Objective: To evaluate total in vitro gas and methane (CH4) production in different mixtures of Hyparrhenia ruffa (Hr) and Leucaena leucocephala (Ll). Design/methodology/approach: In airtight biodigesters with 200 mL of culture medium, 20 g of the following treatments were incubated by triplicate: T1: 100% Hr, T2: 80% Hr 20% Ll, T3: 60% Hr 40% Ll, T4: 40% Hr 60% Ll; these were inoculated with 20 mL of fresh rumen f luid and incubated at 380.5 °C for 24, 48, 72 and 96 h. The total gas and CH4 production were assessed; the data were analyzed in a completely randomized design. Results: The addition of 20%, 40% and 60% Ll in mixture with Hr decreased the neutral detergent fiber (NDF), acid detergent fiber (ADF), total gas and CH4 production, while the crude protein content increased. Study limitations/implications: In vivo studies are required / by including amounts higher than 20% Ll may improve energy utilization efficiency. Findings/conclusions: Adding more than 20% L. leucocephala in a mixture with H. ruffa decreases total gas and CH4 productio
