Soja grão e caroço de algodão em suplementos múltiplos para terminação de bovinos mestiços em pastejo

Abstract

Two experiments were conducted to evaluate multiple supplements containing whole soybean (GSOI) and cottonseed (ALG) in relation to standard supplement of corn grain plus soybean meal (FSOJA) in crossbred steers finished at pasture, in the dry season. The supplements were balanced to reach the level of 20% CP, as fed basis. In the first experiment, average daily gain (ADG - kg/day), hot carcass dressing (CD -%) and carcass weight (CW - kg) were evaluated. Twelve Holstein-Zebu crossbred steers, averaging 24 months old and initial weight of 361 kg, were used and managed in three paddocks (3 ha each) of Brachiaria decumbens pasture, daily fed 4 kg of supplement per animal. The observed values of ADG, CD and CW were: 1.056, 52.21 and 241.20; 1.016, 53.04 and 242.55; and 1.137, 53.61 and 247.65, respectively, for the supplements GSOI, ALG and FSOJA, that showed to be equivalent. The objective of the second experiment was to evaluate the influence of the supplements on the behavior of ruminal pH and ammonia concentration. The supplements were those initially described, adding a treatment that included as protein source grinded soybean (GSOM). Five crossbred steers, fistulated in the rumen, grazing Brachiaria decumbens pasture and daily fed 4 kg of supplement, were used. The measures were performed at 0, 2, 4 and 6 hours after supplementation. The ruminal pH was affected by the supplements, and significant reductions were observed only for FSOJA, however, no harmful levels to the ruminal microbes were observed. The average ammonia levels for ALG, GSOI and GSOM were of 7.23, 6.91 and 6.74 mg/dL, respectively, and did not differ from each other, but were inferior than FSOJA (9.51 mg/dL).