The effect of Zearalanol on seasonal growth rates of cattle in a dry monsoonal environment

Abstract

Liveweight changes of Shorthorn weaner heifers and steers implanted with Zearalanol were compared with those of a control group over eleven months in the Victoria River District of the Northern Territory. Serum urea and pasture nitrogen and phosphorus levels were also recorded. Between August and the following February the treated group showed an 11 per cent (P<0.10) greater liveweight gain, while between February and July they showed a 19 per cent (P<0.001) greater liveweight gain than the controls. Zearalanol had a significant effect on liveweight change fur up to 48 weeks. However, there was no additive effect of a second implant after 27 weeks. No treatment differences in serum urea were observed