Published online by Cambridge University Press: 02 September 2010
Twenty-five Greyface wether lambs were allocated at approximately 40 kg live weight to be slaughtered, to be untreated controls, or to be implanted with 57·5 mg trenbolone acetate plus 8·1 mg oestradiol-17β (treatment To8), 60mg trenbolone acetate plus lOmg oestradiol-17β (treatment To10) or 70mg trenbolone acetate plus 12 mg zeranol (treatment TZ). The control and treated lambs were slaughtered after 63 days. Effects on live-weight gain were small and not significant. On average, hormonal treatments resulted in: (a) significant increases in dressing percentage, gain in carcass weight and carcass protein, kidney weight (g/kg live weight), depth of thorax and in the activity of liver tyrosine amino transferase; and (b) variable reductions in hind leg length, concentration of plasma urea and (g/kg live weight) kidney fat, mesenteric fat and fleece. Significant differences recorded between treatments included the conversion of food into carcass protein (treatments To8 and TO10 v. TZ) and mesenteric fat (g/kg live weight) and fat cover at the 12th rib (treatment To8v To10).