Energy and protein supplementation of ammoniated wheat straw diets for growing steers.

Abstract

Eighty-eight yearling beef steers (308 +/- 1.4 kg) were used in two separate trials to determine the protein-sparing value of the N added to wheat straw during the ammoniation process and to determine the effects of supplementing ammoniated straw diets with energy and ruminal escape protein. In Exp. 1, steers were fed untreated straw (US) with either 0, 150, or 500 g of soybean meal (SBM) for 88 d. The addition of SBM to US diets increased (P less than .01) straw intake and average daily gains (ADG), indicating that N was limiting. When ammoniated straw (AS) was substituted for US, the N in the AS was used as efficiently as 500 g of SBM for growth. In Exp. 2, steers had ad libitum access to AS with three levels of supplemental corn (0, 1.23, or 2.45 kg DM.animal-1.d-1) either with or without .41 kg DM of corn gluten meal (CGM) added. Straw intake decreased (P less than .01) as the amount of corn in the diet was increased, but ADG increased (P less than .01) with the addition of corn. Straw consumption was not altered by the addition of CGM, but ADG was increased (P less than .01) by an average .35 kg by CGM. Rumen and blood N components indicated that the N from AS was contributing to the ruminal N pool and that CGM was compensating for microbial protein deficiencies postruminally.

Full text

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J. Zorrilla-Rios, G. W. Horn, W. A. Phillips and R. W. McNew
steers
Energy and protein supplementation of ammoniated wheat straw diets for growing
1991, 69:1809-1819.
J ANIM SCI
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ENERGY AND PROTEIN SUPPLEMENTATION
OF AMMONIATED WHEAT STRAW DIETS
FOR GROWING STEERS'
J. zorrilla-Rios2, G. W. Horn3, W. A. Phillip8 and R. W. McNew5
Oklahoma Agricultural Experiment Station, Stillwater 74078-0425 and
U.S. Department of Agriculture, Agricultural Research Service,
El Reno, OK 73036
ABSTRACT
Eighty-eight yearling beef steers (308 f 1.4 kg) were used in two separate trials to
determine the protein-sparing value of the N added to wheat straw during the ammoniation
process and to determine the effects of supplementing ammoniated straw diets with energy
and ruminal escape protein. In Ekp. 1, steers were fed untreated straw (US) with either 0,
150, or 500 g of soybean meal (SBM) for 88 d . The addition of SBM to US diets increased
(P e .01) straw intake and average daily gains (ADG), indicating that N was limiting.
When ammoniated straw (AS) was substituted for US, the N in the AS was used as
efficiently as 500 g of SBM for growth. In Exp. 2, steers had ad libitum access to AS with
three levels of supplemental corn (0, 1.23, or 2.45 kg DM~a~~imal-~.d-~)
without .41 kg DM of corn gluten m e a l ( E M ) added. Straw intake decreased (P e .01) as
the amount of corn in the diet was increased, but ADG increased (P e .01) with the
addition of corn. Straw consumption was not altered by the addition of CGM, but ADG
was increased (P < .01) by an average .35 kg by CGM. Rumen and blood N components
indicated that the N from AS was contributing to the ruminal N pool and that CGM was
compensating for microbial protein deficiencies postnuninally.
Key Words: Ammoniated Feeds, Wheat Straw, Supplementation, Protein Utilization
either with or
J. Anim. Sci. 1991. 69:1809-1819
Introduction
Chemical treatments of lowquality rough-
ages such as wheat straw that increase feed
intake and energy digestibility by ruminants
lJoumal Article 5771 of the Agric. Exp. S t a .
Oklahoma State Univ., Stillwater. Supported by ARS
C y t i v e Agreement #8-7B30-9-87.
Postdoctoral R e s . Assoc. on leave f r o m Institute
Nacional de Iwestigaciones PecuariaS, Secretaria de
Agridtura y Recafios Himaalicos, Mexico. Resent
Address: Beef Cattle Branch, W e s t e r n Anstralia, Dept. of
Agric.. Bunbury.
3~nim. Sci ~ e p t
bporaBe and Livest. R~S. w.,
1199, El Reno, OK 73036.
'Present Address: Agric. Stat. Lab., 116D Agric.
Bldg., Univ. of Axkauw, Fayetteville 72701.
Received June 11, 1990.
Accepted October 24, 1990.
USDA-ARS, P.O. BOX
(Al-Rabbat and Heany, 1978; Horton and
Steacy, 1979) can increase the need for
nutrients by both ruminal bacterial and the host
animal. Nitrogen added to wheat straw during
ammoniation presumably can decrease the
need for supplemental N. The objective of
Exp. 1 was to determine the nutritive value of
the N added to wheat straw during ammonia-
tion
The ruminant is dependent on microbial
protein synthesis to convert N fium am-
moniated roughages to usable amino acids.
