Efeito da torta de nabo forrageiro sobre a cinética de fermentação e degradação ruminal in vitro

Abstract

Considering the need to give the correct destination to co-products generated in the production of biodiesel, as well as nutritionally characterize alternative sources of protein for cattle, the objective of this study was to evaluate ruminal parameters and nutritional value of diets containing 0, 2, 4 and 8 % replacement of cottonseed meal by radish cake utilizing a semi-automated in vitro gas production technique. The evaluation of rumen degradation kinetics, digestibility of DM, OM and NDF, as well as pH, volatile fatty acids and ammoniacal nitrogen determination were performed by incubating 0.3 g of sample in buffered medium. It was observed a cubic effect of the replacement level on the volume of gas corresponding to complete digestion of the substrate, with values of 1.69, 1.70, 1.53, 1.61 mL/mg DM, respectively, for levels 0, 2, 4 and 8 % of substitution. There was a quadratic effect of the level of cottonseed meal replacement by radish cake on the in vitro digestibility of DM, OM and NDF, with maximum points in 2.75, 2.70 and 2.63 % of radish cake, respectively. The cottonseed meal replacement by radish cake influenced total concentration of VFA, concentration of ammoniacal nitrogen and the molar ratio of acetic and propionic acid. The acetate: propionate ratio and pH were not influenced by the substitution of cottonseed meal by radish cake, with average values of 3.36 and 6.93, respectively. It is concluded that the replacement of 2.63 % of the cottonseed meal by radish cake provided better digestibility of DM, OM and NDF of the diets, suggesting that the radish cake can be used in rations of beef cattle, partially replacing the cottonseed meal.