The Role of Thiol–Disulphide Balance and Specific Antioxidant Enzymes in Oocyte Quantity and Quality in Cattle

Oxidative stress and redox homeostasis play crucial roles in ovarian function, influencing oocyte quality and developmental competence. This study evaluated the population-level associations between thiol-disulphide homeostasis, oxidative stress biomarkers, antioxidant enzyme activity, and oocyte quantity and quality in cattle. Blood and follicular fluid samples were analysed from cattle to assess total thiol (TTL), native thiol (NTL), disulphide (DS), nitric oxide (NO), superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) levels. Oocytes were collected and classified based on morphological characteristics. Statistical analyses revealed a positive correlation between TTL and total oocyte count (TOC), suggesting that higher thiol availability enhances oocyte production. Conversely, elevated NTL levels were negatively associated with oocyte quality, indicating that an imbalance in thiol-disulphide homeostasis may impair follicular development. GPX activity exhibited a significant negative association with both TOC and high-quality oocyte count (HQOC), suggesting that excessive antioxidant activity might disrupt essential redox signalling pathways required for oocyte maturation. However, SOD, CAT and NO levels were not significantly correlated with oocyte count or quality, indicating a complex interplay between oxidative stress markers and reproductive efficiency. These findings demonstrate significant associations between thiol-disulphide balance, GPX activity, and both total and HQOCs, highlighting the relevance of redox status in follicular physiology. Further research is needed to explore targeted antioxidant interventions to optimise reproductive outcomes in livestock. Understanding the role of oxidative balance in oocyte maturation may contribute to improving assisted reproductive technologies (ART) such as in vitro fertilisation (IVF) and embryo transfer in cattle.