A note on the response of British Friesian steers to trenbolone acetate and hexoestrol, and to alternation in dietary energy intake

Abstract

ABSTRACTFour steers from a group of eight British Friesian steers were implanted with 300 mg trenbolone acetate and 30 mg hexoestrol at the beginning of a 90-day trial period. The remainder were untreated. They were offered diets that varied in estimated content of metabolizable energy as follows (MJ/day): day 0 to 34 (period A), 100; day 35 to 60 (period B), 50; and day 61 to 90 (period C), 75 increasing to 110. Implanted steers gained significantly more live weight in periods A and C, and lost less in period B, than controls. Implanted steers had significantly elevated concentrations of plasma glucose in period A, and lower values for plasma urea and serum albumin throughout. Differences between control and implanted steers for the other blood constituents studied, including growth hormone, insulin and prolactin, were small and not significant. The main effects of changes in dietary energy intake on blood composition included significant increases in both groups of animals in the concentration of free fatty acids and growth hormone during underfeeding (period B). These concentrations decreased in period C, concomitant with significant increases in the concentrations of insulin and prolactin.