The objective of the current experiment was to determine the effects of increasing levels of palm kernel cake in a finishing diet on feed intake, digestibility, performance, ingestive behaviour and carcass traits in zebu bulls. Thirty-two Nellore bulls (420 ± 25.0 kg initial body weight [BW] and 24-months-old), were assigned randomly to individual pens with four treatments (0, 70, 140 and 210 g/kg of palm kernel cake by total dry matter [DM]) and eight replicates per treatment. The inclusion of palm kernel cake linearly decreased DM, crude protein and non-fibrous carbohydrate intake and increased ether extraction intake and digestibility. There was a linear decrease in final BW and hot carcass weight (HCW) associated with palm kernel cake inclusion in the bull diet. However, the gain : feed ratio was similar among the diets. Eating and rumination rates (g DM or neutral detergent fibre/h) were reduced, whereas the total chewing time and idling (min/day) were not affected by palm kernel cake inclusion. There were no effects of palm kernel cake inclusion on most quantitative carcass characteristics and qualitative carcass attributes (subcutaneous fat thickness, longissimus muscle area, colour, texture and marbling). The inclusion of palm kernel cake (up to 210 g/kg total DM) in beef cattle finishing diets decreased eating and rumination rates, thereby decreasing average daily gain and, consequently, final BW and HCW. However, qualitative carcass attributes were not affected by the use of palm kernel cake.
RESUMOObjetivou-se avaliar a substituição do farelo de soja por torta de amendoim no concentrado da dieta de novilhos, por meio do comportamento ingestivo e respostas fisiológicas. Foram utilizados cinco novilhos, dispostos em um quadrado latino 5 x 5. As dietas foram compostas de feno de tifton, milho moído, farelo de soja e torta de amendoim, constituídas de zero (100% de farelo de soja), 25, 50, 75 e 100% de substituição por torta de amendoim no concentrado. Os níveis de torta de amendoim não influenciaram (P>0,05) as eficiências de ingestão e ruminação da matéria seca e da fibra em detergente neutro. Em relação às atividades comportamentais, o único parâmetro em que se observou efeito da substituição foi o número de períodos de ócio no turno da manhã (P<0,05), no qual se constatou efeito linear crescente. A taxa de secreção salivar e a quebra de partículas foram semelhantes, pois não houve efeito (P>0,05) das dietas sobre as características de mastigação. Como não houve efeito (P>0,05) das dietas sobre as frequências respiratória, cardíaca e a temperatura retal, o calor endógeno produzido pela fermentação ruminal foi equivalente. A torta de amendoim, por conter aflatoxinas, quando fornecida em alta relação volumoso x concentrado, pode substituir o farelo de soja na dieta de novilhos, pois ocasiona comportamento ingestivo e respostas fisiológicas semelhantes.
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