Proceedings, Western Section, American Society of Animal Science
Vol. 54, 2003
EFFECTS OF FORAGE QUALITY AND TYPE OF PROTEIN SUPPLEMENT ON INTAKE AND
DIGESTIBILITY IN BEEF STEERS AND PERFORMANCE OF POSTPARTUM BEEF COWS
J. J. White, G. D. Pulsipher, and T. DelCurto
Eastern Oregon Agriculture Research Center, Union, OR 97883
ABSTRACT:
Two experiments were conducted to
evaluate the effects of forage quality and supplemental UIP
level on intake, digestibility, and performance of beef
cattle. In Exp. 1, five ruminally cannulated steers (BW =
456 + 6 kg) were used in a 6 x 5 incomplete Latin square
with treatments in a 2 x 2 factorial plus two controls.
Factors were hay quality, moderate (M, 8.0% CP, 62.1%
NDF) and low (L, 4.0% CP, 81.5% NDF), and supplement
type, high UIP (HUIP, 60% UIP, 48% CP) and low UIP
(LUIP, 40% UIP, 49% CP). Supplement was provided
daily to meet 100% of CP requirements. Intake and total
fecal output were measured on d 15 to 19, and total rumen
evacuations on d 21. Supplementation increased (P < 0.01)
DM intake and digestibility and NDF intake in steers fed L
forage. An interaction (P = 0.10) occurred for NDF intake.
In steers fed L forage NDF intake was greater with HUIP
supplement (2.6 kg/d) than with LUIP supplement (2.4
kg/d), but in steers fed M forage NDF intake was greater
with LUIP supplement (3.1 kg/d) than with HUIP
supplement (3.0 kg/d). Ruminal NDF fill and liquid
volume were greater (P < 0.07) in steers fed L forage
compared to M forage. In Exp. 2, 96 postpartum
multiparous cows (BW 555 + 8 kg) were blocked by
calving date and assigned to treatments in a 2 x 2 x 2
factorial arrangement within a split plot design. The
additional treatment factor in Exp. 2 was supplement intake
level, low or high 90 or 110% of CP requirements. Hay
quality was L (6.3% CP 75% NDF) and M (8.6% CP and
74% NDF). Supplements were fed three times weekly to
groups of four from calving to breeding. Cow BW and
BCS were taken at calving and breeding. Cyclicity was
determined prior to breeding and pregnancy was
determined at weaning. Cows receiving the high intake
level of supplement lost less (P = 0.06, -29 kg) BW than
cows on the low level (-33 kg). These results indicate that
quality of forage and protein supplement type interact to
affect intake, but not postpartum cow performance.
is the availability of low-cost, low-quality harvested
forages. However, these forages are often deficient in
protein (3.5% to 12.0% CP) but close to adequate in energy
(50% to 55% TDN). Therefore, when quantity is not
limiting, protein supplementation is the best way to increase
the value of these feeds. Since additional protein is
beneficial for cows consuming low-quality forages, the
issue then shifts to the type of protein that will elicit the
best results. The use of UIP in protein supplements has
been researched with inconclusive results. Pregnant beef
cows supplemented with UIP have experienced decreased
weight loss (Miner et al., 1990) while primiparous,
postpartum beef cows fed UIP have shown increased milk
protein (Hess et al., 1998), and weight gain (Sawyer, 2000;
Anderson et al., 2001). In contrast, Strauch et al. (2001)
found no effect on body weight or condition, reproductive
performance, or calf growth; and Sletmoen-Olson et al.
(2000) observed no response in body weight or
reproductive performance in response to increasing levels
of UIP supplementation. Steers supplemented with UIP
have demonstrated increased protein efficiency (Brown et
al., 1997) and gain (Zorrilla-Rios, 1991; McCann et al.
1991) in some studies, while showing lower gain (Ludden
et al., 1995) or variable response (Gutierrez-Ornelas et al.,
1991) in others. Undegradable intake protein has been
tested with basal diets ranging from low quality grass hay
(Alderton et al., 2000; Anderson et al., 2001) and dormant
pasture (McCann et al., 1991; Strauch et al., 2001) to high
quality grass pasture (Hongerholt, 1998). Protein levels
ranged from 4 to 25% CP, and in all but one of the
experiments (McMormick et al., 1999) the basal diets were
constant across treatments. The protein differences of the
basal diets may be an important contributing factor in the
variability of responses observed in cattle fed UIP. The
objectives of this study were to evaluate the interaction of
basal diet quality and supplement type on intake and
digestibility in beef steers and performance of postpartum
beef cows.
