Effect of Different Permeable Cryoprotectants on the Quality of Cat Epididymal Spermatozoa

BACKGROUND: Permeable cryoprotectants (CPAs) are required for successful sperm cryopreservation. OBJECTIVE: To investigate the efficacy of adding different CPAs to a freezing extender on cat epididymal sperm quality. METHODS: Epididymal spermatozoa were suspended in Tris-glucose-citrate-egg yolk extender supplemented either with glycerol, methanol, formamide, ethylene glycol (EG), propylene glycol (PG) and dimethylsulfoxide (DMSO), all at 5% (v/v), and then cryopreserved. Sperm motility, viability, functional membrane integrity, morphology and acrosome integrity were examined at post-thaw. RESULTS: Glycerol, formamide, EG and DMSO exhibited good, comparable cryoprotective effects, whereas PG showed moderate cryoprotection. Sperm viability in PG was lower than that in glycerol and EG, but was not different in formamide and DMSO. Contrarily, the least efficacy was observed in methanol. Interestingly, the CPA type has no effect on functional membrane integrity and morphology. CONCLUSION: Using Tris-glucose-citrate-egg yolk extender, formamide, EG and DMSO could substitute glycerol as permeable CPAs for cat epididymal sperm cryopreservation.