Comparison of two different extenders for cryopreservation of epididymal dog sperm.

The collection of epididymal sperm is an option for preservation of germplasm of genetically superior animals that need to be orchiectomized or have died. The extender type used to freeze sperm is important to avoid spermatozoal membrane damage and to preserve semen quality after cryopreservation. The objective of this study was to verify the effects of a commercial bovine extender (Bovimix(®); Nutricell, Campinas) and a traditional TRIS-citric acid-glucose-egg yolk-7% glycerol extender on cryopreservation of canine epididymal sperm. The testes of 13 adult dogs were kept at 5 °C for 24 h in saline solution, and epididymal sperm was recovered in Ringers solution without lactate and were evaluated for motility. Samples with ≥ 80% motility were pooled and then divided before dilution and packaging in 0.5 ml plastic straws, equilibration at 4 °C for 1 h, freezing in nitrogen vapour for 20 min and storing at -196 °C. The straws were thawed at 56 °C for 10 s and were evaluated for motility by computer assisted analysis (CASA). The semen parameters, sperm movement index, linearity, total motility and rapid progressive motility were statistically higher in Bovimix(®) than TRIS. In contrast, amplitude of lateral head displacement, slow sperm and static sperm were lower in Bovimix(®). Despite the high percentage of sperm defects in epididymal cells, regardless of the extender, we concluded that Bovimix(®) is a viable alternative for the freezing of canine epididymal sperm.