Fifty four spring born Hereford bullocks, with an average body weight of 208 kg and 7 to 8 months of age, were used to improve their gains and carcass. The experimental period began in June 17, 1983, in semi-roofed pens, warm beds and a supplementation with silage plus 0.0 (C0). 1.5 (C1). and 2.5 (C2) kg concentrate/an./day. Since September 30, the animals grazed non-irrigated clover-ryegrass pastures. One third of each group was castrated (E1) in Oetober 11 and the second third was castrated in November 15 (E2). leaving the rest as bulls (E0). The three groups were kept in rotational grazing, with 3 an.lha. On December 29, they were sold and slaughtered the next day. During winter, gains (kg/an./day) were 0.237 a, 0.497 b, and 0.759 c (P < 0.05) and in spring, they were 0.938 a, 0.882 a and 0.764 b, for treatments C0, C1 and C2, and 0.858 ab, 0.941 b and 0.786 a, for E0, E1 and E2, respectively. Yielding per cent and carcass length were influenced by winter feeding, being higher for C2 (P < 0.05). Sirloin area was higher for bulls than for steers. Fat layer (mm) was 1.8 a, 2.4 b and 2.7 b, for C0, C1 and C2 and 1.6 a, 3.0 b and 2.3 c, for E0, E1 and E2, respectively( P < 0.05). |
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