The effects of hormones, other pharmacological agents and nutrition on plasma triglycerides and carcass composition in lambs and steers

Abstract

The effects of recombinantly derived growth hormone (GH), oestradiol-17$ plus trenbolone acetate, clofibrate, melatonin and fasting on basal plasma triglycerides (TG) and TG entry rate were determined in wether lambs given lucerene/barley pellets ad libitum. Clofibrate was administered at 2 X 0-5 g capsules orally, GH (0-25 mg/kg live weight) was injected subcutaneously daily whilst oestradiol-17fi, oestradiol-17$ plus trenbolone acetate and melatonin were slow release implants (either 4 or 4-8 mg, 4 nig and 20 nig and 18 mg respectively) placed subcutaneously in the ear. Both fasting and oestradiol treatments raised basal TG levels without influencing TG entry rates, defined as the maximum rate of change of plasma TG 3 to 6h following a dose of Triton WR1339 of at least 0-2 g/kg live weight. Entry rates were similar to those previously reported for goats but were higher than those reported for sheep. Triton WR1339 used to determine entry rates was found to reduce food intake at all levels in some sheep despite reports to the contrary. Among the various treatments, only oestradiol-17$ and trenbolone acetate influenced body composition as determined by chemical analysis of minced carcasses, resulting in an increased gain of carcass protein and decreased gain of carcass fat. Clofibrate, melatonin and Triton, if allowance is made for Triton-induced loss in food intake, had no clear effects on body fatness. Overall the effects of hormones on plasma TG appeared to be small and it seems improbable that plasma TG are involved in effects of hormones on fatness.

Effect of a combined trenbolone acetate and estradiol implant on feedlot performance, carcass characteristics, and carcass composition of feedlot steers.

“…However, Lee et al (1990) found that separate implants of TBA and E 2 caused a decrease in dry matter and fat content of the 9-10-11th rib section in growing steers, but these differences disappeared during the finishing phase. In lambs implanted with a lower dose of TBA+E 2 (20/4), percentage of carcass protein increased and percentage of carcass fat decreased compared with nonimplanted lambs (Payne and Cope, 1991). Conversely, Hunt et al (1991) reported that, in steers, TBA and E 2 administered as separate implants increased percentage of fat in the 9-10-11th rib section compared with nonimplanted steers.…”

“…In steers, TBA+E 2 (140/28) increased daily fat gain (Perry et al, 1991). However, fat gain was reduced in lambs implanted with TBA+E 2 (Payne and Cope, 1991).…”

Melatonin and farm animals: Endogenous rhythms and exogenous applications

“…In several published reports, no nocturnal elevation in plasma melatonin was observed [Brandt et al, 1986;Minton et al, 1989;Peacock et al, 1990;Diekman et al, 1990, 19921 and, in one study, melatonin appeared to increase following illumination [DeBoer and Hacker, 19861. These studies have led to the belief that the endogenous secretion pattern of melatonin in the domestic pig is very different from that in other mammals.…”