datasheet1_Effects of Fermented Oat Straw as a Lovastatin Carrier on in vitro Methane Production and Rumen Microbiota.docx

To date, there is an urgent need for implementing practical strategies to reduce CH4 emissions from ruminants. Lovastatin (Lv) is a specific inhibitor of methanogenic archaea. Due to the high cost of pure Lv, solid-state fermentation might be an economical bioprocess to produce Lv and facilitate its use in ruminant nutrition. The goal of this work was to assess the effects of supplementing fermented oat straw as a lovastatin carrier (FOS) to a high-grain ration on in vitro CH4 inhibition and rumen microbiota in beef cattle. The experimental design of in vitro rumen fermentation was completely randomized with four concentrations of Lv in the diet mixture. The supplementation with FOS to give Lv concentration of 100 and 150 mg L−1 in the ruminal fermentation medium significantly inhibited methanogenesis at similar levels. This suggested that less than 20% of FOS was required in the ration to achieve up to 38% of CH4 mitigation without affecting the chemical composition and nutritional value of the ration. Short-chain fatty acid (SCFA) production and profile showed that only the treatments with Lv at 100 and 150 mg L−1 decreased the concentration of total SCFAs; the molar ratio of propionate significantly increased with respect to that of the control. Treatment with Lv at 150 mg L−1 did not result in significant differences in the alpha and beta diversity indices compared to the control. However, significant changes in the relative abundance of some microorganisms were detected, such as an increase in Ruminococcus and a decrease in Prevotella. The predominant 99%+ MA in all controls, treatment, and inocula samples belonged to the Methanobrevibacter genus and very small (negligible) unclassified Methanobacterium genus (Euryarchaeota phylum). Interestingly, the reduction of relative abundance of MA was 39.17%, very close to the percent reduction of CH4 production, 38%. Our data showed that there was a parallel and similar percent decrease of both CH4 production and relative abundance of the predominant MA in our experiment, although the statistical significance was not complete. Finally, our results hold promise for significantly decreasing ruminal CH4 by 38%. Thus, our work is one step toward the sustainable management of the livestock sector.

截至目前，亟需制定切实可行的策略以降低反刍动物的甲烷（CH4）排放。洛伐他汀（Lovastatin，Lv）是一种特异性产甲烷古菌（methanogenic archaea）抑制剂。由于纯洛伐他汀成本高昂，固态发酵（solid-state fermentation）或许是一种经济可行的生物工艺，可用于生产洛伐他汀并推动其在反刍动物营养中的应用。本研究旨在评估以发酵燕麦秸秆（fermented oat straw，FOS）作为洛伐他汀载体添加到高精粮日粮中，对肉牛体外（in vitro）瘤胃发酵甲烷抑制效果及瘤胃微生物群的影响。

体外瘤胃发酵实验采用完全随机设计，设置日粮混合物中四种不同的洛伐他汀浓度。在瘤胃发酵培养基中添加FOS以使洛伐他汀浓度达到100和150 mg·L⁻¹时，可显著抑制产甲烷作用，且抑制效果相当。这表明，当日粮中FOS添加量低于20%时，即可实现最高38%的甲烷减排，且不会影响日粮的化学成分与营养价值。

短链脂肪酸（short-chain fatty acid，SCFA）的产量与组成分析显示，仅当洛伐他汀浓度为100和150 mg·L⁻¹时，总短链脂肪酸浓度才会降低；与对照组相比，丙酸的摩尔占比显著升高。当洛伐他汀浓度为150 mg·L⁻¹时，与对照组相比，α多样性与β多样性指数并无显著差异。但检测到部分微生物的相对丰度发生显著变化，例如瘤胃球菌属（Ruminococcus）相对丰度升高，普雷沃氏菌属（Prevotella）相对丰度降低。

所有对照组、处理组及接种物样本中占比99%以上的产甲烷古菌（methanogenic archaea，MA）均隶属于甲烷短杆菌属（Methanobrevibacter），未分类的甲烷杆菌属（Methanobacterium）（广古菌门Euryarchaeota）占比极低（可忽略不计）。值得注意的是，产甲烷古菌的相对丰度降低了39.17%，与甲烷产量38%的降幅极为接近。本研究数据表明，尽管统计学显著性尚未完全达成，但本实验中甲烷产量与优势产甲烷古菌相对丰度均呈现出相近的百分比降幅。最终，本研究结果证实可将瘤胃甲烷产量降低38%，这为畜牧业的可持续管理迈出了重要一步。