standard error of the mean, n=56.
' Estimated total dietary intake (hay and supplement).
d, e, f, g Means with different superscripts within a row are different (P<0.05).


Table 2. Effect of dried distillers grains (DDG) and/or soybean hulls (SBH) supplementation on steer
plasma glucose and urea nitrogen concentration.
Treatment
Item DDG DDG/SBH SBH/DDG SBH SEMb P-value
PUN', mg/dL
d 0 6.75 6.17 6.13 6.44 0.41 0.68
d 14 16.57d 12.10e 9.80f 5.31g 0.81 <0.001
d28 14.01d 11.55e 8.42f 5.64g 0.70 <0.001
d 42 12.53d 11.86de 10.24e 5.86f 0.83 <0.001

Glucose, mg/dL
d 0 77.24 74.49 75.19 74.51 3.69 0.94
d 14 78.88 76.30 79.56 76.64 3.92 0.90
d28 80.38 75.69 76.25 76.29 4.06 0.83
d 42 80.76 75.82 76.79 75.66 4.29 0.78
a Least square means; Treatment: DDG, 6.17 lb dried distillers grains; DDG/SBH, 4.25 lb DDG, 2.16 lb
soybean hulls; SBH/DDG, 2.11 lb DDG, 4.52 lb SBH; SBH, 6.87 lb SBH.
b Standard error of the mean, n=56.
' Plasma urea nitrogen.
d, e, f, g Means with different superscripts within a row are different (P<0.05).


2009 Florida BeefReport










Table 3. Economics of supplementing dried distillers grains (DDG) or soybean hulls (SBH).
Treatment
Item DDG DDG/SBH SBH/DDG SBH SEMb P-value
Supplement cost, $/lbc 0.091 0.086 0.082 0.077 --- ---
Feed cost, $/steer/dd 0.89ef 0.92e 0.95' 0.87' 0.01 0.07
Total feed, $/steer 37.43et 38.83e 39.911 36.531 2.53 0.07
Cost of gain, $/lb BW 0.590e 0.499' 0.554ef 0.681g 0.03 0.003
gain/steer
a Least square means; Treatment: DDG, 6.17 lb dried distillers grains; DDG/SBH, 4.25 lb DDG,
2.16 lb soybean hulls; SBH/DDG, 2.11 lb DDG, 4.52 lb SBH; SBH, 6.87 lb SBH.
b Standard error of the mean, n=56.
c Cost of supplements: $182/T DDG, $155/T SBH.
d Cost of hay and supplement consumed per steer/d; hay cost, $30/bale.
e f' g Means with different superscripts within a row are different (P<0.05).


2009 Florida BeefReport




Full Text

PAGE 1

Dried Distillers Grains and(or) Soybean Hulls to Background Beef Calves Fed Bahiagrass Forage Jacqueline Wahrmund Matt Hersom 1 Summary The objective of this study was to determine the effects of supplementing dried distillers grains soybean hulls, or combinations of the two to growing beef steers consuming bahiagrass hay. Angus steers were randomly allotted to one of four supplement treatments. Treatments included: 1) dried distillers grains; 2) dried distillers grains/soybean hulls; 3) soybean hulls/distillers grains; 4) soybean hulls. Supplements were formulated to be isoenergetic, and steers were individually supplemented via a Calan Gate system for 42 d. All steers were allowed ad libitum access to bahiagrass hay. Supplement treatment had no effect on final bodyweight. From d 0 to 14, average daily gain (ADG) of dried distillers grains supplemented steers was 0.59 lb/d less compared to any treatments containing soybean hulls. Across all 42 d, ADG of soybean hull supplemented steers was less than the combinations of dried distillers grains and soybean hulls, but was not different than steers supplemented with dried distillers grains only. Plasma glucose concentrations were not different between supplement treatments. On d 0, plasma urea nitrogen concentration did not differ between treatments. However, on d 14, 28, and 42 the plasma urea nitrogen concentrations of steers offered supplements containing dried distillers grains were greater compared to steers offered supplements containing soybean hulls. Supplementing steers consuming bahiagrass hay with a combination of co -products resulted in improved ADG gain and nitrogen metabolism. The combination of 2.11 lb of dried distillers grains and 4.52 lb of soybean hulls optimized calf performance. Introduction Bahiagrass is the most common type of forage utilized in Florida (Chambliss and Sollenberger, 1991); however, cattle are not able to consume enough bahiagrass to meet their nutrient requirements at certain points of the production cycle. Therefore, supplementation programs must be developed to optimize beef cattle performance. Bahiagrass in Florida generally does not contain enough protein to meet growing beef cattle requirements. Low-quality tropical and subtropical grass forages are often deficient in crude protein ( CP ) relative to the protein requirements of many classes of cattle. Therefore, cattle with greater protein requirements, such as growing cattle, will require additional protein supplementation to meet the nutritional demands associated with growth when maintained on a high-forage diet. Dried distillers grains ( DDG) are a co-product of the corn-derived ethanol fuel industry. As ethanol fuel production continues to increase in the United States, DDG will become more available to cattle producers for animal consumption. Soybean hulls (SBH) are another readily available co-product. The price of the feedstuffs, as well as the nutrient needs of the Co products dried distillers grains or soybean hulls can be utilized as supplements for growing beef cattle. Combinations of the two ingredients resulted in the best growth performance compared to the individual ingredients. The price of each co product should determine the most ec onomic proportion of the co products fed.

