AbstractTwo grazing trials (GT1; GT2) were conducted over a period of three years, and effect of breed, season, and breed x season was observed on the grazing performance of 87 Holstein, Charbray, and Zebu (mostly Brahman) bulls. The Zebu and Charbray bulls exhibited higher (P < 0.05) average 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 daily gains (ADG) were similar (P > 0.05) during spring, summer, and fall but significantly higher than in the winter months (P < 0.05). Faltering 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 consequence of the combined effects of seasonal restraints on pasture growth and the need of greater dry matter intakes at higher stocking weights. 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, respectively. Costs not considered in the economic evaluation were fence and pasture depreciation, interest on investment, land cost, and overhead expenses.
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