The kinetics of gas production and in vitro ruminal degradation of diets contained replacement of soybean meal (SBM) by detoxicated castorbean meal (DCBM) (0, 15, 30 and 45% of substitution) were evaluated in this study. Values of gas production of non-fibrous carbohydrates (Vf1), fibrous carbohydrates (Vf2) and total carbohydrates (V) showed quadratic behavior, and by observation of equations can be obtained inclusions of 25% the V and Vf1 obtained maximum values of 174.7 and 237.8 ml gas / g DM, respectively. The potential degradability (PD) and effective degradability (ED) of dry matter showed quadratic behavior and by observation of equations can be perceive that up to 18.0% there was an increase in the values of PD and ED that obtained maximum values of 93.7% and 55.7%, respectively. The replacement of SBM by DCBM from 15 to 30% increased the kinetics of gas production and rumen degradation.(AU)