Cinética da degradação ruminal da inclusão de grão de soja na suplementação de bovinos de corte em pastagem de Urochloa ruziziensis

Abstract

This study evaluated the ruminal fermentation kinetics of Urochloa ruziziensis supplemented with different proportions of soybean inclusion. Three treatments were evaluated: S10 (10% soybean in concentrate), S30 (30% soybean in concentrate), and S50 (50% soybean in concentrate), each with three replicates, in a completely randomized design. The samples were incubated in vitro in flasks for gas production, with readings taken at different incubation times. The parameters analyzed included: f0 (intercept, associated with the immediate degradation of the soluble fraction), f1 (asymptote, representing the total degradation potential of the substrate), k (fermentation rate, indicating the speed of degradation), and cumulative gas production. The data were adjusted by nonlinear models and submitted to analysis of variance, considering a significance level of 5%. The results show that treatment S10 had a higher f1 value, indicating better utilization of U. ruziziensis fiber, while S30 and S50 showed a reduction in this parameter, associated with the higher lipid content of soybeans. The fermentation rate (k) was higher in treatments with a higher proportion of soybean, suggesting acceleration of initial fermentation, but without a proportional increase in total degradability. It is concluded that moderate proportions of soybean inclusion favor greater fermentative efficiency of the diet.