Factors affecting storage of Slovak native rabbit semen in the gene bank

In this study, fresh and frozen-thawed semen of Nitra and Zobor rabbit breeds were evaluated for potential inter-breed or inter-male differences in sperm quality traits. Individual male semen from four rabbits of each breed were diluted (v:v; 1:1) in a freezing medium composed of a commercial diluent, 16% of dimethyl sulphoxide (DMSO), 4% of Ficoll 70 and 2% of sucrose and frozen in liquid nitrogen vapours before being plunged into liquid nitrogen. Different motility traits, viability and plasma membrane integrity of fresh and frozen-thawed semen were evaluated in vitro using computer-assisted sperm analysis and flow cytometry. To evaluate the sperm fertilization ability, artificial insemination of fresh and frozen-thawed sperm was performed. Our results showed the effect of breed (P ≤ 0.05) on frozen-thawed sperm viability and plasma membrane integrity. Moreover, individual variability in semen quality among the rabbits was revealed (0.31 to 0.71 among quality traits). Our results thereby confirmed that the cryopreservation procedure could not ensure comparable sperm post-thaw survival for different breeds or males. Nevertheless, correlations between numbers of fresh total motile and progressively moving sperm and several quality parameters measured post thawing were revealed. Therefore, we suggest that the objective assessment of fresh rabbit sperm motility may be an effective indicator of frozen-thawed semen quality. Consequently, regular semen assessment is required in order to preserve good-quality insemination doses from native breeds.