Abstract: The objective of this study was to evaluate the effects of various feeds using rumen fermentation in inoculum of buffalo and cattle by using the in vitro gas technique. Incubations were carried out using rumen fluid obtained from rumen-fistulated swamp buffalo and cattle during which rice straw was fed on ad libitum as a main feed with minimal amount of concentrate (concentrate mixture: 12% CP and 76% TDN) feeding. The fermentation kinetics from twelve feeds commonly used in ruminant was studied using in vitro gas production technique. Rumen fermentation parameters substrate disappearance and Volatile Fatty Acids (VFA) production were determined after 96 h of incubation. The results revealed that high potentials for gas production were obtained in concentrate, upper-leaf cassava hay, cassava hay, Trichanthera gigantea, lower-leaf cassava hay, Plia fran leaf (Pluchea indica) and were highly degradable in the rumen of both species, especially significantly higher in swamp buffalo than in cattle fluid. However, rumen NH3, VFAs, acetate and acetate to propionate ratio in cattle were higher than in buffalo. However, the propionate production resulted higher in buffalo (p<0.001) than in cattle. Therefore, the results indicate that twelve feeds in total gas production and C3 in buffalo were higher than in cattle liquor accept for rumen NH3-N, total VFAs, C2, C4 and C2: C3 concentrations.