反刍动物与单胃草食动物甲烷排放差异的微生物机制研究

Inhibition of methane emission has beneficial effects on both environment and animal production. Scientists have developed many approaches to reduce methane emission. There are advantages and disadvantages for different methods, most of which can reduce methane emission but decrease fiber digestion together. Monogastric herbivores have similar ability to digest fiber with ruminants, but produce much lower methane. There may exist the different microbiota for hydrogen metabolism in the gastrointestinal tracts. Based on the results from our previous experiments, the Hu sheep and Japanese White Rabbits will be used in this project to study the microbiological mechanisms for the difference in methane emission between ruminants and monogastric herbivores. The hydrogen utilization ability will be estimated in the sheep and rabbits offered hay only in order to outline the relationship between hydrogen metabolism and methane production. By using transcriptomics and metabolomics methodologies, the function of uncultured microorganisms, the microbial metabolites will be analyzed to elucidate if there are different pathways of hydrogen metabolism between sheep and rabbits. The importance of hydrogen-utilizers in the methane production between sheep and rabbits will be estimated by transcriptomics with the enrichment of hydrogen-utilizers and microbiota analysis. The output of this project will contribute to clarify for the difference in methane emission between ruminants and monogastric herbivores.

降低反刍动物甲烷排放对环境和动物生产具有双重意义。调控反刍动物甲烷排放的手段多样，各存利弊，多不能兼顾纤维消化与甲烷减排。单胃草食动物与反刍动物具有同等的饲料消化力，但甲烷排放量不同，两者消化道氢代谢微生物差异可能是其甲烷排放量不同的根本原因。基于前期工作，本项目拟选取湖羊和日本大耳白兔分别作为反刍动物和单胃草食动物代表，在仅饲喂青干草的情况下，研究湖羊瘤胃和兔盲肠微生物产氢能力和氢利用能力差异，论证氢代谢能力差异是导致反刍动物与单胃草食动物甲烷排放量差异的核心；借助转录组学和代谢组学研究湖羊和兔消化道微生物功能及代谢产物异同，探讨湖羊和兔是否存在不同的氢代谢优势途径，论证未培养微生物在纤维消化过程所起的作用；结合氢利用菌富集、菌群多样性分析，发掘未知的氢利用菌，探讨氢利用菌在湖羊和兔甲烷排放量差异中的作用。在一定程度上揭示反刍动物与单胃草食动物甲烷排放量差异的微生物机制。

降低反刍动物甲烷排放对环境和动物生产具有双重意义。调控反刍动物甲烷排放的手段多样，各存利弊，多不能兼顾纤维消化与甲烷减排。单胃草食动物与反刍动物具有同等的饲料消化力，但甲烷排放量不同，两者消化道氢代谢微生物差异可能是其甲烷排放量不同的根本原因。基于前期工作，本项目选取6只成年瘘管湖羊和18只成年新西兰白兔分别作为反刍动物和单胃草食动物代表，在仅饲喂苜蓿的情况下，利用呼吸测热室测定了两物种甲烷和二氧化碳排放量；测定两物种的干物质采食量、干物质消化率，并在此基础上，基于16SrDNA高通过测序和荧光定量技术分析消化道微生物数量和区系与甲烷排放量间关系，在宏基因组、宏转录组和代谢组层面揭示湖羊和兔消化道微生物组成和代谢功能差异。研究发现湖羊瘤胃纤维降解以产氢微生物Butyrivibrio、 Succiniclastium、Mogibacterium、Prevotella和 Christensenellaceae为主，而兔盲肠纤维降解菌以非产氢微生物Bacteroides为主；而且兔盲肠产乙酸菌数量高于湖羊瘤胃，RCC产甲烷菌和非RCC产甲烷菌数量均低于湖羊瘤胃。无论是湖羊瘤胃还是兔盲肠，厚壁菌门（Firmicutes）和拟杆菌门（Bacteriodetes）均是碳水化合物代谢酶的主要贡献者；兔盲肠微生物表达的糖苷水解酶基因高于湖羊瘤胃微生物，但其纤维粘附结构域显著低于湖羊瘤胃微生物；瘤胃拟杆菌门特化出更丰富的PUL结构提高酶的降解能力。Blautia（产乙酸）、Oscillospira（产丁酸）、Bacteroides（产琥珀酸）等是潜在的降甲烷靶向菌。上述研究在一定程度上揭示了反刍动物与单胃草食动物甲烷排放量差异的微生物机制，已发表SCI论文1篇、投稿SCI论文1篇、国内外会议论文9篇、授权专利2项、申请发明专利9项，培养研究生10名。