Keywords: forage quality, protein supplementation
Materials and Methods
Introduction
Cow-calf producers have a difficult time realizing a profit
in the beef industry. The greatest single expense for
cow/calf producers is providing feed, and the most
economical way to do this is through grazing. However,
ranchers in the Western United States are at a disadvantage
because of harsh environmental conditions and a lack of
pastureland, which limits them to as few as six months or
less of grazing. One advantage that western producers have
Two experiments were conducted at the Eastern Oregon
Agricultural Research Center in Union, OR to evaluate the
effects of forage quality and protein supplement type on
rumen digestibility and production. In Exp. 1 five
ruminally cannulated crossbred steers (BW = 456 + 6 kg)
were placed in individual pens and randomly assigned to
treatments in a 6x5 incomplete Latin square. Treatments
were arranged in a 2x2 factorial plus two controls. Factors
were basal diet, grass hay (M, 8.0% CP, 62.1% NDF) or
grass straw (L, 4.0% CP, 81.5% NDF) and supplement
type, high UIP (HUIP, 60% UIP, 48% CP) and low UIP
(LUIP, 40% UIP, 49% CP).
Supplements were
isonitrogenous and fed to provide the same amount of
protein on both the moderate and low forage diets.
Controls were an unsupplemented treatment of each hay
type.
Experimental periods were 21d in duration with d 1 to 14
for diet adaptation and d 15 to 21 for sample collection.
Steers were fed forage twice daily at approximately 0800
and 1600 hand supplement was given once a day at 0800 h
before the forage. Fresh water and trace mineral salt blocks
were always available. Samples of the forage were
collected from days 15 to 19. Orts were removed, weighed,
and sampled in the morning and steers were fed 120% of
the previous day’s consumed feed. Subsamples of the
forage, supplement, and orts were ground in a Wiley Mill
and analyzed for DM, OM, N (AOAC, 1990), and NDF
(ANKOM Technology Corporation Fairport, NY). Fecal
bags were placed on steers from d 15 to 19 and changed
twice daily at which time fecal weight was recorded and a
5% subsample was removed and frozen. At the end of each
period the feces were mixed, subsampled, dried and ground.
Later they were analyzed for DM, OM, N, and NDF.
On d 21 total ruminal evacuations were conducted just prior
(0 h) and 5 h after the morning feeding. Ruminal contents
were weighed, and volume was measured. Subsamples
were obtained dried at 50o C for 96 h and analyzed for DM,
OM, and NDF.
Data were analyzed using the GLM procedures of SAS
(1996) appropriate for a Latin square design. Means were
separated using orthogonal contrasts for a 2 x 2 factorial.
Results were considered significant at the P=0.10 level.
In Exp. 2, 96 postpartum multiparous cows (BW 555 + 8
kg) were stratified by calving date and assigned to one of
eight treatments (12 cows/treatment) in a 2x2x2 factorial
arrangement of treatments. Factors were basal diet quality,
supplement type, and supplement intake level. Basal diets
were two qualities of fescue grass straw; L (6.3% CP 75%
NDF) and M (8.6% CP and 74% NDF). Supplements were
isonitrogenous (approximately 46% CP) with two levels of
UIP, LUIP (40% UIP) and HUIP (60% UIP) fed at two
intake levels. Intake levels were based on basal diet quality
and expected intake so that animals received enough CP to
meet approximately 100% of CP and DIP requirements
NRC (1996) for the low intake level (LI) , or 120% of CP
and DIP requirements for the high intake level (HI) with the
LUIP supplement.
Sixteen cow/calf pairs were blocked by calving date and
placed in each of six pens. One basal diet was fed in each
pen (3 pens per basal diet). Cows were assigned to
treatments immediately following calving and placed in the
appropriate pen. Cows were fed supplement in groups of
four, three times per week. Therefore, each supplement
type and intake level was represented in each pen.