PAGE 2

cattle, will generally dictate the most economically desirable supplementation program to optimize herd performance. Combinations of DDG and SBH were fed to determine practical feeding applications of these two co-products. Materials and Methods Animals and Diets Fifty-six Angus steers were blocked by bodyweight (BW) and randomly assigned to one of four treatments and one of seven pens. Treatments included: 1) DDG (6.17 lb of DM); 2) DDG/SBH (4.25 lb DDG, 2.16 lb SBH); 3) SBH/DDG (2.11 lb DDG, 4.52 lb SBH); 4) SBH (6.87 lb of DM). All steers were fed approximately 5.95 lb of SBH for five d prior to the initiation of the trial. Supplement treatments began on d 0 after sampling. Bahiagrass hay was offered to each pen, ad libitum, as large round bales. Fresh bales were offered each wk, and each bale was weighed and core-sampled for analysis of chemical composition. Steers were individually supplemented at approximately 0700 via a Calan gate system. Sampling and Analysis Steers were fed for 42 d, unshrunk BW were taken on two consecutive d at the initiation (d -1, 0) and termination of the trial (d 42, 43). Interim BW were obtained on d 14 and 28. The two-d mean of BW was utilized to determine initial and final BW and ADG. Blood samples were collect for analysis of plasma urea nitrogen (PUN) and glucose concentrations. Bodyweight measurements and blood samples were obtained prior to supplements being offered. Weekly hay samples were collected from each pen and composited for analysis of chemical composition. Hay and supplement total digestible nutrients (TDN) concentrations were determined using the equation (Fike et al., 2002): %TDN = [(% IVDMD 0.59) + 32.2] organic matter concentration. Because hay was fed as large round bales within each pen, mean daily hay dry matter intake (DMI) was calculated using the NRC (2000) equation: SBW = 13.91 RE 0.9116 EQSBW -0.6837 where: SBW = shrunk body weight RE = retained energy EQSBW = equivalent shrunk body weight, assuming a 4% shrink, and that RE is equal to net energy for gain (NE g ). Statistical Analysis The experiment was designed as a completely randomized design, with supplement treatment as the fixed effect (Littell et al., 2006), steer within treatment as the random effect, and individual steer was the experimental unit. Data were analyzed using the Mixed procedure of SAS v9.1 (2002, SAS Inst., Inc., Cary, NC). Means were calculated using least squares means, and means were separated using the Pdiff option when the overall F-value was <0.10. Results Steer Performance and Intake At the initiation of the trial, steer BW (mean 605 lb, Table 1) did not differ ( P =0.99) among treatments. Between d 0 and 14, steers supplemented with DDG gained 55% less ( P<0.05) than steers on all other treatments. Average daily gain from d 14 to 28 was not different ( P =0.55) among treatments. At the completion of the study on d 42, final steer BW was not different ( P =0.79, mean = 674 lb). From d 28 to 42, ADG did not differ ( P =0.26) among treatments; however, there was a tendency ( P =0.10) for treatment to affect overall ADG from d 0 to 42. Steers consuming SBH alone gained 0.37 lb/d less than steers consuming SBH/DDG, and 0.31 lb/d less than steers consuming DDG/SBH ( P <0.05). Supplement type affected ( P =0.01) mean estimated hay DMI (Table 1); steers supplemented with only SBH consumed the greatest amount of hay across the 42-d experiment (8.48 lb/d), followed by steers offered the SBH/DDG and DDG treatments, which were not different ( P >0.10). Differences were also observed ( P <0.05) in estimated total DMI (Table 1), with steers offered SBH or SBH/DDG consuming 24% more DM compared to steers offered DDG or mostly DDG/SBH. Gain:feed (Table 1) was calculated utilizing

