EFFECTS OF DIFFERENT DOSES OF ZERANOL ON GROWTH, HEMOGLOBIN, AND CARCASS TRAITS IN VEAL CALVES

Effects of different doses of zeranol on ADG, hemoglobin (Hb), feed ef ficiency (FE), and carcass traits were evaluated in special-fed veal c alves in two trials. On d 0, calves were implanted subcutaneously in t he middle third of the ear with either 0 (control, placebo pellet), 12 , 24, 36, or 48 mg of zeranol. Trial 1 was conducted from February thr ough May 1990 with 120 Holstein bull calves (17 to 21 d of age on d 0) and Trial 2 was conducted from May through August 1991 with 100 Holst ein bull calves (24 to 28 d of age on d 0). Calves were fed on an indi vidual calf basis. Calves in Trial 1 that were implanted with 48 mg of zeranol had improved FE (P < .05) and ADG (P < .05) during Period 1 ( 0 to 43 d). No significant differences in ADG or FE were observed amon g treatments in Trial 2. Hemoglobin levels at slaughter averaged 7.88 +/- .096 and 8.19 +/- .149 g/dL over all treatments for Trials 1 and 2 , respectively. The only postslaughter trait affected by zeranol dose was testicular weight. In both trials, testicular weight at slaughter decreased (P < .05) with increasing doses of zeranol. Dressing percent age tended to be higher for 48-mg implants than for controls but the d ifference was not significant. There were no significant zeranol dose effects on longissimus muscle area, flank color, carcass conformation, or percentage of fore- vs hindquarter weight. These results indicated that higher doses of zeranol improved ADG and FE during the first 6 w k after the trial period (to 8 wk of age), decreased testicular weight , and increased hide-on carcass dressing percentage for calves implant ed with 48 mg of zeranol compared with those that received 0 mg of zer anol.