Optimization of protocol for stallion semen cryopreservation

The aim of the preliminary study was to improve success of cryopreservation of stallion spermatozoa. The effect of different equilibration lengths and two techniques for freezing of stallion semen was evaluated, based on motility and viability parameters. Fresh semen was diluted with BotuCrio extender and divided into 3 groups equilibrated for 0.5h, 2h, and 4h. Subsequently, half straws of each group were cryopreserved in the vapours of the liquid nitrogen or in the automatic freezer. Results of stallion spermatozoa motility and progressive motility showed decreasing trend with increased time of equilibration. Moreover, a significant difference (p < 0.05) for the percentage of spermatozoa producing ROS was found between semen frozen in the vapours of the liquid nitrogen compared to semen cryopreserved by the automatic freezer in the same equilibration time. Nevertheless, results of this study are of preliminary character. Experiments using higher number of individuals need to be tested in order to find the best procedure for semen cryopreservation of Slovak national horse breeds.