This experiment was conducted to investigate the effect of supplementation of the diet (concentrate, corn silage, and corn silage and concentrate mixture) with different levels of an exogenous enzyme complex on gas production parameters. For each of the three sections, dietary treatments were: 1) basal diet (no mixing enzyme, control), 2) basal diet + 0.50 g of the enzyme mixture / kg DM, and 3) basal diet + 0.75 g of enzyme mixture / kg DM. Pressures recorded by the manometer method used to predict gas produced from the cultures fermented for 2, 4, 6, 8, 16, 24, 36, 48, 72, 96 and 120 hours after incubation. Unsupplemented diets showed a significant increase in the amount of gas produced in the three portions of the diet (P<0.05). Using the enzyme mixture at the level of 0.75 g/kg DM, caused a significant decrease in the amounts of gas produced in the mixture of concentrate and corn silage, and corn silage (P<0.05). Gas production rate was also significantly affected by different levels of the enzyme mixture (P<0.05). It seems that enzyme levels used in this experiment, did not improve the potential of gas production and nutritive value of different portions of ration. Further study is needed to achieve the effect of enzyme supplementation on gas production parameters.