The
supplementation period was from calving until breeding.
Cows were weighed and body condition scored at calving
(initiation of supplementation), the mid point of the
supplementation period, and breeding (end of
supplementation). Calves were weighed at birth and the
end of the supplementation period. Two blood samples
were collected ten days apart from each cow just prior to
initiation of an estrous synchronization protocol and
analyzed for progesterone to determine cyclicity prior to
breeding. Pregnancy was determined at weaning by rectal
palpation. Forages and supplements were subsampled
weekly, composited, ground, and analyzed for DM, OM,
NDF, and N.
Data was analyzed as a split-plot within a randomized
complete block design using the MIXED procedure of SAS
(1996). The whole-plot experimental unit was pen and the
sub-plot experimental unit was supplementation groups
within pens. Cyclicity and pregnancy were analyzed using
the chi square procedure of SAS.
Results and Discussion
Forage and total intake and digestibility are presented in
Table 1. Steers on the L forage had a lower (P < 0.01)
forage and total DMI expressed as kg of intake or as a
percent of BW than steers on M forage. Supplementation
increased (P = 0.01) DMI in steers consuming L forage but
not in steers consuming M forage. For forage and total
DMI intake there was a tendency (P = 0.11) for an
interaction between forage quality and supplementation
types. On the L forage, DMI was greater with HUIP
supplement compared to LUIP (6.9 kg vs. 6.4 kg,
respectively), but on the M diet, LUIP resulted in the higher
intake (11.1 kg vs. 10.8 kg). Bohnert et al. (2002a) fed a
low-quality hay (5% CP) with three levels of UIP (none,
18% UIP, 60% UIP) and also observed no affect on forage
DMI but did find that supplementation increased total DMI,
regardless of type of supplement. In contrast to this,
Sriskandarajah et al. (1982) observed a greater increase in
forage DMI from UIP than from DIP in steers consuming
wheat straw. He also stated that when DIP requirements of
an animal are met, supplementation does not consistently
stimulate intake of low-quality roughages. We may have
seen an increase in DMI (forage and total) on the L forage
because of its very low quality but not with the M forage
because its protein content was adequate to meet protein
requirements of the rumen microbes.
Dry matter digestibility was greater (P < 0.01) for steers on
the M forage compared to the L forage. Coomer et al.
(1993) limit fed total mixed rations to Holstein steers with
different levels of UIP and found no difference in total tract
OM apparent digestibility and attributed his results to the
fact that with low UIP, more digestion occurs in the rumen
while with high UIP more digestion happens in the
intestine. In similar fashion, Petersen et al. (1985) while
feeding low-quality hay found no differences in rumen
OMD.
Intake of forage NDF was increased (P < 0.01) in the M
diet compared to the L diet (6.7 kg vs. 5.2 kg). There was
an interaction (P = 0.10) between forage and supplement
types for NDF intake. On the L forage, HUIP increased
NDF intake (5.6 kg vs. 5.2 kg) whereas on the M forage,
LUIP increased NDF intake (6.8 kg vs. 6.6 kg). As a
percentage of BW, NDF intake did respond to
supplementation and forage type.
Moderate forage
increased (P < 0.01) intake of NDF over L forage (1.5% vs.
1.1%) while supplementation increased (P < 0.01) NDF
intake only for the L forage (1.2% vs. 1.0%). There were
no differences (P > 0.10) in NDF digestibility
Total CP intake was increased (P < 0.10) by
supplementation on the L forage (0.47 kg vs. 0.21 kg) and
on the M forage (0.94 kg vs. 0.88 kg). Additionally, steers
on the L diet consumed less (P < 0.01) CP than steers on
the M diet (0.92 kg vs. 0.38 kg). Crude protein intake as a
percentage of BW was greater (P < 0.01) for the M forage
than the L forage (0.20% vs. 0.08%), and supplementation
increased (P < 0.01) CP intake for L forage compared to M
forage (0.10% vs. 0.04%). Crude protein digestibility was
greater (P = 0.07) for the M forage than L forage (56.8 vs
37.8%) while supplementation increased (P < 0.01) CP
digestibility for the L forage (49.3 vs. 14.9%), but had no
affect (P > 0.10) on the M forage.
