Effect of raw rice bran supplementation on rumen methanogen population density and in vitro rumen fermentation

Abstract

AbstractThe effect of raw rice bran supplementation on in vitro rumen methane production, short‐chain fatty acid (SCFA) production and profile, and the population density of methanogenic archaea was studied using batch cultures of rumen fluid. The experimental batch culture conditions were as follows: a control group containing a substrate without supplements; substrates supplemented with 5, 10 or 15% raw rice bran; and a culture treated with an antimethanogenic agent, bromoethanesulfonate (BES), as a positive control. The methanogen population density in the cultures was determined by methanogen‐specific real‐time polymerase chain reaction (PCR) assay. The BES treatment completely inhibited methane production. Supplementation with 10% raw rice bran inhibited methane production by 18% after a 24‐h incubation (P > 0.05). No significant difference in total SCFA levels was observed between all the treatments, although the SCFA profiles were altered. Whereas the proportion of butyrate increased significantly, the proportion of propionate decreased significantly in the 10% rice bran treatment (P < 0.05). Only 10% raw rice bran supplementation significantly reduced the methanogen population density by 25% compared with the control after the 24‐h incubation (P < 0.05). The results showed that supplementing the substrate with 10% raw rice bran affects SCFA profiles and methanogen population density in rumen fermentation in vitro.