Growth and subsequent fertility of cows implanted during pregnancy with trenbolone acetate and oestradiol

Abstract

Under extensive grazing conditions in Australia the pregnancy status of cows is often not known. It is therefore conceivable that if anabolic steroids are administered to females, some may be pregnant. This experiment examined the consequences of such an action. Sixty-nine multiparous cows were grazed together from the sixth to eighth month of pregnancy in July until calf weaning the following May. Thirty-five were implanted in the ear with Revalor« (200 mg trenbolone acetate and 20 mg oestradiol-17G) only once at the commencement of the experiment in July. The remainder served as controls. Treated cows had significantly (P < 0.01) higher liveweight gains pre-calving (0.39 v. 0.28 kg/day) and significantly (P < 0.05) lighter calves at birth (32 v. 35 kg) than the controls. There was no effect of treatment on calf survival before or after birth, calf growth rate or cow fertility after calving.