In vitro ruminal dry matter digestibility and methane production of fermented total mixed ration containing whole-crop rice and rice bran

Abstract

Three in vitro incubation experiments were conducted to determine the effect of fermented total mixed ration (FTMR) and fresh TMR containing whole-crop rice and rice bran on dry matter (DM) digestibility and methane production in the rumen. In incubation 1, FTMR and fresh TMR were each incubated with neutral culture medium for 2, 4 or 6 h. The FTMR had higher (P < 0.05) DM digestibility but lower (P < 0.05) methane production than fresh TMR. In incubation 2, the two TMR with or without lactic acid (5%, DM basis) were incubated with neutral culture medium for 6 h. Regardless the addition of lactic acid, the FTMR showed higher DM digestibility (P < 0.05) and lower methane production (P < 0.05) than fresh TMR. In incubation 3, the two TMR were each incubated for 6 h in three types of culture medium with pH 7.08, 5.86 or 6.56, respectively. Regardless of the TMR, DM digestibility and methane production decreased with pH declining, when the final pH was 5.62–5.66, the DM digestibility and methane production reached the lowest level, and the propionic acid reached the highest level. These results suggest that FTMR had higher DM digestibility and lower methane production than fresh TMR, and that final pH seemed to contribute to the conversion of lactate to propionate and inhibit methane production in the rumen.