Effects of an anabolic treatment before puberty with trenbolone acetate-oestradiol or oestradiol alone on growth rate, testicular development and luteinizing hormone and testosterone plasma concentrations

Scrotal circumference, growth and hormonal status after prepubertal anabolic treatments were studied in 18 conventional Belgian White Blue bulls from 3 to 13 mo of age. Young bulls were assigned into three groups: six untreated (control) bulls, six bulls implanted with 140 mg trenbolone acetate + 20 mg oestradiol (Revalor; TBA-E2) and six bulls treated with 45 mg oestradiol (Compudose; E2). Mean scrotal circumference was similar in the three groups at Day O (between 13.0 +/- 0.3 cm to 13.4 +/- 0.7 cm). From Days O to 230, scrotal circumference was strongly inhibited in implanted bulls, 23.2 +/- 1.4, 21.7 +/- 1.0 cm, respectively, for TBA-E2 and E2 at Day 210, as compared with 29.5 +/- 2.2 cm in control bulls (P < 0.001). Afterwards, differences lessened gradually and no significant divergence was observed between the three groups from Day 310. Average plasma luteinizing hormone (LH) concentrations were similar in the three groups throughout the assay. Mean testosterone levels remained extremely low upto Day 150 in TBA-E2 and E2 groups (0.6 +/- 0.6, 1.2 +/- 0.7 ng/ml, respectively) before they increased abruptly and reached values observed in control bulls at Day 180 (4.0 +/- 1.9 ng/ml). The pulsatil character of LH and testosterone profiles was abolished by the anabolic treatments. Luteinizing hormone-releasing hormone (LHRH) injection was followed by an immediate and sharp increase in plasma LH concentrations in all groups at Day 0. Anabolic treatments strongly reduced LH and testosterone responses to LHRH in treated groups.