Effects of Long-term Storage on Some Spermatological Parameters in Cryopreserved Bull Semen.

BACKGROUND: The effect of the long-term storage in liquid nitrogen on semen quality has not be reported. OBJECTIVE: The study measured the spermatological parameters of bull sperm after the long-term and short-term storage. MATERIALS AND METHODS: Vintage semen (obtained from 5 Brown Swiss bulls and frozen 30 years ago) and newly frozen semen collected from 5 bulls of the same breed and prepared at the International Center for Livestock Research and Training were used. For each bull, 10 straws (0.25 ml) were thawed and pooled. Sperm samples were analyzed by flow cytometry, computer assisted sperm analysis, and total oxidant-antioxidant levels were also tested. RESULTS: The ratios of necrotic (P < 0.001) and apoptotic (P = 0.006) spermatozoa, and the ratios of total antioxidant status (TAS) and total oxidant status (TOS) were significantly higher (P < 0.001) in long-term frozen spermatozoa. However, the early necrotic ratios (P < 0.001), velocity average pathway (VAP) (P = 0.008) and velocity curvi linear (VCL) (P = 0.01) values of long-term frozen semen were lower compared with short-term frozen semen. While necrotic and apoptotic spermatozoa ratios and total oxidant level were higher, VAP/VCL ratios were lower in long-term frozen sperms compared to short-term frozen semen. CONCLUSION: Long-term storage of sperm may adversely affect the spermatological and oxidative parameters of Brown Swiss bull spermatozoa.