In Vitro and In Vivo Efficiency of Extenders Added to Thawed Stallion Semen.

BACKGROUND: Addition of extenders to thawed semen could improve fertility. OBJECTIVE: To determine the efficiency of extenders to increase viability of thawed semen, measured by sperm parameters in vitro and pregnancy rates after artificial insemination (AI). MATERIALS AND METHODS: Sperm motility and acrosin activity were measured during a thermoresistance test (TRT). RESULTS: Progressive motility decreased (P<0.05) after 30 min in thawing semen treated with saline solution (SS) and only after 60 min with Tyrode's solution (TS) or freezing diluent (FD). The total motility decreased (P<0.05) after 60 min in thawed semen treated with SS, and after 90 min in thawed semen containing TS or FD. The acrosin activity decreased (P<0.05) after 60 min during the TRT, but there was no difference among treatments throughout the TRT. The pregnancy rates were similar among thawed-semen supplemented with SS, TS or FD. CONCLUSION: The extenders neither improve sperm parameters nor enhance AI results.