The results showed that pre-treatment with PCE for 7 days significantly reduced the bacterial load and the levels of inflammatory factors (IL-6, IL-1β, TNF-α, MPO) in the mammary gland and blood induced by S. aureus, improved the pathological damage of the mammary gland tissue, and alleviated the occurrence of mastitis in mice by regulating the intestinal microbiota. This evidence concerns the gene MPO and mastitis.