PSVIII-8 Effect of Lactobacillus Casei Zhang on E. coli induced injury of blood and milk barrier in dairy cow

Abstract Bovine mastitis is one of the major diseases which directly affects the milk production performance and it causes huge economic losses in the dairy industry. Bacterial infection is the main risk factor of bovine mastitis and the antibiotic therapy is the primary choice to control the disease. However, persistence use of antibiotic increases the incidence of bacterial resistance and traces of antibiotic residues in animal products. Lactobacillus casei Zhang is one of the probiotics with multiple biological functions, which has certain bacteriostatic effect on pathogenic microorganism. The purpose of this study was to explore the effect of Lactobacillus casei Zhang (L. casei Zhang) on the prevention of E. coli-induced milk-blood barrier damage. Bovine mammary epithelial cells (BMECs) were used to establish a milk-blood model and Control group (PBS), E. coli group, and L. casei Zhang pretreatment plus E. coli group were set up respectively. The results showed that: L. casei Zhang could significantly reduce the increase of LDH release caused by E. coli treatment (P< 0.05). And it can also significantly reduce the decrease of transmembrane resistance of monolayer cells caused by E. coli treatment (P< 0.05). In addition, L. casei Zhang could significantly reduce the expression of tight junction proteins ZO-1, Claudin-1, Claudin-4 and Occludin (P < 0.05). In conclusion, L. casei Zhang could effectively improve the damage of the blood-milk barrier caused by E. coli and could protect BMECs during bacterial infection.