Ruminal fill and volume are presented in Table 2. There
were no differences (P > 0.10) in DM fill, OM fill, or DM
or OM fill as a percentage of BW. The only factor
affecting NDF fill and NDF fill as a percentage of BW was
forage type. Ruminal NDF fill was greater (P < 0.01) for
the L forage than the M forage and NDF fill, as a
percentage of BW was also greater (P < 0.01) for the L
forage compared to the M forage. Liquid fill at both time 0
and 5 was only affected by forage type and was greater (P <
0.01) in L forage than M forage (64.5 L vs. 73.7 L and 74.3
L vs. 81.0 L for time 0 and 5 respectively). Rumen volume
was only different at t-0 where L forage had a larger (P =
0.07) volume than M forage (65.9 L vs. 68.0 L).
Cow BW and BCS and calf BW for Exp. 2 are shown in
Table 3. Initial BW was not different (P > 0.18) between
treatments. Body weight loss from calving to the mid-point
of the supplementation period, and end of the
supplementation period were decreased (P < 0.10) in cows
on the high supplement intake level compared to cows on
the low supplement intake level. Initial BCS was greater (P
< 0.07) in cows on the M forage compared to the L forage.
Body condition loss from calving to the mid-point of the
supplementation period was decreased (P < 0.01) in cows
on the high supplement intake level compared to the low
supplement intake level. A basal diet by supplement type,
basal diet by supplement intake level, and supplement type
by supplement intake level interaction (P < 0.10) was
detected for cow BCS change from calving to the end of
supplementatoin. Cow on the M forage and supplemented
with HUIP lost less body condition than cows
supplemented with LUIP, while cows fed L forage and
supplemented with HUIP lost more body condition than
cows supplemented with LUIP from calving to the end of
supplementation. On the M forage the high supplement
level decreased body condition loss more than on the L
forage. When HUIP supplement was fed increasing
supplemental intake decreased body condition loss, from
calving to the end of supplementation, more than when
LUIP supplement was fed.
Calf birth weight was not different (P > 0.10) among
treatments. An interaction (P < 0.02) of basal diet quality
and supplement type occurred for calf BW at the end of the
supplementation period. Calves from cows fed M forage
and supplemented with HUIP weighed less than calves
supplemented with LUIP, while calves from cows fed L
forage and supplemented with HUIP weighed more than
calves from cows supplemented with LUIP. A tendency (P
= 0.11) for an interaction between basal diet quality and
supplement type and basal diet quality and supplement
intake level occurred for calf ADG from birth to the end of
the supplementation period. Calves from cows fed M
forage and supplemented with HUIP gained less than calves
from cows supplemented with LUIP, while calves from
cows fed L forage and supplemented with HUIP gained
more than calves from cows supplemented with LUIP.
Calves from cows on the L forage had similar rates of gain
regardless of supplement level, however calves from cows
on the L forage supplemented at the high intake level had
higher rates of gain than calves from cows supplemented at
the low intake level. In general, treatments with a greater
loss in cow BCS had greater calf weight gain. This would
indicate that differences in milk production may have been
driving differences in cow performance. With HUIP
supplements potentially increasing milk production in cows
on L forage while LUIP supplements potentially increased
milk production in cows fed M forage. This agrees with
work done by Rusche et al. (1993) who showed that UIP
supplementation increases milk production in beef cows.
Cow cyclicity at the beginning of the breeding season was
unaffected by treatment (chi-square=.15). Similarly, cow
pregnancy rate at weaning was not affected by treatment
(chi-square=.70). Similarly, Sletmoen-Olson et al. (2000),
found that feeding protein supplements with equal levels of
CP and three levels of UIP reduced days to first estrus or
rebreeding. When supplementing isonitrogenous amounts
of protein differing in UIP content to late gestation cows,
Bohnert et al. (2002c) saw no affect of UIP cow
performance. In contrast, Triplett et al. (1995) observed
that in postpartum cows provided isonitrogenous protein
supplements at three levels of UIP, first-service conception
rates and pregnancy rates were reduced in the low UIP
treatment.
Implications
Forage quality affects the response of cattle to protein
supplementation.
Low quality forages respond to
supplementation with increases in intake and digestibility.
