基于“挑食行为-瘤胃微生物区系-瘤胃上皮功能”路径研究奶牛SARA易感性差异的发生机制

奶牛亚急性瘤胃酸中毒(SARA)是一种因瘤胃pH值过低而引起的营养代谢病。资料显示，奶牛对SARA的易感性具有明显的个体差异；然而致SARA易感性差异发生的生物学基础尚不清楚，推测与奶牛挑食行为影响了瘤胃VFA生成和瘤胃上皮对VFA的吸收功能有关，但确切机制不明。本项目拟构建挑食行为诱发奶牛SARA易感性差异研究模型，进而探讨挑食行为对奶牛营养物质摄入、瘤胃发酵活力和瘤胃上皮吸收VFA功能的影响规律，明确上述影响与瘤胃pH变化间的内在联系；在此基础上，项目拟应用宏转录组学等技术，解析挑食行为诱发奶牛瘤胃微生物群落稳态改变及其影响瘤胃VFA产生的机制，明晰挑食行为诱发的瘤胃pH和VFA组成变化影响瘤胃上皮吸收VFA功能的机理，从而揭示“挑食行为-瘤胃微生物区系-瘤胃上皮功能”路径在SARA易感性差异发生中的作用与机制。项目有望在瘤胃功能基础研究方面产生原始创新，并对奶牛健康养殖有重要意义。

Subacute ruminal acidosis (SARA) is a nutritional metabolic disease which was caused by low ruminal pH in dairy cattle. Previous studies showed that there is an inter-animal variation in the susceptibility of SARA for dairy cattle. However, the mechanism underlying the inter-animal variation in susceptibility to SARA in dairy cattle is not clear, and it might be related to the alternation in ruminal volatile fatty acid (VFA) production and VFA remove induced by feed sorting, but the detailed mechanism is not clear. In this project, firstly, we will establish a cow model to explore the inter-animal variation in susceptibility to SARA induced by feed sorting. Based on this model, we will evaluate the effect of feed sorting on the nutrients intake, ruminal fermentation activity, and absorption of ruminal VFA by ruminal epithelium, and clarify the relationship between these results and the changes in ruminal pH. Additionally, this project will apply the techniques such as metatranscriptomics to explore the ruminal microbial mechanism underlying the effect of feed sorting on the changes in rumen homostasis and ruminal VFA production. Further, this project will investigate the effect of alternation in ruminal pH and VFA composition induced by feed sorting on the function of VFA absorption through ruminal epithelium. The results from this project will reveal the role of feed sorting, ruminal microbiota, and function of ruminal epithelium in causing the inter-animal variation in susceptibility to SARA and its underlying mechanism in dairy cattle. Generally, this project is expected to generate original innovation in the field of ruminal function research, and these findings from this project can be applied in health production of dairy cows.