Effects of some anabolic agents on the growth, carcass and tissue composition of barley-fed entire and castrated male Friesian cattle

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Abstract
Thirty-eight barley-fed entire and castrated male Friesian calves were used to examine the effects of different implanted anabolic agents on growth and carcass and tissue composition. Entire males were implanted with trenbolone acetate plus hexoestrol alone or following an earlier implantation of zeranol, or with zeranol alone. Control bulls (no implant) and steers treated with trenbolone, acetate plus hexoestrol were also studied. The anabolic agents tended to increase growth rate in bulls, and caused an increase in fat deposition. Treated steers had more abdominal fat than all bulls, but did not have more carcass fat. However, the carcasses contained less saleable meat and had a lower retail value because of lower lean-to-bone ratio. There were no significant differences between any of the groups in the proportions of lipid and water in the lean tissue. Transporting the bulls resulted in a high pH and a dark colour in m. tongissimus. The results suggest that anabolic agents have small biological effects which directly modify the quantitative and qualitative meat production characteristics of bulls.