FREEZING OF EQUINE SEMEN IS INFLUENCED BY EXPOSURE TIME AND CONCENTRATION OF THE CRYOPROTECTANT GLYCEROL

BACKGROUND: Glycerol is a cryoprotectant widely used in the freezing of mammalian species' semen, but no study has demonstrated its optimum concentration and the appropriate exposure time for equine species. OBJECTIVE: To demonstrate that the exposure time (15, 30, 45, 60, 75 and 90 min) versus concentration (2, 3, 4 and 5%) of the cryoprotectant glycerol influences the freezing success of equine semen. MATERIALS AND METHODS: The ejaculate of 12 stallions were frozen in different glycerol concentrations following different exposure times. The thawed sperm was evaluated for kinetic parameters using a Computer Assisted Semen Analysis (CASA) system and cell feature parameters were assessed by flow cytometry. RESULTS: Considering the total and progressive motility of the spermatozoa, we concluded that protocols using 5% glycerol for 15 and 30 min exposure, 4% glycerol for 45 min exposure and 3% glycerol for 90 min exposure generated the best results. CONCLUSION: We suggest the use of any of these protocols for a better cryopreservation of equine semen.