Effect of different extenders on in vitro characteristics of feline epididymal sperm during cryopreservation.

To evaluate and compare the efficacy of various extenders for the cryopreservation of epididymal cat spermatozoa, two experiments were planned. Bovine and equine commercial extenders in the experiment 1 and TRIS-egg yolk-based extenders in experiment 2 were separately studied since the number of sperm collected per cat is reduced. Epididymal sperm samples were packaged into 0.25-ml straws and frozen. Vigour, motility, morphology, acrosome status, sperm viability and functional membrane integrity were assessed at collection, after cooling and after thawing, while DNA integrity was evaluated at 0- and 6-h post-thaw. Experiment 1 compared the effect of three non-feline commercial extenders - based on TRIS-egg yolk (Triladyl), egg-yolk-free medium (AndroMed) and skimmed milk-egg yolk (Gent) - on the quality of frozen-thawed epididymal cat sperm. Values for sperm motility and functional membrane integrity in cooled sperm diluted in Triladyl were higher (p < 0.001) than those recorded for Andromed and Gent. Except sperm morphology, the other assessed characteristics showed significant higher values in frozen-thawed sperm diluted in Triladyl than in Andromed and Gent extenders. Experiment 2 analysed the effects of three TRIS-egg yolk-based extenders, one non-feline commercial (Triladyl) and the other two prepared using different monosaccharides (glucose and fructose), on freezing-thawed sperm. Results showed that specifically prepared extenders for cryopreservation of feline spermatozoa performed better than the commercial extender Triladyl, although sperm quality during the freezing-thawing process did not significantly differ associated with the type of monosaccharide (glucose vs fructose) added to the mentioned extenders. Although TRIS-egg yolk-based extenders prepared in experiment 2 improved sperm cryoprotection, Triladyl remains a good option for practitioners who, for ease of use and availability, prefer to work with commercial extenders.