Substitution of soybean meal for cottonseed meal in multiple supplements for grazing beef heifers in the dry season

The objective of this study was to evaluate the effect of substituting soybean meal for cottonseed meal in multiple supplements on the nutritional characteristics and performance of beef heifers in their post- weaning phase on Brachiaria decumbens pastures during the dry season. Twenty-four Nellore beef heifers (average initial age and weight of 8 mo and 210±6 kg, respectively) were used. The design was completely randomized, with four treatments and six replicates. Supplements contained approximately 30% crude protein (CP) and a progressive substitution of soybean meal for cottonseed meal (0, 50 and 100%). The control animals received only a mineral mixture ad libitum, and those on the other treatments received supplementation at 1.0 kg/animal/day. No differences were found in ADG between supplemented and control animals (P>0.10). Supplementation increased crude protein (CP) intake only (P0.10) the intake of supplemented animals. Supplementation elevated the apparent digestibility coefficients (P0.10). A positive linear effect (P<0.10) of the level of substitution of soybean meal for cottonseed cake was observed on the digestibility of OM, NFC and TDN. Supplementation and the level of substitution had an effect (P0.10). Substitution caused a decreasing linear effect (P<0.10) on microbial nitrogen/nitrogen intake ratio (MICNR). In conclusion, substitution of soybean meal for cottonseed meal in multiple supplements during the dry season does not impair the productive performance of beef heifers.Objetivou-se avaliar o efeito da substituição do farelo de soja pelo farelo de algodão em suplementos múltiplos sobre as características nutricionais e desempenho produtivo de novilhas de corte em fase de recria em pastagens de Brachiaria decumbens no período da seca. Foram utilizadas 24 novilhas de corte nelore com idade e peso médio inicial de 8 meses e 210±6 kg, respectivamente. O delineamento foi inteiramente casualizado com quatro tratamentos e seis repetições. Os suplementos continham aproximadamente 30% de proteína bruta (PB) e substituição progressiva do farelo de soja pelo farelo de algodão em 0, 50 e 100%. Aos animais do tratamento controle foi fornecida apenas mistura mineral ad libitum e aos demais tratamentos foram fornecidos 1,0 kg/animal/dia de suplemento. Não houve diferença de GMD entre os animais suplementados e os animais controle (P>0,10). A suplementação aumentou apenas o consumo de proteína bruta (PB) (P0,10) o consumo nos animais suplementados. A suplementação ampliou os coeficientes de digestibilidade aparente (P<0,10) da MO, PB, CFN e NDT com exceção do EE e da FDNcp (P>0,10). Observou-se efeito linear positivo (P0,10). Foi verificado efeito linear decrescente (P