Comparison of Mitochondrial Function in Boar and Bull Spermatozoa Throughout Cryopreservation Based on JC-1 Staining.

BACKGROUND: Poor reproductivity hampers the commercialization of cryopreserved boar semen. OBJECTIVE: This study was to determine the differences in the sperm mitochondrial function between boar and bull semen at different cryopreservation stages. MATERIALS AND METHODS: Boar and bull fresh, equilibrated, and frozen-thawed spermatozoa were evaluated for mitochondrial function using JC-1 under a fluorescent microscope. RESULTS: Bull and boar percentage of spermatozoa staining green (PSSG) showed no difference between fresh and equilibrated semen (P> 0.05). However, frozen-thawed bull and boar semen demonstrated significantly higher PSSG (P < 0.01) than fresh and equilibrated semen. Frozen-thawed boar semen represented a significantly higher PSSG (P < 0.01) than bull semen. CONCLUSION: Negative cryopreservation influence on boar and bull spermatozoa was not significantly produced by pre-freezing procedures, but rather by freezing and thawing. Cryopreservation has more pronounced negative effects on boar than on bull spermatozoa, which partly explains lagged commercialization of frozen boar semen.