341 Effects of Supplemental Betaine on Protein Deposition and Plasma Amino Acid Concentrations in Growing Steers with Modulated Methyl Group Status

Abstract Methyl group donors (e.g., methionine, betaine) may improve performance of growing beef cattle. Our objective was to evaluate effects betaine supplementation on protein deposition and plasma amino acids in steers with altered methyl status. Seven ruminally cannulated Holstein (189 kg) were used a 6×6 Latin square design 10-d periods. Factorial treatments continuously infused abomasally included 3 modulators [MGM; control; 15 g/d guanidinoacetic acid (GAA); or 16.8 creatine] 2 levels (0 5.7 betaine). Supplemental GAA creatine increases body supply; however, consumes groups during synthesis, whereas spares by reducing synthesis. Steers received 3.5 kg/d (DM basis) corn-based diet. Total collection urine feces occurred d 7 through 9 measure N retention. Jugular blood collected 10. No interactions between MGM observed (P≥0.17). Betaine increased retained (P=0.03), but did not affect urinary fecal excretion (P≥0.16). Met (P=0.03) cystine (P=0.04) tended decrease Lys (P=0.10). Nitrogen retention affected (P=0.63). Creatine (P=0.04), increase (P=0.08). relative control (P=0.02); also (P< 0.01). Plasma (P=0.41). decreased (P=0.01), (P=0.26). 0.01) (P=0.05) control. improved altering status concentrations.