Our results indicate that UIP may be more advantageous
than DIP for steers on low-quality forage through increased
intake. However, in cows fed low-quality forage LUIP
supplements appear to be more beneficial while in cows
consuming moderate-quality forage HUIP supplements
appear to be more beneficial. An understanding of UIP
remains illusive and more research is needed in this area.
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Table 1: Intake and digestibility of nutrients in beef steers fed two qualities of forage and supplemented with two types (low UIP and high UIP) of protein supplement.
a
Treatment
Contrast, OSLb
c
Item
Mod. Control
Mod. HUIP Mod. LUIP
Low Control
Low HUIP
Low LUIP
SE
1
2
3
4
Forage DMI, kg
10.7
10.8
11.1
5.7
6.9
6.4
0.23
0.42
0.01
<0.01
0.58
Total DMI, kg
10.7
11.0
11.2
5.7
7.3
6.8
0.23
0.17
<0.01 <0.01
0.60
Total DMI, % BW
2.2
2.4
2.4
1.2
1.5
1.4
0.1
0.25
<0.01 <0.01
0.50
DM digestibility, %
60
60
60
52
54
54
1
0.96
0.24
<0.01
0.91
Forage NDF intake, kg
6.6
6.6
6.8
4.7
5.6
5.2
0.2
0.54
<0.01 <0.01
0.33
Total NDF intake, kg
6.6
6.7
6.8
4.7
5.7
5.2
0.2
0.46
<0.01 <0.01
0.33
Total NDF intake,
1.4
1.5
1.5
1.0
1.2
1.2
0.1
0.32
<0.01 <0.01
0.69
% BW
NDF digestibility, %
58
58
57
61
59
59
1
0.55
0.37
0.21
0.82
Forage CP intake, kg
0.88
0.86
0.87
0.21
0.26
0.22
0.04
0.86
0.53
<0.01
0.73
Total CP intake, kg
0.88
0.94
0.94
0.21
0.47
0.46
0.03
0.10
<0.01 <0.01
0.88
Total CP intake,
0.20
0.20
0.20
0.04
0.10
0.10
0.01
0.87
<0.01 <0.01
0.69
% BW
CP digestibility, %
56.5
56.7
57.1
14.9
48.0
50.4
0.1
0.94
<0.01
0.07
0.74
a
Treatments, Mod. = moderate hay quality, Low = low hay quality, HUIP = high UIP supplement, LUIP = low UIP supplement.
b
Contrast observed significance level, 1 = moderate hay control versus moderate hay supplemented, 2 = low hay control versus low hay supplemented, 3 = moderate hay
versus low hay, 4 = HUIP supplement versus LUIP supplement, and 5 = the interaction of hay quality and supplement type.
c
Standard error of the least square means (n= 5).
Table 2: Ruminal fill and volume in beef steers fed two qualities of forage and supplemented with two types (low UIP and high UIP) of protein supplement.
a
Treatment
Contrast, OSLb
c
Item
Mod. Control
Mod. HUIP Mod. LUIP
Low Control
Low HUIP
Low LUIP
SE
1
2
3
4
DM fill t-0d, kg
8.7
8.9
9.2
9.1
9.3
8.9
0.3
0.39
0.98
0.94
0.86
DM fill t-5d, kg
10.4
10.3
10.7
10.2
10.3
10.1
0.4
0.91
0.98
0.53
0.84
DM fill t-0d, % BW
1.9
2.0
2.0
2.0
2.0
2.0
0.1
0.35
0.94
0.90
0.84
DM fill t-5d, % BW
2.3
2.3
2.3
2.2
2.3
2.2
0.1
0.80
0.89
0.55
0.81
NDF fill t-0d, kg
5.7
5.9
6.0
7.0
6.9
6.6
0.3
0.4
0.52
<0.01
0.68
NDF fill t-5d, kg
6.9
6.7
7.0
7.9
7.6
7.4
0.4
0.89
0.36
0.07
0.89
NDF fill t-0d, % BW
1.2
1.3
1.3
1.5
1.5
1.5
0.1
0.39
0.54
<0.01
0.68
NDF fill t-5, % BW
1.5
1.5
1.5
1.7
1.7
1.6
0.1
0.98
0.43
0.08
0.84
Liquid fill t-0d, L
65.6
62.4
65.6
74.4
74
72.6
1.8
0.48
0.61
<0.01
0.63
Liquid fill t-5, L
73.8
73.3
75.7
80.2
81.7
81.2
1.9
0.76
0.61
<0.01
0.62
Total volume t-0d, L
68.3
62.1
67.2
66.4
68.0
69.6
2.1
0.17
0.36
0.07
0.13
Total volume t-5, L
78.6
77.0
77.9
72.6
74.4
76.5
2.09
0.66
0.28
0.05
0.17
a
Treatments, Mod. = moderate hay quality, Low = low hay quality, HUIP = high UIP supplement, LUIP = low UIP supplement.
