The effects of implanting prepuberal dairy heifers with anabolic steroids on live-weight gain, blood and urine composition and milk yield

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Abstract
Twenty-seven British Friesian heifer calves were housed as a group but fed individually barley-lucerne pellets according to a scale related to body weight. At 16 weeks and again at 31 weeks of age nine calves were implanted subcutaneously at the base of the ear with 300 mg trenbolone acetate (group T), nine calves were similarly implanted with 140 mg trenbolone acetate and 20 mg oestradiol-17/? (group TE) and the remaining nine calves were sham implanted (group C).As a result of increased feed conversion ratios, body-weight gains were significantly greater in group T (0–80 kg/day) and group TE (0–87 kg/day) than in group C (0–72 kg/ day) during the 15 weeks following the second implant, but there was no significant difference between groups following the first implant.Following both implants in groups T and TE the mean concentrations of urea and albumin in serum decreased, and that of globulin increased. The mean urea: creatinine ratio in the urine of animals in groups T and TE relative to that in group C also decreased.The heifers were served by an Aberdeen Angus bull at the first and, when they occurred, subsequent oestruses. Following calving the mean milk yields in the first lactation in group T (641 kg in 96 days) and group TE (1993 in 212 days) was considerably lower than in group C (3636 kg in 293 days). The udder size in both groups of animals treated with the anabolic steroids was markedly reduced. It is concluded that despite an improvement in feed conversion ratios and body-weight gains, trenbolone acetate should not be administered to prepuberal heifers which will be retained for breeding and milk production.