The effects of increasing doses of three exogenous enzymes preparations with fibrolytic activity (FIB - 0, 0.6, 1.2, 1.8, and 2.4 mg mL-1liquid volume incubated), amylolytic activity (AMZ - 0, 0.05, 0.10, 0.15, and 0.20 mg mL-1liquid volume incubated), and proteolytic activity (PRO - 0, 0.05, 0.10, 0.15, and 0.20 mg mL-1 liquid volume incubated ) on gas production (GP), kinetic parameters, and fermentation profile of Brachiaria brizantha cv. Marandu were evaluated using the in vitro gas production technique. Ruminal liquid was obtained from two rumen-cannulated Santa Ins sheep maintained on pasture. Accumulated gas production was measured during 96 hours of incubation, measured at 18 different time points. The determined parameters were pH, asymptotic gas production (mL g-1), rate of gas production (h-1), lag time (h), organic matter digestibility (OMD, g g-1 DM), metabolizable energy (ME, MJ kg-1 DM), and neutral detergent fiber digestibility (NDFD, mg g-1 DM). Increasing the FIB dose linearly increased (P < 0.05) the asymptotic gas production. However, the rate of gas production and the lag time showed linear decreases (P < 0.05). Addition of FIB also linearly increased (P < 0.05) the GP at all incubation times, as well as the OMD, NDFD and ME. Addition of AMZ linearly increased (P < 0.05) the asymptotic gas production, but GP linear increased (P < 0.05) only at the 6-hour and 12-hour time points. The rate of gas production and the lag time decreased linearly (P < 0.05) in response to increasing AMZ addition. Inclusion of PRO did not affect (P > 0.05) asymptotic gas production, but there was quadratic effect (P < 0.05) on the rate of gas production, the lag time, and the GP at the 6-hour and 12-hour time points. The OMD, NDFD and ME were not affected by PRO addition. Thus, fibrolytic, amylolytic and proteolytic enzymes are effective in reducing the lag time and increasing the in vitro gas production from Brachiaria Brizantha cv. Marandu forage, and fibrolytic enzymes improve the in vitro fermentation profile.