When microbial synthesis is limited, supple-
mentation with ruminal escape protein is
appropriate and beneficial (ARC, 1980; Egan,
1981; NRC, 1985). The objective of Exp. 2
w a s to determine the effect o f supplemental
ruminal escape protein (corn gluten meal) and
of merent amounts of energy (corn) on
growth rate of beef steers fed ammoniated
wheat straw diets.
1809
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1810
ZDRRIL.LA-RIOS ET AL.
Materlals and Methods
Experiment I. Wheat straw (Triumph 64)
was harvested in large round bales shortly after
the grain had been harvested, it was stored
outside for 3 mo before being ammoniated by
the stack method (Sunstol e t al., 1978). The
straw was ammoniated in two separate stacks
with 44 and 33 g of NH&g of DM, it
remained covered and was left undisturbed for
23 and 17 d, respectively, after ammoniation.
Untreated straw (US) was stored under cover
during the ammoniation period. Both the US
and ammoniated straw (AS) were ground to a
particle length of approximately 2.5 cm before
feeding.
Thiay-two Beefmaster x Hereford-Angus
s t e e r s (288 f 3.1 kg) were blocked according
to weight and, within block, were assigned
randomly to individual pens and to one of four
treatments. For the &t t h r e e treatments each
steer had ad libitum access to US supple
mented with 0,150, or 500 g of soybean meal
(SBM) DM and 2.32, 2.20, or 1.86 kg of corn
DM to meet net energy requirements for .45 kg
daily live weight gain. For the fourth treat-
ment, each steer was limit-fed AS, no SBM
and 2.35 kg of corn DM once daily. The
amount of AS offered in Treatment 4 was
restricted to the weekly average of that
observed for the group fed US + 500 g o f
SBM. Steers of all treatments also were fed
.711 kg of DM/d of a corn-based mineral and
vitamin supplement (Table 1) to meet quire
ments for Ca, P, S, Mg, K, and vitamins A, D,
and E (NRC, 1984). Straw and supplements
were fed once daily in separate containers.
Orts were measured on a weekly basis and
discarded during the 88d trial. Initial and final
body weights were measured after
16-h shrink; a maintenance level of alfalfa hay
was fed for 5 d before the final weight was
taken on d 93 to decrease differences in gut
fiu.
Blood and ruminal samples were taken at 2
h after feeding on d 57,4 h after feeding on d
64, and 8 h after feeding on d 79. Blood
samples were collected in tubes containjng
EDTA and kept on ice until the plasma could
be harvested by centrifugation. The plasma
w a s frozen u n t i l it was analyzed for t o t a l
protein by the biuret method (Sigma Chemical
Co., 1980) and urea N by the urea-diacetyl
a
TABLE 1. DRY MAlTJ3R, OM, 8
CONTENT, AND IN VITRO DRY MATI'ER DIGESTJBIU'IY ( r v D m )
AM) CALCULATED "T
CONTENT OF DIETS W. 1)
Feedstuffs
m e a t straw
Untreatad
Stack 1
Stack 2
Ammoniatd
87.4
78.3
Stack 1
Stack 2
Ground corn
soybean meal
Mioeral and vitamin m p p l d
7 1 . 5
70.2
87.2
8 7 . 9
89.4
OM
CP
mm
96 DM
94.3
94.2
3.4
3 . 8
30.5
215
9 3 . 1
9 4 5
98 A
92.7
78.4
7.4
7.4
1 0 . 9
4 9 . 5
9 . 0
45.7
3 3 . 9
-
-
-
nLle of straw and treatmentsb
us
AS
Nuhient contwt of diets
NE, hacallkgDM (calc)c
NEg,McavkgDM(calc)c
CP, I
ofDM (analyzed)
%nerd and vitnmin suppluuent composition (grams/kilogram of DM): ground corn, 778.6; &calcium phcsphate,
97.1; potapsh date, 57.1; magnesium oxide, 1 4 . 3 ; trace mineralized salt, 3 5 . 7 (grams/ldogm~ salt, 945; manganese,
25; h
A, 1.764 X 106 W,
vitamin D, 176 X I d I Q vitamin E, 7,500 I U ) .
% of straw: untreated (US); ammoniated (AS). SBM = soybean meal supplement; 0, 150, and 500 g DM.
tlnimar 4-1.
