Methane emissions from sheep fed fermented or non-fermented total mixed ration containing whole-crop rice and rice bran

Abstract

The effects of ensiling a total mixed ration (TMR) were compared to those of a control TMR whole-crop rice (WCR) ensiled separately and mixed with other ingredients before feeding. Nutritive value, nitrogen balance, ruminal fermentation and the methane production of sheep were evaluated. Four Suffolk sheep (49.5 ± 3.2 kg) were used in a 2 (treatment) × 2 (period) cross-over design experiment. Experimental treatments were control (not fermented) TMR and fermented TMR (FTMR). Each TMR contained WCR, a compound feed, a vitamin–mineral supplement, dried beet pulp and rice bran in a ratio of 300:250:15:135:300, respectively, on a dry matter basis. The lactic acid contents of the control TMR and FTMR were 5.5 and 73.4 g/kg, respectively. Apparent digestibility of crude protein, ether extract, acid detergent fibre and gross energy was higher for FTMR, which also had higher digestible crude protein and digestible energy concentrations than the control TMR. There were no differences in ruminal pH by TMR type before feeding or 4 h after feeding, although pH was higher ( P=0.0039) in FTMR 2 h after feeding. Total volatile fatty acid and NH 3-N was higher and butyric acid was lower for FTMR 2 and 4 h after feeding, whereas propionic acid was higher only 2 h after feeding. FTMR decreased ( P=0.0001) daily methane emissions and energy lost as methane production. These results show that FTMR increases digestibility and decreases ruminal methane emissions and energy loss compared to non-fermented TMR, and that the depression effect of FTMR on methane emission can contribute to the conversion of lactic acid to propionic acid in the rumen.