Level of rumen undegradable protein (RUP) in high-grain diets fed to feedlot lambs
J.J. Reed, M.L. Bauer, G.P. Lardy,
P.T. Berg.
Introduction
Rumen undegradable protein (RUP) is
protein that bypasses the rumen. Rumen undegradable protein flows to the small
intestine where digestion takes place. Rumen degradable protein (RDP) is
protein that is broken down by ruminal microorganisms. Loe et al. (2000)
evaluated the addition of RDP and RUP to corn-based lamb finishing diets.
Treatments with added RUP contained 7.3% RUP. Lambs fed additional RUP had
heavier final weights, gained more rapidly, and were more efficient compared
with RDP fed lambs. Loe et al. (2001) conducted research to determine the
optimum level of RDP in lamb finishing diets. Feeding levels between 6.1 and
11.0% RDP did not affect gain or feed efficiency. They concluded that the
optimal level of RDP does not appear to be above 6.1% in lambs with the ability
to gain at least 1.06 lb/day. Little research has been conducted on RUP in lamb
finishing diets. The objective of this study was to determine the optimum level
of RUP in lamb finishing diets.
Materials and Methods
Seventy-four
crossbred ram lambs (85.4 ± .83 lb initial weight) were fed for 74 d days to
determine the optimal level of RUP in corn-based finishing lamb diets. Lambs
were housed at the NDSU Animal Research Center barns. The lambs were blocked by
weight and allotted randomly to dietary treatments (5 pens/treatment). Each pen
had access to an outdoor and indoor run and fresh water.
Diets consisted of corn, beet pulp pellets,
molasses, soybean meal, urea, feathermeal, bloodmeal, and supplement (Table 1).
Diets were offered ad libitum once daily. Treatments contained 6, 7, 8, or 9%
RUP (dry matter basis). Rumen undegradable protein sources were feathermeal and
bloodmeal combinations. Level of RDP was held constant at 6.9% in all
treatments.
Three day weights were taken at the
beginning and end of the trial to measure average daily gain. Unconsumed feed
was removed from the bunks and weighed weekly to measure dry matter intake.
Carcass data was collected at slaughter. Hot carcass weight, fat thickness,
rib-eye area, bodywall thickness, marbling, flank streaking, leg score, and
conformation score were taken.
Results
No treatment affects on performance
occurred (Table 2). Rib-eye area increased linearly (P = 0.06) with increasing
level of RUP. There were no other affects on carcass characteristics (Table 3)
with respect to treatment.
Conclusions
Lack of treatment effects may indicate that lambs on finishing diets do not need more than 6% RUP. However, a previous study indicates improved performance with lambs fed 7.3% RUP versus 5.9%.
The lack of treatment effects in
this study may be due to poor lamb performance. In this study, lambs gained
only 0.66 lb/day. In a previous study (Loe et al., 2000), lambs fed RUP at 7.3%
gained .87 lb/day. In another study (Loe et al., 2001), lambs fed 7.3% RUP with
varying levels of RDP gained 1.07 lb/day.
|
Table 1. Formulated dietary treatments (%, DM Basis) |
||||
|
|
Level of rumen undegradable protein, (%, DM Basis) |
|||
|
Item |
6 |
7 |
8 |
9 |
|
Corn |
75.43 |
74.28 |
73.13 |
71.99 |
|
Beet pulp pellets |
12.50 |
12.50 |
12.50 |
12.50 |
|
Molasses |
5.00 |
5.00 |
5.00 |
5.00 |
|
SBM |
1.99 |
1.33 |
0.66 |
0.00 |
|
Urea |
0.22 |
0.15 |
0.07 |
0.00 |
|
Feathermeal |
1.51 |
3.02 |
4.53 |
6.04 |
|
Bloodmeal |
0.38 |
0.76 |
1.13 |
1.51 |
|
Supplement |
2.97 |
2.97 |
2.97 |
2.97 |
|
Protein |
|
|
|
|
|
Crude |
12.90 |
13.90 |
14.90 |
15.90 |
|
Rumen degradable |
6.90 |
6.90 |
6.90 |
6.90 |
|
Rumen undegradable |
6.00 |
7.00 |
8.00 |
9.00 |
|
Metabolizable |
7.66 |
8.47 |
9.28 |
10.08 |
|
Table 2. Effect of treatment on performance |
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|
|
Level of rumen undegradable protein, (%, DM Basis) |
||||
|
Item |
6 |
7 |
8 |
9 |
Standard Error |
|
Weight, lb |
|
|
|
|
|
|
Initial |
85.3 |
84.7 |
86.1 |
85.5 |
0.8 |
|
Final |
131.3 |
134.3 |
136.7 |
134.8 |
2.5 |
|
Dry Matter Intake |
|
|
|
|
|
|
lb/day |
3.01 |
3.08 |
3.30 |
3.19 |
0.10 |
|
% of body weight |
2.80 |
2.82 |
2.99 |
2.90 |
0.08 |
|
Average daily gain, lb |
|
|
|
|
|
|
live wt basis |
0.62 |
0.67 |
0.68 |
0.67 |
0.04 |
|
carcass basisa |
0.65 |
0.68 |
0.67 |
0.68 |
0.04 |
|
Gain: Feed |
0.206 |
0.217 |
0.206 |
0.210 |
0.007 |
|
Feed: Gain |
4.85 |
4.60 |
4.85 |
4.76 |
--- |
a Based on hot carcass
weight and 50% dress
|
Table 3. Effect of treatment on carcass characteristics |
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|
|
Level of rumen undegradable protein, (DM Basis) |
||||
|
Item |
6 |
7 |
8 |
9 |
Standard Error |
|
Hot carcass weight, lb |
66.55 |
67.49 |
68.01 |
67.90 |
1.42 |
|
Fat thickness, in |
0.17 |
0.17 |
0.17 |
0.19 |
0.02 |
|
Rib-eye area, in2a |
2.35 |
2.49 |
2.49 |
2.53 |
0.06 |
|
Bodywall thickness, in |
0.91 |
0.93 |
0.86 |
0.90 |
0.04 |
|
Marbling |
375 |
389 |
377 |
359 |
17 |
|
Flank streaking |
369 |
339 |
350 |
337 |
14 |
|
Yield grade |
2.08 |
2.12 |
2.12 |
2.30 |
0.18 |
|
Leg score |
11.12 |
11.20 |
11.50 |
11.22 |
0.21 |
|
Conformation score |
11.07 |
11.20 |
11.25 |
11.22 |
0.22 |
a Linear response to treatment (P = 0.06)
b Marbling score of 300 = slight
c Score of 11 = low choice