Studies with zeranol implantation of grazing cattle in central-western Queensland

Abstract

During the period 1981 to 1983, nine experiments were undertaken in central-western Queensland to measure the response, by various classes of cattle, to zeranol treatment. Response to a single zeranol treatment by steers aged 18 to 36 months ranged from 0.252 (P<0.005) to 0.035 kg/hd/day (P>0.05) over eight observations at five different sites. There was little advantage at day 606 or day 224 to repeat treatments given either 168 or 84 days after initial treatment. In one experiment, advantages to zeranol treatment were maintained for 606 days post implant. But in another, advantages present at day 224 after implantation, had been eroded away by day 547. Zeranol treatment of spayed cows gave a response of 0.138 kg/hd/day (P<0.005) over 82 days. In two experiments with suckling steer calves, there were non significant advantages of 2 and 7% to zeranol treatment.