The effects of a combined androgenic-oestrogenic anabolic agent in steers and bulls 1. Growth and carcass composition

Abstract

Twenty-one pairs of male cattle twins, 10 of which were monozygotic, were used in a study of the effects of a combined implant of trenbolone acetate (140 mg) and oestradiol-17B (20 mg) on growth and carcass composition. There were three comparisons within pairs: (1) between bulls and steers (no implants); (2) between bulls and implanted steers; and (3) between bulls and implanted bulls.Implants were given twice, at 44 to 73 days and at 300 days of age. Animals were slaughtered at 400 days following recorded consumption of a complete pelleted diet given ad libitum. Carcasses were separated into tissues and lean and fat were chemically analysed. The effects of castration and/or implantation on growth and carcass composition were assessed by comparison with the untreated (control) bull values within each group and expressed as a ratio (treatedxontrol). These ratios were then compared between groups.Bulls were significantly heavier than steers at slaughter (29-6 kg, P < 005), but were not heavier than implanted steers. Implantation of steers tended to increase appetite; it proportionately increased lean and protein production by about 0-1, and partly reversed the effects of castration on the length of limb bones and the weights of reproductive organs and hide. The proportions of carcass tissues were very similar in the untreated and implanted steers. In bulls, implantation increased the weight of fatty tissue in the subcutaneous and intermuscular depots, but it had small effects on other carcass characteristics.203

Energy partitioning, tissue growth and appetite control

“…When the propensity to deposit fat during growth was reduced the pigs were able to achieve their target for protein deposition at a lower food intake. These findings and those of Fisher et al (1986) are entirely consistent with my general hypothesis, although they do not exclude alternative explanations.…”

“…' Fisher et al (1986) have measured effects of castration and implantation with anabolic steroids on appetite and growth in twin cattle. Implanted castrate males achieved a lean tissue growth rate approximately halfway between that of castrate and entire males but deposited fat at the same rate as castrates.…”

“…In the studies of Fisher et al (1986) and Campbell et al (1988) the nature of growth was varied hormonally and the animal was able to control nutrient intake but not quality. In elegant recent experiments by Kyriazakis & Emmans (1991), however, young pigs have been allowed to express their impetus for growth by regulating both the quantity and quality of nutrient intake.…”

Effects of trenbolone acetate on carcass characteristics and serum testosterone and cortisol concentrations in bulls and steers on different management and implant schemes.

“…Similarly, Silcox et al (1986) found that bulls implanted with Z or Z plus TBA were similar to NIB in marbling. However, Fisher et al (1986b) reported that bulls implanted with TBA plus estradiol had more marbling than NIB, whereas IS seemed to have less marbling.…”

The effects of a combined androgenic-oestrogenic anabolic agent in steers and bulls 2. Muscle weight distribution, partition of body fat and carcass value

“…However, because the implanted steer yielded a greater weight of lean tissue and was relatively more efficient at doing so (Fisher et al, 1986b), the next result was that implantation of the steer was economically advantageous. Fatty tissues were not so responsive to implantation.…”