Mammary immune response following intrateat lipopolysaccharide infusion in lactating goats

Mastitis caused by bacterial pathogens entering the teat canal remains a major concern in dairy production. Although many studies have examined the response to lipopolysaccharide (LPS) infusion into mammary glands (IM), the response to intrateat (IT) LPS infusion has not yet been explored. This study investigated the mammary immune response following IT LPS infusion in goats and examined the distribution of LPS within the mammary gland following both IT and IM infusions. Lactating goats received either an IT infusion of 1 μg LPS from Escherichia coli O111 in 0.5 mL of saline, or saline alone as a control. Following IT LPS infusion, goats exhibited mild and localized inflammation in the mammary gland, as indicated by increased somatic cell counts and milk amyloid A, without significant changes in other major inflammatory or antimicrobial markers. In addition, distribution analysis showed that the IM infusion was widely dispersed throughout the mammary glands and teats, while IT infusion was primarily localized. These results suggest that IT LPS challenge induces a relatively mild and localized inflammatory response, and that the site of exposure may influence both the spatial characteristics and intensity of the mammary immune response.