Oleic and linoleic acids alter fermentation characteristics, methane and fatty acid isomers production during in vitro incubation with mixed ruminal microbes

This study was conducted to investigate the effects of oleic acid (OA) and linoleic acid (LA) supplementation on in vitro fermentation characteristics, methane and hydrogen production, and fatty acid isomer production of Leymus chinensis using in vitro gas production technique. The experiment was consisted of three treatments: control (CON), OA (50 mg OA/500 mg substrate, dry matter basis) and LA (50 mg LA/500 mg substrate, dry matter basis). OA supplementation of 50 mg increased (P<0.001), but 50 mg of LA supplementation decreased (P<0.001) in vitro total gas production of Leymus chinensis. When compared to CON, OA and LA supplementation decreased (P<0.001) methane production, but increased (P<0.001) total hydrogen production of Leymus chinensis. The unsaturated fatty acids (OA and LA) supplementation did not affect (P>0.05) in vitro rumen fermentation parameters, including pH, and the concentrations of ammonia-N, acetate, propionate, butyrate, valerate and total VFA of incubation fluids but decreased (P<0.001) the ratio of acetate to propionate at 24 h of in vitro incubation. The LA supplementation increased (P<0.001) the concentrations of C18:1 (trans 11) at 24 h and 48 h, and C18:2 (c9t11-CLA) at 24 h when compared to CON or OA. The LA supplementation increased (P<0.001) total n-6 PUFA concentration at 24 h, but OA supplementation decreased (P < 0.05) the concentration of total n-3 PUFA at 48 h when compared to CON. The current results implied that unsaturated fatty acid supplementation can suppress methane release and alter biohydrogenation of fatty acids in the rumen.