The effect of implantation of trenbolone acetate and oestradiol-17β in wether lambs at two initial live weights on concentrations of steroidal residues and blood glucose, urea and thyroid hormones

Abstract

Thirty-two Border Leicester ♂ × Scottish Blackface ♀ wether lambs aged about 5 months were divided into two groups on the basis of live weight such that group Gl contained the 16 lightest lambs and group G2 the 16 heaviest. Lambs in group Gl were subdivided equally at random either to be sham-implanted controls (group C1) or to be implanted with 35 mg trenbolone acetate (TBA) + 5 mg oestradiol-17β (group T1) at 24 kg initial live weight. The lambs in group G2 were also subdivided into two groups (groups C2 and T2) and similarly treated approximately 1 month later at 37 kg initial live weight. The lambs were offered ad libitum a good-quality diet. They were slaughtered 60 days after implantation. Comparisons were made for the main effects of hormonal treatment and initial live weight.Concentrations in blood of 17-β-hydroxy-trenbolone (TBOH) and oestradiol-17β (OE) measured by radioimmunoassay peaked within 1 to 3 weeks after implantation and declined thereafter. Maximum concentrations and concentrations at slaughter respectively were 1·46 and 0·32 μg/l (group T1) and 0·78 and 0·28 μg/l (T2) for TBOH and 85 and 33 μg/1 (T1) and 59 and 37 ng/l (T2) for OE. Values up to week 7 were consistently greater in implanted animals in group T1 than in group T2. Hormonal implantation decreased the concentrations of total plasma triiodothyronine and thyroxine and urea and increased values for glucose up to week 5 or 6 after implantation. The animals in group G1 compared with G2 had, on average, variably lower concentrations in plasma of triiodothyronine, thyroxine, glucose and urea.The highest concentrations of solvent-extractable residues were obtained in samples of kidney and liver (up to about 500 ng/kg for TBOH and 180 ng/kg for OE) with intermediate levels for fat and lowest levels for muscle. Conjugated trenbolone ranging from 45 to 186 ng/kg was present in samples of kidney, liver and perinephric fat. Trenbolone acetate was detected only in samples of fat. Variable effects of live weight at implantation on residue levels were recorded.