Total gas production by the diets of R:C ratio of 70:30 added with nitrate and fumarate has been presented in Table 2. Total gas production increased for CAC vs. CAKC, CAKC vs. CC, and CC vs. CKC, when no additive was added. With the addition of nitrate, total gas production also followed same trends among the diets. Total gas production was higher for CAC than CC and CAKC, and CKC produced lowest gas when nitrate was added to the diets. Nitrate decreased total gas production than control (without any additive) and fumarate. Gas production was greater in fumarate than control for the CC and CAKC diets, but was similar for CA and CKC diets.