Effect of glycine and vitamin supplementation on sulphur amino acid utilization by growing cattle

Abstract

Effects of glycine (Gly) and B-vitamins on sulphur amino acid (AA) utilization were studied in growing steers maintained under conditions where methionine (Met) was first limiting. Conditions were generated by limit feeding a diet low in ruminally non-degraded protein and abomasally infusing an AA mixture limiting in Met. Retained N tended (p = 0.07) to improve when steers received 10 mg folate, 10 mg vitamin B6, and 0.10 mg vitamin B12 daily. Hepatic vitamin B12 (p = 0.08) and folate (p = 0.05) concentrations increased with vitamin supplementation. In another trial, factorial treatments were 2 or 5 g/day L-Met and 0 or 50 g/day Gly infused abomasally. Retained N increased (p < 0.05) in response to Met, and responses were numerically larger in the presence of supplemental Gly. In a different trial, factorial treatments were 0 or 2.4 g/day L-cysteine (Cys) and 0 or 40 g/day Gly. Retained N was not affected by Cys in the absence of Gly, but was increased by Cys when Gly was supplemented (interaction, p = 0.01). B-vitamin status may affect sparing of Met by Cys. Supplemental Gly improved responses to supplemental Met and Cys.

Ruminal ammonia load affects leucine utilization by growing steers1

“…The pH of the infusate was 5.5. PyridoxineؒHCl (10 mg/d), folic acid (10 mg/d), and cyanocobalamin (100 g/d) were added to the mixture because Lambert et al (2004) demonstrated that steers maintained under our experimental conditions were deficient in one or more of these vitamins. Leucine was dissolved separately and added to the mixture according to treatment (0, 4, or 8 g/d).…”

Efficiency of lysine utilization by growing steers1,2

“…After all AA were dissolved, the 2 solutions of AA were mixed together, dextrose was added (330 g supplying 300 g glucose) to provide an additional energy source, and water was added to bring the total weight of the daily infusate to 4 kg. All steers received 10 mg of pyridoxine·HCl/d, 10 mg of folic acid/d, and 100 μg of cyanocobalamin/d in the abomasal infusate because the experimental diet was deficient in at least one of those vitamins (Lambert et al, 2004). To ensure adequate ruminal ammonia concentrations to support microbial growth, all steers received a ruminal infusion of 10 g of urea/d; this was considered part of the dietary N intake.…”

Effect of ruminal ammonia supply on lysine utilization by growing steers1

“…The 3 solutions (AA/dextrose mixture, Glu, and Lys) were mixed together in individual bottles and water was added to bring the daily abomasal infusate weight to 4 kg. Pyridoxine HCl (10 mg/d), folic acid (10 mg/d), and cyanocobalamin (0.1 mg/d) were dissolved and added to the abomasal infusate because steers under these experimental conditions may become deficient in at least one of those vitamins (Lambert et al, 2004).…”