Implantation of oestrogenic hormones in Beef Cattle

Abstract

Abstract The carcasses of 24 Aberdeen Angus steers were obtained from an experiment examining the effects of implantation with oestradiol benzoate plus progesterone on rate of liveweight gain. There were eight animals in each of three groups (control, autumn-, and springimplanted). Bone-in carcass conformation was assessed by two methods of jointing, by carcass measurements and quality scores, and by derivation of a carcass wholesale value Index in pence/lb. Implanted animals, which made faster weight gain than controls, produced heavier carcasses. Weights of individual cuts tended to increase proportionately with carcass weight. Adjusted for carcass weight, controls yielded more Kidney and Channel Fat than implanted, and autumn- more than spring-implantation. Group differences were also evident for combinations of“Good Cuts”, and carcass measurements revealed only that controls were fatter, and heavier in relation to their length, than the carcasses of implanted steers. Carcasses from controls were of less total monetary value than those from implanted steers. The highest return/lb of carcass (wholesale value Index) resulted from spring-implantation. This Index was not associated with any of the recorded carcass measurements, nor with carcass scores. Prediction of the Index from individual and groups of cuts was examined and it was concluded that a grouping of relatively high-priced cuts could be used to estimate value/lb.