MINERAL AND NITROGEN BALANCE IN LAMBS IMPLANTED WITH ZERANOL

Fourteen crossbred wether lambs (average BW, 28 kg +/- 213) were eithe r implanted (12 mg of zeranol) or not implanted and group-fed an 86% c oncentrate diet for 21 d. Lambs were then moved to metabolism stalls a nd fed .8 kg/d for a 10-d stall adjustment followed by a 7-d total col lection of feces and urine. Feed, feces, and urine were analyzed for C a, P, Mg, Zn, Mn, Cu, and N. Apparent absorption of Mn, Cu, and N, wer e similar for implanted and nonimplanted lambs. Zeranol did not affect (P > .10) the retention of Mn or Cu. Zeranol decreased fecal excretio n of Ca 22% (P < .01), P 27% (P < .05), Mg 11% (P < .03), and Zn 9% (P < .10). This increased apparent absorption of Ca 88% (P < .01), P 193 % (P < .05), Mg 9% (P < .05), and Zn 45% (P < .10) in zeranol-treated lambs. Urinary excretion of all nutrients analyzed was similar for imp lanted and control lambs with the exception of N, which was reduced by 24% (P < .06) in implanted lambs. The amount of Ca, Mg, and Zn retain ed increased 98% (P < .01), 138% (P < .03), and 60% (P < .10), respect ively, in implanted lambs compared with controls. These results indica te that zeranol improved N balance and enhanced the absorption and ret ention of Ca, P, Mg, and Zn in lambs.