Response of castrated male sheep to oestrogenic and androgenic compounds implanted alone or in combination

Abstract

Forty-eight Greyface wether lambs, aged about 6 months and weighing 32 kg on average were used. They were allocated to be treated, by subcutaneous implantation in the upper surface of the ear flap, with the naturally occurring steroids oestradiol-17ji (O), testosterone (T) or the synthetically produced androgen trenbolone acetate (TA). Treatment groups were as follows: sham-implanted controls (C); 50 mg O (slow release formulation) (O); 40 mg TA (compressed pellets} (TA); 50 mg T (compressed pellets) (T); 15 mg O + 40 mg TA (TAO); 15 mg O + 50 mg T (TO). Combined implants were placed in close proximity under the skin of the same ear. The lambs were offered, to appetite, a good quality diet containing per kg dry matter (DM) an estimated 12-0 MJ metabolizable energy and 150 g crude protein. Comparisons were made for the main effects of O and the androgens T and TA. Main effects due to O were increased DM intake, live-weight gain (LWG) empty body weight (EBW), chilled carcass iveight (CCW), carcass crude protein (CP) deposition, plasma insulin concentrations and teat length with reductions recorded for the proportion but not weight of fat in the carcass, plasma urea and thyroxine concentrations. Treatment with androgens did not, on average, influence LWG or other indices of growth performance or carcass composition other than to produce significant increases in carcass phosphorus deposition and reduction in the depth of thorax. Significant increases in the iveight of penile tissue and reductions in teatlength were recorded. There was evidence for a greater androgenic effect on penile tissue and anti-oestrogenic effect (on teat length) of TA compared with T at the concentrations used. TA also reduced the weight of the thymus gland, an effect reversed in the presence ofO.Analysis of plasma taken from the vein contralateral to the site of implantation showed that O concentrations were reduced in the presence of TA and T, and that O had no effect on the concentrations of androgens measured. Concentrations ofT and 17 p-hydroxy-trenbolone in blood were of a similar order, which for T is typical of postpubertal entire male sheep. The results suggest that O treatment was effective in promoting growth and carcass CP deposition which was not increased by T or TA, despite the presence of these androgens at biologically active concentrations in blood. This effect appears to differ from the additive effects frequently obtained for castrated male cattle.

Hormones in international meat production: biological, sociological and consumer issues

“…Similarly, TB-17β-OH was shown to have a greater affinity for the bovine Pr receptor than Pr (1:1•37) and to compete poorly with DHT for the human SHBG. Given alone, TBA had similar limited anabolic activity to T in stimulating growth and carcass protein deposition in castrate male sheep although TBA did exhibit up to 50 % greater apparent androgenic activity in increasing weight of sex hormone-sensitive tissues (Galbraith et al 1990(Galbraith et al , 1997. Combinations of T and TBA treatment showed additive effects for those androgenic indices.…”

“…Implants variously contain dose levels of 8-20 mg E 2 -17β or oestradiol benzoate; 100-200 mg T or T-propionate; 200 mg Pr; 40-300 mg TBA; 36 mg Z, with MGA administered in the diet at 0·25-0·5 mg/d. Effects of combined implants (E 2 -17β+Pr; E 2 -17β+T; E 2 -17β+TBA; Z+TBA) include potentiation of effectiveness of single ingredient treatments, reduction in sex hormone-related behavioural effects and more controlled release of hormone from the implant (for example, see Heitzman, 1976;Galbraith et al 1997). Castrated male cattle generally exhibit the greatest response in growth rate, efficiency of feed conversion, N retention, skeletal muscle hypertrophy and lean tissue deposition occurring in the relative absence of endogenous sex hormones, with smaller responses in post-pubertal heifers and bulls.…”

“…Castrated male cattle generally exhibit the greatest response in growth rate, efficiency of feed conversion, N retention, skeletal muscle hypertrophy and lean tissue deposition occurring in the relative absence of endogenous sex hormones, with smaller responses in post-pubertal heifers and bulls. Oestrogens, in addition to producing sex hormone-related side effects (Galbraith et al 1990(Galbraith et al , 1997Zarkawi et al 1991a;Wetteman & Lehman, 1997), produce the greatest anabolic responses. These may be enhanced by combination with androgens such as TBA (Preston, 1999) although not T or the β-agonist cimaterol (Galbraith et al 1990(Galbraith et al , 1997 with responses differing between cattle and sheep.…”

Thymic involution in calves treated with clenbuterol

“…Since the early 1980s, the usefulness of clenbuterol, a β‐agonist drug, as a growth promoter has been well documented (Williams and others 1987). With respect to the thymus, the influence of corticoidal and steroidal anabolic treatments on the involution of the thymus has also been characterised (Gropp and others 1976, Weinstein and Isakov 1983, Galbraith and others 1997, Groot and others 1998, Schilt and others 1998). Nevertheless, very little is known about the effect of clenbuterol on lymphatic tissues, even though immunodepressive effects have been reported in clenbuterol treatment (Spencer and Oliver 1996).…”