S100A7, an inflammation-associated protein, plays a critical role in the host’s immune defense; however, its relationship with mastitis in dairy goats has not been extensively studied. In this study, based on clinical udder examinations, somatic cell count (SCC), and milk bacteriological culture (BC), a total of 84 dairy goats were classified into three groups: healthy (n = 25), subclinical mastitis (n = 36), and clinical mastitis (n = 23). The concentration of S100A7 in subclinical mastitis goats was significantly higher than in healthy individuals (p = 0.0056) but showed no significant variation from clinical mastitis goats (p = 0.8222). A weak positive correlation was found between log₁₀ SCC and milk S100A7 concentration (R = 0.05249), following the regression equation Y = 0.1446 × X + 12.54. Receiver operating characteristic (ROC) analysis of log₁₀ SCC and S100A7 concentration showed that, for subclinical mastitis goats, the area under the curve (AUC) of log₁₀ SCC was 0.9222 (p < 0.0001), while that of S100A7 was 0.7317 (p = 0.0022). In clinical mastitis goats, AUC values were 0.9678 (p < 0.0001) for log₁₀ SCC and 0.5487 (p = 0.5634) for S100A7 concentration. Immunohistochemical analysis revealed that S100A7 was weakly expressed in the alveoli of healthy mammary glands but strongly expressed in the collapsed alveoli of mastitic goats. Overall, S100A7 expression was significantly elevated in mastitic mammary glands compared to healthy ones. These findings highlight the influence of mastitis on S100A7 expression and milk concentration, demonstrating its limited correlation with SCC and suggesting a potential role of S100A7 in the mammary immune defense of dairy goats.
