EFFECTS OF BETA-HYDROXY-BETA-METHYL BUTYRATE ON PERFORMANCE AND CARCASS QUALITY OF FEEDLOT STEERS

Beta-hydroxy-beta-methyl butyrate (HMB), a compound formed during cata bolism of leucine, was fed to 256 crossbred steers as 0 or .03% of die t dry matter. Effects on performance, carcass characteristics, and tis sue composition were measured. Groups of 32 steers per diet were slaug htered after 105, 119, 133, and 147 d on feed. The HMB was fed on each group only during the final 82 d they were fed. Averaged across slaug hter date, animal performance was not altered by HMB; however, an inte raction between HMB and time on feed was detected. Feeding HMB increas ed (P < .01) daily gain of steers slaughtered at 105 d but decreased ( P < .01) daily gain of steers slaughtered at 147 d. Steers fed HMB had numerically higher marbling scores that resulted in a trend toward hi gher carcass quality grades. Steers receiving HMB tended to have less (P < .08) s.c. fat and fewer steers with yield grades of 4 or greater (1.6 vs 4.7%). Supplementation of HMB to feedlot steers tended to incr ease (P < .07) the ratio of intramuscular fat to subcutaneous fat. Ste ers fed HMB had higher (P < .001) blood plasma concentration of HMB (3 .06 vs 1.70 mg/L) and lower (P < .03) blood plasma concentrations of c holesterol (108.4 vs 118.7 mg/dL). Feeding HMB tended to increase (P < .10) lipid content of the longissimus muscles of those steers slaught ered at 105 d.