Cryopreservation of Stallion Spermatozoa with INRA96 and Glycerol

The aim of the present study was to improve success of cryopreservation of stallion spermatozoa. Semen from eleven stallions was collected and frozen in INRA 96 with two different concentrations of glycerol (3.5% and 6.0%) and compared with a control freezing process. The mean post-thaw motility for the eleven stallions of 57.93% (3.5% glycerol) and 66.50% (6.0% glycerol), which was statistically higher (P < 0.05) when compared with the mean post-thaw motility (39.7%) for semen in a control egg-yolk extender (Equipro® CryoGuard™ Complete, Minitube). The Equipro® CryoGuard™ Complete is a commercial semen freezing protocol that has been one of the standard processes used in our laboratory for freezing equine spermatozoa. INRA 96 with 6% added glycerol was used in the fertility trial as it provided the highest spermatozoa survival. To evaluate fertility of the frozen semen, eight mares were bred over two cycles with both fresh and frozen semen. The pregnancy rate of mares bred with frozen semen (55.6%) was not statistically different (P > 0.05) from the pregnancy rate of mares bred with fresh semen (55.6%). INRA 96 with 6.0% glycerol improved the survivability of stallion spermatozoa through the cryopreservation process, and subsequent fertility was not different (P > 0.05) from fresh, extended semen.