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mean estimated daily hay DMI and the amount of supplement offered, with treatment affecting ( P <0.001) gain efficiency. Steers consuming DDG/SBH were most efficient ( P <0.05), followed by the DDG and SBH/DDG treatments, which were not different ( P >0.10). Steers supplemented with SBH only were least efficient, with a gain efficiency of 0.03 less than steers supplemented with DDG and SBH/DDG, and 0.05 less than steers supplemented with DDG/SBH ( P <0.05). Steers consuming DDG or SBH/DDG averaged 0.018 fewer ( P <0.05) lb of gain per lb of feed compared to steers consuming DDG/SBH. Physiological Response Prior to the initiation of the experiment, steers were supplemented with approximately 5.95 lb/d of SBH for five d. As a result, no treatment differences ( P =0.68) were observed in PUN concentrations on d 0 (Table 2). However, on d 14, PUN concentration increased ( P <0.01) as the amount of DDG offered in the supplement increased. Steers supplemented with only SBH had a mean PUN concentration of 5.31 mg/dL. Substituting a small amount of energy from SBH with DDG resulted in an 85% increase ( P <0.05) in PUN concentrations of steers on the SBH/DDG treatment, whereas, steers supplemented with the DDG/SBH treatment had 24% greater ( P <0.05) PUN concentrations compared to steers offered SBH/DDG. Steers supplemented with DDG had the greatest ( P <0.05) PUN concentrations, with 36.9% greater concentrations compared to DDG/SBHsupplemented steers. Similar patterns were observed on d 28; PUN concentrations increase d ( P <0.001) with the amount of DDG in the diet. Treatment differences were observed ( P <0.001) on d 42. Steers consuming DDG only had the greatest PUN concentrations; however, differences were not observed ( P >0.10) between steers consuming the DDG and DDG/SBH treatments. Additionally, there were no differences ( P >0.10) between steers on the DDG/SBH and SBH/DDG treatments. Steers supplemented with SBH had the lowest PUN concentration ( P <0.05). The effects of treatment on steer PUN were directly related to the amount of supplemental protein offered. Total dietary N intake was greatest ( P <0.001; Table 1) for steers on the only DDG diet, and decreased with the amount of DDG offered, with steers offered only SBH consuming the least amount of N/d. The greater supply of dietary N resulted in greater amounts of N metabolized, which appeared in the blood as PUN. Hammond et al. (1993) suggested that PUN concentrations above 12 mg/dL indicate adequate dietary CP, and cattle may benefit from energy supplementation in this situation. Furthermore, PUN concentrations below 9 mg/dL indicate that dietary protein is inadequate, and protein supplements may enhance cattle performance. The steers offered only DDG consistently had PUN concentrations in excess of 12 mg/dL, and therefore, additional dietary energy may have improved performance. Additionally, steers offered only SBH never achieved PUN concentrations above 7 mg/dL, which indicates that protein was not sufficient to maximize steer performance. The steers tha t received a combination of co-products had PUN concentrations that ranged from 8.4 mg/dL to 12.1 mg/dL throughout the experiment after d 0. These results further illustrate the metabolic advantage of supplemental protein and energy, which tended to improve overall ADG above the SBH supplement, and increased gain efficiency in steers offered the DDG/SBH treatment. There were no treatment differences ( P plasma glucose concentrations on d 0, 14, 28, and 42. Plasma glucose concentrations have been shown to be related to energy intake (Schmidt and Keith, 1983); however, differences in total TDN intake by steers in this trial (Table 1) did not affect plasma glucose. Economic Analysis A simple economic analysis was conducted to determine the most desirable supplement combination for producers (Table 3). The prices paid for the feedstuffs were as follows: hay, $30/bale; DDG, $182/T; SBH, $155/T. Based on the prices paid for the supplements, the cost/lb of each supplement were as follows: DDG, $0.091; DDG/SBH, $0.086; SBH/DDG, $0.082; SBH, $0.077. The cost of BW gain was determined based on the cost of total feed. Steers consuming the SBH treatment had the greatest ( P <0.05) cost of BW gain at $0.681/lb, compared to the other three treatments which ranged from $0.499/lb to $0.590/lb. The SBH

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were the least economically efficient as a result of their low BW gains and high hay intakes. These results may indicate that the combinations of co-products were more cost efficient compared to DDG or SBH alone. The price of each co-product should determine the most economically desirable proportions of DDG and SBH used to background steers. The combination of mostly DDG was the most efficient and economical supplement. The other two supplements containing DDG also outperformed the SBH only diet. Therefore, the SBH treatment alone is not a desirable supplement to growing steers when fed at this level or in combination with this hay. Growing steers require more protein than they are able to consume from a diet of bahiagrass hay with SBH supplementation. The cost of the coproduct supplements should dictate the most desirable combinations to feed to growing beef steers. Literature Cited Chambliss and Sollenberger. 1991. Pages 74 80 in Proc. 40 th Florida Beef Cattle Short Course. Fike et al. 2002. J. Dairy Sci. 85:866 878. Hammond et al. 1993. In: Proc. XVII Int. Grassl. Congr. p 1989. Littell et al 2006. SAS System for Mixed Models. 2 nd ed. NRC. 2000. Nutrient requirements of bee f cattle. 7 th rev. ed. 1 Jacqueline Wahrmund, Former Graduate Student, Matt Hersom, Assistant Professor, UF IFAS, Department of Animal Sciences, Gainesville, FL.