0 SBM
1 . 3 9
. 7 7
6.76
150 gld SBM
1 . 3 8
. 7 5
7.62
500 gld SBM
1 . 3 5
.73
9.64
0 SBM
1.36
. 7 3
9.57
2.9 sulfur, .3; copper, .33 cub&, .m; iodine, .07; and zinc, .M);
vitamin premix, 1 7 . 1 @er kilograms:vitamin
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AMMONIATED WHEAT STRAW FOR GROWING STEERS
1811
monoxime method (Sigma Chemical Co.,
1983). Ruminal fluid was collected via stom-
ach tube equipped with a metal Strainer. The
pH of the ruminal fluid was determined using
a pH electrode. Ten milliliters of ruminal fluid
was added to 2 ml of 25% metaphosphoric
acid; this mixture was frozen u n t i l it was
analyzed for total and individual fatty acids by
gas chromatography. Concentrated sulfuric
acid (1 ml) was
50-ml ruminal subsample; this mixture was
frozen u n t i l ammonia (NH3 N) concentration
was determined by MgO distillation (AOAC,
1975).
Weekly feed samples and orts were ana-
lyzed for DM (55°C' 48 h), ash (500'C, 5 h),
and total N (macro-Kjedahl, AOAC, 1975). In
vitro dry matter digestibility (IVDMD) of US
and AS was determined according to the
procedure of Tilley and Terry (1963). but the
buffer described by McDougall (1948) was
modified to contain only one-tenth the speci-
fied concentration of CaCl2 and 1 g of urea/
liter of buffer was added.
Data were analyzed by least squares
ANOVA. The model used to compare treat-
ment differences in nutrient intake and body
weight changes included effects of block, type
of straw, levels of SBM supplementation, and
the interaction of straw type x SBM supple-
mentation. The variation among SBM levels
was partitioned into linear and quadratic terms.
Ruminal fluid and blood parameters within and
across all hours of sampling were analyzed
using two different models. For the within-
hour analysis, the model included block and
treatment effects, whereas for the among-hours
analysis, the model included block, treatment,
and hour, as well as the interactions block x
treatment, block x hour, and hour x treatment.
Treatment effect for this second model was
tested using block x treatment as the error
term. In the last two analyses, Duncan's
Multiple Range procedure was used to com-
pare treatment means.
Experiment 2. Wheat straw, ammoniated by
the stack method using 43 g of MI3 Nkg of
DM, was ground to approximately 2.5 cm
lengths and stored u n t i l fed. F i f t y - s i x Charolais
x Hereford-Angus steers (3 18 f 1.9 kg) were
blocked by weight and within block were
assigned randomly to individual pens and one
of seven treatments. The six AS diets were in a
3 x 2 factorial arrangement of treatments with
three daily intakes (0, 1.23, or 2.45 kg DM) of
corn plus two levels (0 and .41 kg DM) of corn
gluten meal (CGM). A seventh treatment was
added to another
US supplemented daily with 1.23 kg of DM
from corn plus .41 kg DM of CGM. A l l steers
received .669 kg DM.ani~nal-'&~ of a com-
based mineral and vitamin supplement to meet
the daily requirements (NRC, 1984) for Ca, P,
S, Mg, K, and vitamins A, D, and E. Wheat
straw was available ad libitum, whereas the
other dietary ingredients were mixed together
and fed once daily separate from the straw.
Orts were measured each week for the
77-d trial, and B W was measured as described
in Exp. 1. The collection and analysis of the
feed samples, refusals, ruminal fluid, and
blood were the same as in Exp. 1. However,
only 35 steers were used for blood and ruminal
sampling and all samples were collected on d
77.
Data were analyzed by least squares
ANOVA. Rumen and blood measurements
were analyzed by hour and across all hours as
described in Exp. 1. A randomized block
analysis was used to determine differences in
BW changes and nutrient intakes with or-
thogonal comparisons to determine the effects
o f ammoniation, CGM supplementation, and
corn supplementation (linear and quadratic
responses) as well as the interactions between
CGM and the linear and quadratic effects of
corn supplementation.
Results and Discussion
Experiment 1. Chemical composition of the
feedstuffs and calculated nutrient content of
the diets used in Exp. 1 are shown in Table 1.
The IVDMD of US of Stack 2 was inexplica-
bly low, WDMD of both stacks of straw was
increased approximately 54% by ammoniation.
