采食行为与瘤胃上皮功能对湖羊SARA变异性的影响及机制研究

Sub acute ruminal acidosis (SARA) is a prevalent nutritional metabolic disorder found in meat sheep production. Previous studies indicated that huge varations exist in the extent and risk of SARA among sheep fed identical diets. However, the possible mechanisms contributed to these variations have not been studied. In the present sutdy, we foucus on the SARA susceptibility in hu sheep, and hypothesis that both feeding behaviors and ruminal epithelium transportation or metabolism activities for volatile fatty acids (VFA) are contribute to the different SARA susceptibility in sheep. Firstly, we indend to evaluate the risk of SARA and its susceptibility in sheep herd. And the sheep with highest and lowest ruminal pH will be classified as tolerant and susceptible to SARA, respectively. The feeding behavior and mRNA expresstion relate to VFA absorption and metabolism are determined, which to demostrate the cause of different SARA susceptibility in sheep. Finally, we use multi-platform metagenomic analyses and Real time PCR technologies to establish the relaitonship of ruminal bacteria and SARA susceptibility of sheep. All these experiments will provide new insight into the mechanism of SARA as well as scientific basis for the improvement of rumen health and efficiency in sheep prodution.

亚急性瘤胃酸中毒（SARA）是肉羊生产过程中常见的营养代谢疾病，研究发现，采食相同日粮的反刍动物，个体间SARA发生风险及严重程度存在明显的差异，但导致这种差异的机制并不清楚。因此，本项目以绵羊个体SARA耐受性差异的角度为切入点，假设“绵羊采食反刍行为与瘤胃上皮功能的差异是导致个体间SARA耐受性变异的主要因素”。项目以湖羊为研究对象，首先，系统评估其育肥阶段SARA风险与群体变异性；根据群体瘤胃pH筛选SARA耐受和易感个体，通过检测其采食反刍行为与瘤胃上皮挥发性脂肪酸转运与代谢相关基因表达情况，揭示引起绵羊SARA耐受性差异的机制；最后，借助宏基因组测序技术及荧光定量PCR等手段，阐明湖羊SARA易感性与瘤胃微生物多样性之间的内在关联机制。上述研究为揭示SARA发生机制提供新的视野，并为改善绵羊瘤胃健康提供理论依据。

亚急性瘤胃酸中毒（SARA）是绵羊育肥生产中常见的营养代谢性疾病，对绵羊机体健康和生产性能均造成不利影响。研究发现，采食相同饲料的绵羊，其SARA的风险存在差异，这为生产中预防和缓解SARA风险造成困难，并且SARA变异性原因尚不明确。本研究通过饲喂120只绵羊相同的育肥饲料，通过分析瘤胃发酵参数、瘤胃微生物区系、上皮吸收和代谢功能基因的表达情况，分析导致SARA变异性的因素。研究结果表明，采食相同饲料的育肥绵羊，其瘤胃pH、VFA组成和微生物组成变异性较大，其中采食后2-4 h瘤胃pH与pH敏感微生物丰度及瘤胃发酵参数不相关，而4种瘤胃pH敏感的微生物之间密切相关，表明2-4 h瘤胃pH并不是判断瘤胃动态pH和SARA风险的敏感参数。在此基础上，研究利用4种pH敏感性微生物用于判断绵羊SARA风险，发现低SARA风险个体和低SARA风险个体其瘤胃微生物多样性差异显著，且厚壁菌门、拟杆菌门丰度差异显著，但二者在瘤胃上皮VFA吸收和代谢功能基因表达量无显著差异，上述研究结果表明，不同SARA变异性绵羊与瘤胃微生物区系的变化有关，而与瘤胃上皮吸收和代谢功能无关，本研究为揭示绵羊SARA的变异性机理提供理论依据。