Objective: This study aimed to evaluate alterations in oxidative stress markers and thiol–disulfide homeostasis in cows with clinical and subclinical mastitis. Materials and Methods: A total of 40 cows were included and divided into five groups: clinical mastitis (n = 8), subclinical mastitis (+1, +2, +3; n = 8 for each group), and a healthy control group (n = 8). Blood samples were analyzed for glutathione (GSH), malondialdehyde (MDA), total thiol (TT), native thiol (NT), disulfide levels, and the ratios of disulfide/TT, disulfide/NT, and NT/TT. Results: Compared with the control group, cows with clinical and subclinical mastitis showed significantly lower GSH, TT, and NT levels (P 0.001), whereas MDA, disulfide concentrations, and disulfide-based ratios were markedly increased, particularly in the clinical mastitis group (P 0.001). Progressive alterations in oxidative stress markers were observed with increasing severity of subclinical mastitis (P 0.05). Correlation analyses revealed strong and significant associations between thiol–disulfide homeostasis parameters and oxidative stress markers (P 0.001). Conclusion: In conclusion, thiol–disulfide homeostasis may serve as a complementary oxidative stress–based biomarker system for the evaluation of both clinical and subclinical mastitis.
Demir et al. (2026) studied this question.