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Table 1 Effect of dried distillers grains (DDG) and/or soybean hulls (SBH) suppl ementation on steer bodyweight (BW), BW gain and intake. Treatment a Item DDG DDG/SBH SBH/DDG SBH SEM b P value Initial BW, lb 604 608 606 600 16.0 0.99 BW gain, lb/d d 0 14 0.73 d 1.19 de 1.37 e 1.39 e 0.18 0.03 d 14 28 1.98 2.07 1.78 1.48 0.31 0.55 d 28 42 2.05 2.07 2.36 1.50 0.31 0.26 d 0 42 1.59 de 1.76 d 1.83 d 1.45 e 0.11 0.10 Mean hay DMI, lb/d 6.01 de 5.64 d 7.67 ef 8.48 f 0.64 0.01 Total DMI, lb/d 11.45 d 11.32 d 13.57 e 14.60 e 0.64 0.001 N Intake, g/d c 180.45 d 154.67 e 142.40 f 122.15 g 4.48 <0.001 TDN Intake, lb/d c 8.50 d 8.79 d 8.92 e 7.73 f 0.20 <0.001 Gain:Feed 0.12 d 0.14 e 0.12 d 0.09 f 0.01 <0.001 a Least square means; Treatment: DDG, 6.17 lb dried distillers grains; DDG/SBH, 4.25 lb DDG, 2.16 lb soybean hulls; SBH/DDG, 2.11 lb DDG, 4.52 lb SBH; SBH, 6.87 lb SBH. b Standard error of the mean, n=56. c Estimated total dietary intake (hay and supplement). d, e, f, g Means with different superscripts within a row are different ( P <0.05). Table 2 Effect of dried distillers grains (DDG) and/or soybean hulls (SBH) supplementation on steer plasma glucose and urea nitrogen concentration. Treatment a Item DDG DDG/SBH SBH/DDG SBH SEM b P value PUN c mg/dL d 0 6.75 6.17 6.13 6.44 0.41 0.68 d 14 16.57 d 12.10 e 9.80 f 5.31 g 0.81 <0.001 d 28 14.01 d 11.55 e 8.42 f 5.64 g 0.70 <0.001 d 42 12.53 d 11.86 de 10.24 e 5.86 f 0.83 <0.001 Glucose, mg/dL d 0 77.24 74.49 75.19 74.51 3.69 0.94 d 14 78.88 76.30 79.56 76.64 3.92 0.90 d 28 80.38 75.69 76.25 76.29 4.06 0.83 d 42 80.76 75.82 76.79 75.66 4.29 0.78 a Least square means; Treatment: DDG, 6.17 lb dried distillers grains; DDG/SBH, 4.25 lb DDG, 2.16 lb soybean hulls; SBH/DDG, 2.11 lb DDG, 4.52 lb SBH; SBH, 6.87 lb SBH. b Standard error of the mean, n=56. c Plasma urea nitrogen. d, e, f, g Means with different superscripts within a row are different ( P <0.05).

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Table 3. Economics of supplementing dried distillers grains (DDG) or soybean hulls (SBH). Treatment a Item DDG DDG/SBH SBH/DDG SBH SEM b P value Supplement cost, $/ lb c 0. 091 0. 086 0. 082 0. 077 ----Feed cost, $/steer/d d 0.89 ef 0. 92 e 0.9 5 f 0. 87 f 0.0 1 0.07 Total feed, $/steer 37.4 3 ef 38.83 e 39. 91 f 36.53 f 2.53 0.07 Cost of gain, $/ lb BW gain/steer 0.590 e 0.499 f 0.554 ef 0.681 g 0.0 3 0.003 a Least square means; Treatment: DDG, 6.17 lb dried distillers grains; DDG/SBH, 4.25 lb DDG, 2.16 lb soybean hulls; SBH/DDG, 2.11 lb DDG, 4.52 lb SBH; SBH, 6.87 lb SBH. b Standard error of the mean, n=56. c Cost of supplements: $182/T DDG, $155/T SBH. d Cost of hay and supplement consumed per steer/d; hay cost, $30/bale. e, f, g Means with different superscripts within a row are different ( P <0.05).