瘤胃内溶解态和气体态氢动态平衡的生物数学机制及其调控

The hydrogen (H2) is generated during the production of volatile fatty acids (VFA) after degradation of feed by ruminal mocrobes, and is an important substrate for methanogens to produce methane. Manuplating H2 generation and consumption is helpful not only to optimize the VFA profile, but also to decrease methane emissions. The H2 exsists in two forms of dissolved and gasous H2, and only the form of dissolved H2 is avaiable for the ultilization of methanogens. The gasous H2 is formed, when dissolved H2 is released from liquid into air space in the rumen. The dynamic of H2 balance is very complex, because of the generation, consumption and transfermation of H2 in the rumen. In the present project, different substrates and methanogens inhibitors will be employed to generate different types of H2 balance in in vitro ruminal fermentaion by manipulating the H2 generation and consumption, then we will investigate the relationship between two H2 forms and methane (methanogens), reveal the biochemistrical pathways and microbial methanisms druing the H2 generation and consumption. The LE models will be used to estimate the H2 generation, consumption and conversion, and then reveal the relationship between the dissloved and gasous H2. Furthermore, The animal trial will be performed to verify the biological mechanisms, manipulations and accurancy of prediction of H2 generation and consumption tested through in vitro. The results could be provide scientific proof for optimizing the VFA profile, improving the energy efficiency of feedstuffs and mitigating methane emssions in the ruminants.

瘤胃微生物在降解饲料生成挥发性脂肪酸(VFA)过程中伴随氢气产生，而氢气是甲烷菌合成甲烷的重要前体物；调控瘤胃内氢气生成与消耗不仅可优化VFA组成且可减少甲烷排放。瘤胃内氢气包括溶解态和气体态两种，其中气态氢是由溶解态氢释放到未被瘤胃液充盈的背囊空间所形成，且只有溶解态氢可被产甲烷菌直接利用；两种形态氢气的生成、消耗与转化的动态平衡关系复杂。本项目选用不同生氢能力饲料，体外模拟瘤胃发酵，构建生氢过程差异明显的动态平衡状态，研究两种形态氢气与VFA、甲烷菌数量及种群间的关系，通过甲烷生成抑制剂构建耗氢过程差异明显的动态平衡状态，揭示氢气生成和消耗的生物化学路径和微生物机制；利用前期LE系列模型估算氢气生成与消耗，揭示两种形态氢气间的转化关系。通过动物试验，在体内验证两种形态氢气生成、消耗和转化机制、调控机理及模型估算精度。旨为优化瘤胃发酵模式、提高饲料能量利用效率和减少甲烷排放提供科学依据。

项目背景：氢分子是瘤胃内碳水化物降解生成挥发性脂肪酸产生，最终被甲烷菌代谢生成甲烷。瘤胃内氢分子以溶解态氢(dH2) 和气体态氢（gH2）两种形态存在，且只有溶解态氢与瘤胃微生物接触，具有生物学功能。根据大气平衡溶解原理中的亨利定律，溶解态和气态氢气是可以相互转换的。但是，由于瘤胃液种颗粒物较多且物理生物组成复杂，dH2和gH2通常不能简单地通过亨利定律来转换，两种形态氢的生成、消耗与转化的动态平衡关系复杂。.研究内容：1）饲料生氢过程与dH2和gH2动态平衡的关系；2）调控耗氢过程研究dH2和gH2动态平衡关系；3）体内试验验证不同反刍动物瘤胃内dH2和gH2动态平衡关系。.重要结果：瘤胃发酵8种生氢饲料结果表明：dH2与发酵瓶顶端gH2不存在强相关关系，但与甲烷产量成强正相关，同乙丙比和挥发性脂肪酸生氢效率成强负相关关系。甲烷抑制氢消耗结果显示：甲烷抑制剂改变了氢平衡，促进瘤胃内氢累积，显著降低了己糖发酵、氢产生和消耗。奶牛不同部位实验结果显示：瘘管和口腔胃管采集瘤胃液的dH2浓度同溶解甲烷呈强正相关，同乙丙比和挥发性脂肪酸生氢效率成强负相关关系。高原地区藏绵羊不同碳水化合物来源的饲养试验显示：瘤胃内dH2呈超饱和状态，dH2同溶解态氢饱和系数和溶解甲烷呈强正相关，同乙酸摩尔比例呈强负相关关系。山羊加氢（添加镁）试验证明：瘤胃内dH2升高抑制挥发性脂肪酸生成，减少乙丙比和真菌拷贝数，增加了丙酸摩尔比例、甲烷菌数量和胃肠道甲烷排放量。.关键数据：率先获取了奶牛、山羊和藏绵羊三种反刍动物瘤胃内dH2和gH2数据，建立了瘤胃内溶解气体饱和系数的计算方法和数据，还获取了瘤胃内两种形态氢相互关系及模型，及其同瘤胃发酵模式、甲烷生成和关键瘤胃微生物种群的关系。.科学意义：发现了瘤胃内dH2的超饱和状态，dH2浓度不能通过gH2浓度来预测，强化直接测定瘤胃内dH2浓度的必要性，形成了dH2浓度具有影响瘤胃发酵模式和甲烷生成相关生物学功能的重要观点。