RESUMEN
This study evaluated levels of replacement of soybean meal by castor bean meal in the finishing crossbred steers on Brachiaria brizantha cv. Marandu pasture during the rainy-dry transition period. Forty Holstein-Zebu crossbred steers with an average initial weight of 395.93 ± 10 kg were randomly allocated to four treatment groups that were supplemented with concentrate levels of replacing (0, 290, 613, and 903 g/kg DM of the supplement; at 0.4% body weight [BW]). The experimental period was 120 days. A completely randomized experimental design was adopted; with regression analysis using the computational software package (SAS 9.2, USA). Intake and digestibility of dry matter (DM) and nutrients and animal performance were evaluated. The replacement levels did not influence (P > 0.05) the intakes of DM (kg/day), organic matter (OM, kg/day), neutral detergent fiber (NDF, kg/day and %BW), non-fibrous carbohydrates (NFC, kg/day), or total digestible nutrients (kg/day). However, the intake of crude protein (CP) and ether extract (EE, kg/day) decreased as the replacement levels were increased (P < 0.05). The digestibility of DM, OM, NDF, and EE did not change, whereas CP digestibility decreased linearly and NFC digestibility increased linearly (P < 0.05). The replacement levels did not affect (P > 0.05) final body weight, average daily gain, feed conversion, and carcass yield. Castor bean meal can replace up to 903 g/kg DM of soybean meal in the composition of the supplement without compromising the performance of steers on Marandu pasture during the rainy-dry transition period.