COMPARISON OF HOLSTEIN, CHARBRAY, AND ZEBU BULLS FOR BEEF-PRODUCTION UNDER ROTATIONAL GRAZING - I - GRAZING PERFORMANCE AND ECONOMIC-EVALUATION

Two grazing trials (GT1; GT2) were conducted over a period of three ye ars, and effect of breed, season, and breed x season was observed on t he grazing performance of 87 Holstein, Charbray, and Zebu (mostly Brah man) bulls, The Zebu and Charbray bulls exhibited higher (P < 0.05) av erage daily gains (0.60, 0.57 vs. 0.45 kg) and mean final weights (502 .5, 478.4 vs. 438.9 kg) than the Holstein bulls. Overall, average dail y gains (ADG) were similar (P > 0.05) during spring, summer, and fall but significantly higher than in the winter months (P < 0.05). Falteri ng ADG started in late autumn of GT1 and in late winter of grazing GT2 , depending on when the cattle were started on test, and were the cons equence of the combined effects of seasonal restraints on pasture grow th and the need of greater dry matter intakes at higher stocking weigh ts,The breed x season interaction was significant (P < 0.05). Holstein bulls had significantly lower (P < 0.05) ADG in summer and fall, but no significant difference was found among breeds in winter and spring. Net returns per animal after considering variable costs were $154.72, $134.49, and $77.47 for the Zebu, Charbray, and Holstein bulls, respe ctively. Costs not considered in the economic evaluation were fence an d pasture depreciation, interest on investment, land cost, and overhea d expenses.