Sustained growth promotion of steers, using anabolic steroids

Abstract

This experiment tested the hypothesis that sustained growth promotion of steers could be achieved by alternate use of oestrogenic and androgenic anabolic steroids. Twenty-one high grade Brahman (Bos indicus) steers were divided into 3 groups of 7 and allocated to 1 of the following treatments: control; implantation in the ear with 45 mg oestradiol-17β for approximately 100 days followed by treatment with testosterone propionate (this rotation occurred twice); implantation with 45 mg oestradiol-17β at approximately 100-day intervals. Steers were housed in individual pens in an animal house and fed a restricted diet to regulate their growth rate to about 0·6 kg/day over a 58-week period. At intervals during the first 30 weeks, steers were transferred to metabolism crates and their nitrogen retentions measured. At the end of the experiment the steers were slaughtered and their carcass characteristics determined. The mean growth rates of the steers treated with 2 steroids alternately (0·75±0·06 kg/day) and of steers treated continuously with oestradiol-17β (0·72±0·06 kg/day) were significantly (P = 0·01) higher than that of control steers (0·62±0·10 kg/day). Treatment with oestradiol-17β during the first implant period was associated with higher (P < 0·05) nitrogen retentions in the first weeks after implantation with attenuation of the advantage at the end of the 100-day period. At slaughter, steers from both steroid treatment strategies were almost 60 kg heavier (P < 0·05) than the controls, with carcasses about 30 kg heavier. Steers treated continuously with oestradiol-17β had significantly (P < 0·05) thicker subcutaneous fat cover at the P8 rump site (19·4 mm) than the controls (12·4 mm) or those treated during the final period with testosterone propionate (12·3 mm). It was concluded that sustained growth promotion of steers using anabolic steroids can be achieved.