Ammoniation almost doubled the CP content
of both stacks of straw. Retention of ammonia
N was 18 and 21% by Stacks 1 and 2,
respectively. Previously reported values for
retention of ammonia N by wheat straw have
been 25 and 15% (Nelson et al., 1985; Trials 1
and 2, respectively), 26% (Zorrilla-Rios et al.,
1985a), and 49% (Saenger et al., 1983). In the
study of Saenger et al. (1983), wheat straw
was ammoniated in a covered concrete bunker
silo rather than i n the open. The DM content of
AS at feeding was decreased by ammoniation
from 87.4 to 71.5% (Stack 1) and from 78.3 to
70.2% (Stack 2). This decrease in DM content
of AS was due to increased weathering (i.e.,
penetration of rain) of the bales after the stacks
were uncovered. Straw composed 52% of the
diet; mean daily DM intake of the diets was
2.1% of BW (Table 2). Intake of US increased
linearly (P c .01) as SBM replaced corn grain
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1812
ZORRLLA-RIOS ET AL.
in the supplement; daily gains increased (P e
.01) quadratically as SBM replaced corn in the
supplement f o r US. Responses in straw intake
and gain have been attributed to correction of
the N deficiency in the rumen (Balch, 1967;
Horn et al., 1981; Pace et a l . , 1982). A similar
response was reported by Saenger et al. (1982)
with corn stover. Although steers fed AS
consumed only 10.4% more straw than steers
fed US without SBM added, they gained more
rapidly (P e .01) and had daily gains similar to
those of steers fed US plus 500 g of SBM/d.
Therefore, substitution of AS for US elimi-
nated the need for the additional SBM and
demonstrated that the N added to the wheat
straw during the ammoniation process could
meet requirements of ruminal bacteria for
synthesis of microbial protein for this level of
steer performance.
Ruminal NH3 N concentration increased (P
e .05) as SBM replaced corn in the supplement
(Table 3). Steers consuming AS had ruminal
NH3 N concentrations intermediate to those
observed for the two US groups with SBM
added. Ruminal pH was not altered by the
level of SBM supplementation or ammonia-
tion; it was typical for high-forage diets (Lyle
et al., 1981). Plasma protein concentration was
not affected (P > .IO) by level of SBM
addition or the addition of AS. However,
plasma urea N increased (P e .05) as SBM
replaced corn in the supplement and paralleled
CP intake with US diets. Although replace-
ment o f US by AS and deletion of the SBM
did not decrease, total N intake compared with
steers receiving 500 g of SBM (Table 2), it did
decrease (P e .05) plasma urea N concentra-
tion (17.09 vs 7.77 mg/dl). This may reflect a
more sustained or decreased rate of N release
from AS. Replacement of corn by SBM in the
supplement linearly increased (P < .05) total
VFA concentration and increased the molar
proportions of branched-chain fatty acids
(BCFA) in ruminal fluid. Steers fed AS had
lower (P e .05) total VFA and BCFA
concentrations but higher acetate proportions
than those fed US plus 500 gld of SBM (Table
3). Because ADG increased linearly with in-
creasing amounts of N from SBM, US diets
presumably were deficient in N. Although AS
intake was limited to that observed for US plus
the highest level of SBM in the diet, digestible
OM intake presumably was greater, so sites of
TABLE 2. LEAST SQUARES MEANS OF INTAKE OF FEEDSTUFFS AND " T S ,
BODY WEIGHT CHANGES AND AVERAGE WEIGHT GAIN OF STEERS (EXP. 1; N = 8)
Sources o f variation
and probability levelb
Type of strawa
us
150g/d
SBM
SBM
us
vs
ASc
AS
500gfd
SBM
Item
T o t a l D d
W d
%BW
S t r a w DM
W d
% total DM
Corn, kg DM/d
CP, W d
Body wt, kg
Initial
Final
Wemt gain, kg/d
ME value of stm@
Mcallkg DM
% of NRC, 1984
&L'reatmenls: US = unheated wheat straw; AS = ammoniated wheat s t r a w SBM = soybean meal; supplement: 0.150,
and 500 g ~ ~ . a n i m a l - W .
OSBW
0 SBM SE
Lin
Quad
6.32
2.09
326
51.6
2.32
. 4 4
288
3 14
.278
1.01
68
6.59
2.15
3.48
52.8
2.20
50
288
323
.378
1.21
81
6.72
2.17
3.63
54.0
1.86
.64
289
332
.460
1.40
95
6.68
2.15
3.60
53.9
2.35
.65
287
331
. 4 8 0
1.41
96
.06
.M
.06
.57
.M
.05
.38
.66
.007
*
NS
**
**
**
**
**
**
**
**
**
NS
**
**
NS
**
**
NS
NS
NS
NS
NS
NS
*
**
**
h v e l of significance, NS = not significant; *P < ,05, **P < .01; Lin = linear effect and Quad = quadratic effect of
SBM within US treatments.
'AS vs US + 0 SBM.
dD.y matter (DM), includes .711 kg of a com-based mineral and vitamin supplement.
%timated from cattle performance data according to Hays et aL (1987).
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