犊牛腹泻发病的本质是致病细菌侵入肠道释放肠毒素而引起。肠道共生菌群定植后黏附在肠壁上避免肠壁与致病菌接触，并共生菌群与肠道免疫系统形成互动，使肠道应对致病菌能力强大。但犊牛肠道共生菌群尚未定植形成保护网络时，如何保护肠道健康和益生菌菌群的定植？项目组发现酸马奶微生物代谢物显著降低被感染致病E. coli小鼠肠道中E. coli的数量，增加乳酸杆菌、双歧杆菌的有效定植和抑制致病菌增殖。据此假设：酸马奶微生物代谢物促进益生菌逃逸抗菌肽建立稳定种群；促进肠道益生菌群与犊牛免疫系统和内分泌系统形成互动，抑制致病菌实现减排。因此本项目拟采用高通量测序、ELISA、流式细胞和试剂盒等生物技术研究“酸马奶微生物代谢物对犊牛肠道微生物组定植及致病菌减排作用机制”阐明酸马奶微生物代谢物在建立犊牛肠道共生益生微生物组、免疫系统和内分泌系统形成互动的作用机制，为寻找抑制肠道致病菌和减排肠道致病菌提供理论依据。

The nature of calf diarrhea incidence is caused by the release of enterotoxin from pathogenic bacteria invasion of intestine. The adhesion of intestinal commensal flora on the intestinal wall after colonization prevents the contact of the pathogens with the intestinal wall, and the commensal bacteria interact with the intestinal immune system and strengthen the ability of intestine to cope with the pathogens. But the calf intestinal commensal flora has not colonize to form a protective network, how to protect the health of intestine and probiotic flora colonization?The project team found that Koumiss microbial metabolites significant reduced the number of intestinal E. coli in the mice infected by pathogenic E. coli infected mouse and increased the effective colonization of lactobacilli and bifidobacteria and suppress the proliferation of pathogenic bacteria. Hypothesizion: Koumiss microbial metabolites promote the escape of probiotics from antimicrobial peptides to establish stable population, and promote the interaction of intestinal probiotics group and immune and endocrine systems of calves and inhibit bacteria to realize pathogen emission. Therefore, the project intends to study themechanism of effect of koumiss microorganism metabolites on calf intestinal microbiome colonization and pathogenic bacteria emission using High-throughput sequencing, ELISA, flow cytometry and biotechnology kits to clarify the mechanisms of effect of Koumiss microbial metabolites in the establishment of the interaction of calf intestinal commensal probiotic microorganism group with immune and endocrine systems, and provide a theoretical basis for looking for the inhibition of intestinal bacteria and emission of intestinal pathogens.