Seasonal changes in thiol–disulfide homeostasis, oxidant–antioxidant status, and lipid profile in healthy dairy cows

Thiol/disulfide homeostasis is a key component of the antioxidant defense system and studies on the determination and improvement of thiol/disulfide homeostasis may contribute to the prevention of the adverse effects of oxidative stress on animal production, and welfare. The purpose of this study is to investigate the total thiol, native thiol and disulfide levels, together with total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), paraoxonase-1 (PON1) activity and lipid profile in Simental and Montofon dairy cows across different seasons. Blood samples were collected from animals in May and November. Serum concentrations of total thiol, native thiol, disulfide, TAS, TOS and PON1 were measured using colorimetric methods. Concentrations of triglycerides (TG), total cholesterol (TC), HDL, and LDL were measured using an automated analyzer. In both breeds, serum total thiol and disulfide levels increased in November compared with May, whereas native thiol levels decreased in November. In both the Simental and Montofon breeds, serum TOS and OSI levels increased in November compared to May, while TAS levels decreased. Also, serum HDL, LDL and cholesterol levels increased in both breeds, while PON1 levels increased only in Simental in November compared to May. According to our results, both breeds were affected by seasonal changes, but Simental cows were more sensitive than Montofon cows. Research on thiol/disulfide homeostasis in veterinary medicine is limited and this study is the first to evaluate thiol/disulfide homeostasis along with oxidative stress and lipid profiles in dairy cows across different seasons.