Effects of years of storage (1, 5, and 7 years) on bovine sperm ultrastructure, oxidative status, and fertilizing capacity.

The cryopreservation technique for sperm is a widely recognized approach utilized in artificial insemination. Previous studies have demonstrated that sperm quality is influenced by ice crystal formation and oxidative stress during the freezing process. Moreover, the time of cryostorage also has an impact on sperm quality. Nevertheless, there is a scarcity of comprehensive research concerning the years of storage on bovine sperm. In this study, bovine sperm samples cryopreserved for 1, 5, and 7 years were analyzed for motility, functionality membrane integrity, oxidative stress markers, apoptosis, DNA fragmentation, and fertilizing ability. Post-thaw assessments revealed a significant decline in antioxidant capacity and an increase in lipid peroxidation and apoptosis in the 7-year group compared to the 1-year group (P < 0.05). Despite relatively stable sperm membrane and acrosome integrity, DNA damage and oxidative stress were elevated over time. Notably, while cleavage rates remained unchanged, blastocyst development was significantly reduced after 7 years of storage (P < 0.05). These findings suggest that prolonged cryopreservation negatively affects sperm function and embryo development, emphasizing the need to consider storage duration in reproductive applications.