白藜芦醇调控反刍动物甲烷排放的机理研究

Methane has been shown to be one of the important anthropogenic greenhouse gases. The main source of methane in animal husbandry is derived from ruminant industry. Plant extracts have been a research hot spot in methane manipulation in recent years. Our previous study showed that resveratrol could effectively reduce methane emission by sheep. In the proposed project resveratrol is selected as the representative plant extract. Initially, in vitro study was conducted to study the effect of substrate type and resveratrol dosage on methane output. By measuring the concentration of volatile fatty acids as well as hydrogen, and the abundance of methanogen at family and genera level based on mcrA gene, the difference in the mechanism of methane manipulation by resveratrol in different substrate type can be illustrated. Then a feeding trial to observe the manipulation of methane emission by resveratrol and continuously determine the dynamic change of ruminal fermentation parameters and quantification of microbial flora (total methanogen, protozoan, cellulolytic bacteria), with an aim to investigate the regulatory pathway of manipulation of methane emission by resveratrol in mutton sheep under different dietary regime. Furthermore, the high-throughput sequencing technique is applied to study the changes in the abundance of methanogenesis-related microbes at family and genus level, with an aim to deeply illustrate the differences in mechanisms by which resveratrol manipulate methane emission by ruminants, and finally provide the theoretic support for the reasonable utilization of plant extracts.

甲烷是重要的温室气体之一，畜牧养殖业的甲烷主要来自反刍动物，植物提取物成为近年来甲烷调控研究的热点之一。我们前期研究表明白藜芦醇能够有效降低绵羊甲烷排放，但其机理并不明确。本项目拟以白藜芦醇为研究对象，首先开展体外试验研究，明确底物类型和白藜芦醇添加剂量对甲烷产量的影响，测定底物挥发性脂肪酸及氢离子浓度，基于mcrA基因测定产甲烷菌在各科属水平上的丰度，初步阐明不同底物类型下白藜芦醇调控甲烷产生的差异机制，并确定适宜的添加剂量。随后开展动物试验，通过连续测定瘤胃发酵参数，明确白藜芦醇对瘤胃生理功能的调控作用；利用高通量测序技术从科属水平研究与甲烷生成密切相关的微生物丰度变化情况，明确白藜芦醇调控反刍动物瘤胃甲烷合成的微生物学机制，为合理高效利用植物提取物提供重要依据。

畜牧养殖业超过95%的甲烷排放主要来自反刍动物，排放量约8000万吨。传统的甲烷排放调控剂包括莫能菌素等抗生素，植物提取物成为近年来甲烷调控研究的热点，与莫能菌素相比，瘤胃微生物对植物提取物产生的抗药性更低，且使用后的动物产品中基本无残留。多酚化合物是存在范围最普遍的一种植物提取物，其中具有代表性的单宁在体外能够有效降低甲烷产量，白藜芦醇（resveratrol，RSV）是一种非黄酮类多酚，主要存在于葡萄、虎杖、花生等植物中具有抗真菌、病毒以及抗氧化特性。我们前期以绵羊为试验动物开展的研究表明，白藜芦醇能够有效降低甲烷排放，且并未对肉羊生产性能造成副面作用，因此开展本项目，深入探索白藜芦醇调控反刍动物甲烷排放的途径及微生物机理。研究结果表明，发酵底物中添加高水平RSV可以有效降低甲烷产量、促进丙酸发酵，这与革兰氏阳性菌（纤维杆菌和放线菌门）相对丰度降低、瘤胃环境中代谢产生大量DH-RSV导致的甲烷合成底物减少有关；同时，高添加水平的RSV通过抑制瘤胃中以普雷沃氏菌为代表的淀粉、蛋白降解菌，抑制了发酵底物在瘤胃的降解和发酵；日粮中添加RSV能够通过抑制产甲烷短杆菌属（Methanobrevibacter）的丰度，降低肉羊甲烷的排放。本项目的开展为合理利用白藜芦醇调控反刍动物甲烷排放提供了应用思路，确定了适宜的添加剂量，以及在高精料和高粗料条件下效果的差异，为实际应用提供了参考，可直接用于生产。