Effect of density gradient on sperm parameters of stallion frozen semen

Abstract

performed on donkeys. The aim of this study was to determine if such centrifugation of donkey semen after 24 hours of cooled storage improves sperm motility. Semen was collected from four Andalusian donkeys by artificial vagina. Two aliquots of each semen sample were extended with INRA96, cooled slowly to 5 oC and then stored in a styrofoam box. Single layer centrifugationwas carried out after 24 hours of cooled storage using the silane-coated silica colloid Androcoll-E Large. Computer assisted sperm analysis (CASA) was performed and sperm motility, total motility and progressive motility (considered on settings when straightened percentage was equal or higher than 75%), were statistically compared between semen aliquots processed or not by colloid centrifugation. Results were expressed as mean standard error. The yield of selected spermatozoa (number of spermatozoa in sperm pellet/ number of spermatozoa in initial load) was 12.94 1.10%. Significant differences (P < 0.05) were found between colloid-selected and unselected sperm samples for progressive sperm motility (52.6 7.1% vs 30.2 5.8%). However, no significant differences were found for total sperm motility (77.7 6.4% vs 64.6 8.1%). These results suggest an additional option for improving sperm motility in donkey semen. However, these are preliminary results and further studies should be performed increasing the number of animals and the semen parameters assessed. In conclusion, centrifugation through a single layer of colloid after 24 h of cooled storage increased progressive sperm motility in a limited number of donkey semen samples. PMI (%) 59 68 40 47