Effects of Orvus ES Paste on the Motility and Viability of Yak (Bos Grunniens) Epididymal and Ejaculated Spermatozoa After Freezing and Thawing

BACKGROUND: The addition of the detergent Orvus ES Paste (OEP) to semen freezing extenders has been observed to improve the post-thaw survival and longevity of spermatozoa from various species but has never been evaluated for yak spermatozoa. OBJECTIVE: This study evaluated the effects of OEP on the post-thaw motility and viability of epididymal and ejaculated yak spermatozoa. MATERIALS AND METHODS: Semen samples were frozen and thawed in semen freezing extender supplemented with 0%, 0.375%, 0.75% or 1.5% OEP. The motility and viability of frozen-thawed spermatozoa were evaluated before and after 3 h of incubation. RESULTS: The addition of 0.75% OEP to the freezing extender significantly improved the mean motility and viability values of both the epididymal and ejaculated spermatozoa immediately after thawing, but the beneficial effects on motility disappeared after 3 h of incubation. CONCLUSION: Our findings indicate that the addition of 0.75% OEP is effective for the preservation of yak spermatozoa.