Altering Methane Emission, Fatty Acid Composition, and Microbial Profile during In Vitro Ruminant Fermentation by Manipulating Dietary Fatty Acid Ratios

Abstract

This study evaluated the effects of different dietary n-6/n-3 polyunsaturated fatty acid (PUFA) ratios on in vitro ruminant fermentation. Methane production, fatty acid composition, and microbial profiles were compared after the in vitro fermentation of rumen fluid collected from cows that had been fed isoenergetic and isoproteic experimental diets at three different n-6/n-3 ratios: 3.04 (HN6, high n-6 source), 2.03 (MN6, medium n-6 source), and 0.8 (LN6, low n-6 source). The fermented rumen fluid pH and total volatile fatty acid (VFA) levels were significantly decreased (p < 0.05) in the HN6 group as compared with those in the MN6 and LN6 groups. Additionally, the HN6 group produced a significantly lower (p < 0.05) proportion of methane than the MN6 group during in vitro fermentation. The MN6 and LN6 groups had significantly increased (p < 0.05) levels of C18:2n6 and C18:3n3 in the fermented rumen fluid, respectively, as compared with the HN6 group. The Chao 1 diversity index value was lower (p < 0.05) in the HN6 group than in the MN6 and LN6 groups. The observed species richness was significantly lower (p < 0.05) in the HN6 group than in the MN6 group. The reduced relative abundances of Lachnospiraceae UCG-006 and Selenomonas in the HN6 group resulted in lower pH and VFA levels (i.e., acetate, propionate, butyrate, and total VFA) during in vitro fermentation. Furthermore, n-6 and n-3 PUFAs were toxic to Butyrivibrio_2 growth, resulting in high levels of incomplete biohydrogenation. Taken together, the study findings suggest that supplementation of high-forage diets with high levels of n-6 PUFAs could reduce methane emissions, whereas both VFA concentration and pH are reduced.

In vitro ruminal fermentation, core nutrient, fatty acids and mineral matter of pennyroyal (Mentha pulegium L.) herbage at different phenological stages

“…Low methane production at the seed bulking stage may come forth less in vitro fermentation (low total gas production) due to related to the increased lignin hemicellulose complex of the plant (Terrett & Dupree, 2019 ). Besides, low methane production at the seed bulking stage can be connected to the anti‐methanogenic property of the high level of oil content and ω−3 and ω−6 fatty acids at the seed bulking stage (Yilmaz and Kara, 2022b ; Sun et al., 2022 ).…”

Effect of Unsaturated Fatty Acid Ratio In Vitro on Rumen Fermentation, Methane Concentration, and Microbial Profile

“…Previous studies have shown that the addition of fat to dairy cows' diets produces various changes in rumen fermentation, which are closely related to FA composition [17,31,32]. It has been reported [6] that adding excessive fat to the diet of dairy cows inhibits rumen fermentation, especially the addition of UFA, which has a more obvious inhibitory effect on rumen fermentation.…”

“…As described by Sun et al [17] and Cui et al [18], gas chromatography (Agilent 6890N, Agilent Technologies, Inc., Beijing, China) determined the VFA concentrations of incubation fluid and the gas composition (CO 2 and CH 4 ) in gas samples. NH 3 -N concentrations in incubation fluid were measured by spectrophotometry according to Verdouw et al [19].…”

Effects of yeast culture on in vitro ruminal fermentation and microbial community of high concentrate diet in sheep

“…Moreover, MCP content was analyzed following the method described by Makkar et al ( 1982 ). The gas chromatography (JC-7890, Juchuang Group Co., Ltd., Qingdao, Shandong, China) was utilized to analyze the VFA concentrations, including acetate, propionate, butyrate, isovalerate and valerate (Sun et al 2022 ). The non-glucogenic-to-glucogenic acids (NGR) ratio was calculated by NGR = (acetate + 2 butyrate + valerate) / (propionate + valerate) (Zhang and Yang 2011 ).…”