b
Contrast observed significance level, 1 = moderate hay control versus moderate hay supplemented, 2 = low hay control versus low hay supplemented, 3 = moderate hay
versus low hay, 4 = HUIP supplement versus LUIP supplement, and 5 = the interaction of hay quality and supplement type.
c
Standard error of the least square means (n= 5).
d
Time in reference to the morning feeding, t-0 = just prior to the morning feeding and t-5 = five hours after the morning feeding.
5
0.11
0.11
0.14
0.79
0.10
0.10
0.23
0.83
0.51
0.79
1.00
0.81
5
0.33
0.54
0.49
0.71
0.38
0.41
0.58
0.55
0.23
0.48
0.42
0.64
Table 3: Cow BW, BW change, BCS, BCS change and calf birth weight and ADG in response to two qualities of basal forage supplemented with two types of protein
supplement (high UIP and low UIP) at two intake levels from calving to breeding.
Treatmentsa
Item
M-HUIP-HI
M-HUIP-LI
M-LUIP-HI
M-LUIP-LI
L-HUIP-HI
L-HUIP-LI
L-LUIP-HI
L-LUIP-LI
SEb
Initial cow BW, kg
550.1
548.5
557.1
563.3
585.9
527.8
541.7
568.5
23.6
Cow BW change
Initiaion to 3/19/02c,e
-22.9
-26.2
-30.7
-31.1
-15.7
-29.7
-21.5
-28.2
4.8
3/19/02 to 4/16/02c,e
-18.3
-24.9
-18.3
-32.7
-37.3
-33.8
-34.4
-42.9
4.3
Initiation to
-41.2
-51.0
-49.0
-63.7
-53.0
-63.4
-55.8
-71.1
5.7
4/16/02c,e,f
Initial cow BCSd
4.30
4.42
4.30
4.59
4.21
4.21
4.21
4.43
0.14
Cow BCS change
-0.6
-0.46
-0.19
-0.40
-0.27
-0.5
-0.21
-0.28
0.10
Initiation to
3/19/02c,e
3/19/02 to 4/16/02c
-0.36
-0.44
-0.40
-0.63
-0.38
-0.56
-0.59
-0.47
0.10
Initiation to
-0.42
-0.90
-0.59
-1.02
-0.65
-1.06
-0.79
-0.75
0.09
4/16/02c,g,h,i
Calf birth weight, kg
42.2
42.0
42.9
41.5
39.2
44.4
41.7
40.0
1.6
Calf BW 4/16/02, kgc,g
104.8
101.5
108.0
107.0
100.7
100.0
99.5
95.6
1.9
Calf ADG, kg/dd,e
0.93
0.89
0.95
0.97
0.90
0.82
0.88
0.81
0.02
a
Treatments: M = moderate-quality forage, L = low-quality forage, HUIP = high UIP supplement, LUIP = low UIP supplement, HI = high supplement intake level, and LI =
low supplement intake level.
b
Standard error of the least squares means (n = 3).
c
Initiation is at calving and the start of supplementation, 3/119/02 is the mid-point of the supplementation period, and 4/16/02 is the end of the supplementation period which
was just prior to breeding.
d,e,f,g,h,i
Means within a row were significant (P < 0.10) for the following effects; d = basal diet quality, e = supplement intake level, f = supplement type, g = the interaction of
basal diet quality and supplement type, h = the interaction of basal diet quality and supplement intake level, and i = the interaction of supplement type and supplement intake
level.