The efficacy of methane (CH₄) suppression using medium-chain fatty acids (MCFA) remains inconclusive, despite a number of studies on this topic are available. We thus carried out a meta-analysis to integrate the published data on different concentrations and types of MCFA such as lauric acid and myristic acid, which investigated ruminal methanogenesis and fermentation in in vitro and in vivo experiments. In vitro MCFA sources were classified either as pure MCFA (lauric acid, myristic acid and their combinations) or as natural MCFA-rich oils (canola oil enriched with lauric acids, coconut oil, krabok oil and palm kernel oil). The MCFA sources used in the in vivo studies were coconut oil, lauric acid, myristic acid and the combination of lauric and myristic acids. A total of 41 studies (20 in vitro and 21 in vivo studies) were compiled in our database, which included the data on CH₄ emission, digestibility, ruminal fermentation products and microbial populations. The results showed that the amount of CH₄ production per unit of digested organic matter decreased linearly under in vitro conditions (p < .01) and tended to decrease quadratically under in vivo conditions (p < .07) with increasing doses of MCFA. Populations of protozoa (p < .01) in both in vitro and in vivo responded negatively in a linear manner, whereas Archaea population diminished quadratically (p = .04) only in the in vitro conditions with increasing doses of MCFA. Increasing dietary MCFA concentrations also reduced the fibre digestibility linearly (p < .05) in both in vitro and in vivo conditions. CH₄ production for different sources of MCFA decreased in following order: coconut oil > lauric acid > myristic acid > mixed lauric and myristic acids > palm kernel oil > canola oil enriched with lauric acids > krabok oil. It can be concluded that the effect of MCFA on ruminal methanogenesis depends on the amount and type of MCFA.

中文翻译：

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日粮中链脂肪酸对体外和体内瘤胃产甲烷和发酵的影响：荟萃分析

甲烷（CH ₄) 使用中链脂肪酸 (MCFA) 进行抑制仍然没有定论，尽管对此主题进行了大量研究。因此，我们进行了一项荟萃分析，以整合有关不同浓度和类型的 MCFA（如月桂酸和肉豆蔻酸）的已发表数据，在体外和体内实验中研究了瘤胃产甲烷和发酵。体外 MCFA 来源分为纯 MCFA（月桂酸、肉豆蔻酸及其组合）或富含天然 MCFA 的油（富含月桂酸、椰子油、克拉博克油和棕榈仁油的菜籽油）。体内研究中使用的 MCFA 来源是椰子油、月桂酸、肉豆蔻酸以及月桂酸和肉豆蔻酸的组合。我们的数据库中总共汇编了 41 项研究（20 项体外研究和 21 项体内研究），₄排放物、消化率、瘤胃发酵产物和微生物种群。结果表明，随着 MCFA 剂量的增加，每单位消化有机质的 CH ₄产量在体外条件下呈线性下降 ( p < .01)，在体内条件下呈二次下降趋势 ( p < .07)。体外和体内的原生动物种群 ( p < .01) 都以线性方式呈负面反应，而古细菌种群仅在体外条件下随着 MCFA 剂量的增加呈二次减少 ( p = .04)。增加膳食 MCFA 浓度也线性降低纤维消化率（p< .05) 在体外和体内条件下。不同来源的MCFA的CH ₄产量按以下顺序下降：椰子油>月桂酸>肉豆蔻酸>混合月桂酸和肉豆蔻酸>棕榈仁油>富含月桂酸的菜籽油>克拉博克油。可以得出结论，MCFA对瘤胃产甲烷的影响取决于MCFA的数量和类型。