The response of male zebu calves to creep feeding, castration, diethylstilbestrol and supplental feeding on pasture

Abstract

Supplements were fed to male Zebu calves grazing Colonial Guineagrass pastures during pre and post-weaning periods to determine their effect upon animal performance and carcass characteristics. The effect of castration and implantation of diethylstilbestrol was also studied. The rate of gain during the pre-weaning period and post-weaning winter period was increased by the supplements when fed at 2kg per animal per day. A high-protein supplement was superior to a low-protein supplement during the winter-dry season when the pasture was of poor quality, but this advantage disappeared during the following summer season. During the total period of 370 days, the calves receiving the supplements weighed an average of over 30kg more than animals receiving no supplement. (See Table 5). Castration reduced the rate of gain by 56g per animal per day and stilbestrol increased the rate of gain by 60g per animal per day, so that the response to stilbestrol was equal to the detrimental effects of castration (Table 11). With respect to carcass characteristics, the supplements increased the dressing percentage (Tables 13 and 14) and the size of the rib-eye area, (Table 17) but had no effect upon the percentage of kidney fat (Table 15) or thickness of surface fat (Table 16). The steer carcasses had a higher percentage of kidney fat, a greater thickness of surface fat, but a smaller rib-eye area than the corresponding bull carcasses. The implantation of stilbestrol appeared to have no effect upon these characteristics, although it did increase the dressing percentage.