Catalase Effect on Sperm Storage and Fertilization Capacity of Capercaillie ( <i>Tetrao urogallus</i> )

The capercaillie (Tetrao urogallus), a critically endangered species, faces significant challenges due to habitat loss and population decline. Assisted reproductive technologies, including semen preservation and artificial insemination (AI), are vital for conservation efforts. Although the results are controversial, it has been reported that antioxidants, such as catalase, play an important role in protecting against oxidative damage caused by reactive oxygen species during short- and long-term sperm storage. This study evaluated the protective effects of catalase (200 IU/mL) on stored/frozen-thawed capercaillie sperm. The possible protective or harmful effect of catalase on fertilizing ability was assessed after AI with fresh and stored semen. Results indicated that catalase had no significant effect on sperm motility, viability, or DNA integrity after liquid storage or freezing/thawing. Fertility rates decreased sharply after semen storage for 6 h at 5°C even in the presence of catalase. Catalase-treated samples maintained similar fertility rates to controls. The study also provided the first evidence of sperm storage duration within female capercaillies, which lasted up to 21 days. These findings underscore the challenges of semen preservation in wild species and highlight the need for further exploration of alternative antioxidants to optimize storage media.