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- Title
Effects of energy supplementation on leucine utilization by growing steers.
- Authors
Schroeder, G. F.; Titgemeyer, E. C.; Moore, E. S.
- Abstract
The effects of energy supplementation on leucine (Leu) utilization in growing steers were evaluated using 6 ruminally cannulated Holstein steers (initial BW = 150 ± 7 kg) in a 6 × 6 Latin square design. All steers were limit-fed (2.3 kg/d of DM) a diet based on soybean hulls and received a basal ruminal infusion of 100 g/d of acetate, 75 g/d of propionate, and 75 g/d of butyrate, as well as abomasal infusions of 200 g/d of glucose and a mixture (215 g/d) containing all essential AA except Leu. Treatments were arranged as a 3 × 2 factorial with three amounts of Leu infused abomasally (0, 4, and 8 g/d) and supplementation with two amounts of energy (0 and 1.9 Mcal/d of GE). The supplemental energy was supplied through ruminal infusion of 100 g/d of acetate, 75 g/d of propionate, and 75 g/d of butyrate, as well as abomasal infusion of 200 g/d of glucose to provide energy to the animal without affecting microbial protein supply. Total tract apparent DM digestibility (71%) and fecal N excretion (17 g/d) were not affected by the treatments. Nitrogen balance was increased linearly (P < 0.01) by abomasal supplementation of Leu as a result of linear (P < 0.01) decreases in urinary N excretion, which demonstrated that, as designed, Leu was the limiting AA. Energy supplementation increased N balance (P < 0.01) as a result of decreased urinary N excretion (P < 0.01), indicating that energy supplementation improved the efficiency of Leu utilization. When additional energy was supplied, N retention increased linearly in response to Leu (25.6, 28.5, and 31.6 g/d for 0, 4, and 8 g/d of Leu). However, when no energy was supplemented, increases in N retention were similar for 4 and 8 g/d of Leu (24.5, 27.0, and 27.3 g/d for 0, 4, and 8 g/d of Leu). The efficiency of supplemental Leu utilization was 0.31. Energy supplementation appeared to improve Leu utilization by modestly increasing N retention when Leu was limiting (0 or 4 g/d of supplemental Leu) and by increasing the ability of steers to respond to the highest amount of supplemental Leu (8 g/d).
- Subjects
BOARD of Governors of the Federal Reserve System (U.S.); LEUCINE; BEEF cattle; MAGIC squares; RICE hulls; POWER resources; EXCRETION; BUTYRATES
- Publication
Journal of Animal Science, 2006, Vol 84, p456
- ISSN
0021-8812
- Publication type
Article