Changes in Antimicrobial Component Concentrations in Goat Milk Following Intramammary Lipopolysaccharide Administration.

Mastitis is a major cause of economic losses in dairy production; however, its prevention and treatment remain challenging. Under field conditions, antimicrobial drugs are frequently administered when somatic cell counts (SCCs) are elevated and signs of inflammation are observed, even in the absence of detectable pathogens in milk. As antimicrobial therapy may be unnecessary during the healing phase of inflammation, improved indicators of the mastitis stage are required. Therefore, this study aimed to determine whether changes in milk antimicrobial component (AMC) concentrations could serve as indicators of the inflammatory stage, thereby supporting judicious antimicrobial use. Lactating Tokara goats received an intramammary infusion of lipopolysaccharide (LPS) to induce experimental mastitis, with saline-infused quarters serving as controls. Milk samples were collected for up to 120 h post-infusion to measure SCC and the concentrations of lactoferrin (LF), goat β-defensin 1 (GBD1), cathelicidin-7, S100A8, and milk amyloid A (MAA). SCC peaked at 10 h, whereas GBD1 tended to peak at 4 h, indicating early inflammation. In contrast, LF, S100A8, and MAA, together with the increasing tendency of Cath-7 levels, peaked later (36-84 h) as SCC declined, suggesting an association with the recovery phase. These findings demonstrate that temporal patterns of milk AMCs can be used to stage mastitis progression.