A study including two experiments (Exp), was conducted at CanTho University to measure organic matter digestibility and gas production of some supplement feeds to rice straw and Brachiaria mutica. The Exp 1 was a completely randomized design with 6 treatments and 3 replications. The treatments were Brachiaria mutica grass, banana trunk, rice straw, 70% para grass (Brachiaria mutica)+ 30% banana trunk, 70% rice straw + 30% banana trunk, 70% rice straw + 30% Mucana pruriens (%, DM). The Exp 2 was a 2*3 factorial design with 3 replications. Factor 1 was basal feeds (including para grass and straw), while factor 2 was supplements consisting banana trunk, Mucana pruriens and broken rice. The results the Exp 1 showed that the OM digestibility (OMD) at 48 and 72 hours were the highest values for the banana trunk treatment. In Exp 2, gas production at 48 and 72 hours was significantly higher for Para grass (P2 = 0.80. It was concluded that supplementing banana trunk, Mucana pruriens and broken rice to rice straw or Brachiaria mutica grass improved the dietary nutrients and digestibility and gas production.