Growth, hormonal and metabolic response of post-pubertal entire male cattle to trenbolone acetate and hexoestrol

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Abstract
The response of post-pubertal entire male cattle (bulls) to implantation with trenbolone acetate and hexoestrol was studied in two experiments. In experiment 1, eight British Friesian bulls, weighing approximately 359 kg at the beginning of a 90-day experiment, were either sham-implanted or implanted with 45 mg hexoestrol, followed 21 days later with a further implantation of 300 mg trenbolone acetate. In experiment 2, 16 bulls (14 British Friesian and two Simmental < ♂ × (Hereford < 5 × Friesian ♀), weighing approximately 349 kg, were similarly untreated or implanted with 30 mg hexoestrol and 300 mg trenbolone acetate. Treatment with hexoestrol gave a small and non-significant increase in live-weight gain in both experiments. However, live-weight gain and efficiency of conversion of food into live-weight gain were significantly improved in both studies following implantation with trenbolone acetate (P < 0·05). Treated bulls had heavier carcasses and greater mean values for estimated carcass gain (P < 005 in experiment 2). Comparison of mean values for blood metabolites indicated significant differences in concentrations of plasma glucose, free fatty acids and cortisol, and serum total protein, growth hormone, insulin and prolactin. Mean values were significantly lower in treated animals for serum albumin in experiment 2 (P < 001) and for plasma urea in both experiments (P < 0·001; P < 0·05). Treatment with hexoestrol resulted in lower mean concentrations of plasma androgens. These were further reduced following treatment with trenbolone acetate (P < 0·01). The results suggest that the combination of trenbolone acetate plus hexoestrol may improve growth performance, by altering protein metabolism, in post-pubertal entire male cattle. The combination of trenbolone acetate plus hexoestrol appears to have more potent anabolic activity than the endogenous hormones of these animals.