The influence of anabolic steroids on growth, body composition and lipid metabolism in sheep
A series of three experiments were conducted to investigate the effect of anabolic compounds, oestradiol-17beta (OE2), trenbolone acetate (TBA) and testosterone, on the growth and lipid metabolism of wether lambs. In experiment I some aspects of lipid metabolism were studied. In experiments II and III, measurements were made of aspects of growth, lipid metabolism, in addition to the concentration in blood of some metabolites, endogenous hormones and active ingredients of implants. In general, OE2 treatment increased total dry matter, crude protein, ether extract and total ash in the carcases in both experiments II and III, while combined implantation of OE2 with either TBA or testosterone in experiment II, decreased the ether extract content of the carcase. In experiment I, initial liveweight, but not hormonal treatment was shown to influence plasma total cholesterol levels particularly during the early part of the experiment. In experiments II and III, OE2 treatment tended to increase the concentration of plasma total cholesterol. However, the effects of OE2 in increasing plasma total cholesterol was reduced when implanted along with either TBA or testosterone in experiment II. In experiment III, the average proportions of plasma low density lipoproteins (LDL) and high density lipoprotein (HDL) were 44% and 56% respectively. Treated lambs had a significantly lower proportion of LDL at week 2 but were significantly higher at weeks 5 and 6 after the first implantation. The activity of plasma lecithin: cholesterol acyl transferase was significantly lower at week 6 of first implantation in treated lambs as compared to untreated controls. In experiment II, the activities of acetyl CoA carboxylase (CBX) fatty acid synthetase (FAS), NADP-malate dehydrogenase and NADP- isocitrate dehydrogenase, tended to increase in adipose tissue due to OE2 treatment. In liver NADP-isocitrate dehydrogenase and NADP- malate dehydrogenase activities tended to decrease, while the activity of ATP-citrate lyase tended to decrease in adipose tissue but to increase in liver. The effects of TBA and testosterone on the activities of the above enzymes were similar to that of OE2 treatment except that testosterone treatment had a significant effect in increasing the activity of NADP-isocitrate dehydrogenase but decreasing the activity of ATP-citrate lyase in adipose tissue. In experiment III, the effects on enzyme activities were totally opposite to that observed in experiment II due to OE2 treatment.