INFLUENCE OF SUPPLEMENTAL TRYPTOPHAN AND ZERANOL IMPLANTATION ON PERFORMANCE, CARCASS COMPOSITION, SERUM HORMONES AND NUTRIENT UTILIZATION BY LAMBS

In Expt. 1, treatments were two levels zeranol (0, 12 mg implant) and three levels tryptophan (TRP: 0, 0.5, and 1% DM of diet) in a factoria l design. Tryptophan and zeranol interacted (P<0.05), such that lambs receiving 0.5% TRP only and lambs receiving 1% TRP plus zeranol had gr eater (P<0.05) OM intakes than did lambs receiving 0.5% TRP plus zeran ol. No treatment interactions or treatment effects were noted (P>0.10) for daily pin, feed efficiency, and serum melatonin concentration. Ze ranol increased (P<0.06) insulin on d 42 and had minor effects on carc ass composition. In Expt. 2, lambs were fed diets containing 0 or 0.5% supplemental TRP. No effects of TRP were noted (P>0.10) for DMI, dige stibility, and N balance. Lambs fed TRP had lower (P<0.09) serum insul in concentration, but TRP did not affect somatotropin or prolactin con centrations. It is concluded that tryptophan supplementation up to 1% of dietary DM does not alter metabolism in a manner causing difference s in performance, digestion or carcass characteristics.