Effects of antioxidants on motility and membrane integrity of chilled- stored stallion semen

The use of chilled-stored stallion semen is limited by its relatively short-term fertilizing capacity. An important reason for the decrease in fertility during storage is the peroxidation of sperm membrane lipids. In this study, effects of the antioxidants ascorbic acid (0.45 and 0.9 g/L) and catalase (0.45 x 106 and 1.8 x 106 units/L) on chilled-stored stallion semen were investigated. Semen was collected by artificial vagina from 7 stallions and was diluted with skim milk extender or glycin extender. Sperm motility and membrane integrity were investigated after dilution and after 24, 48 and 72 h at 5°C. Ascorbic acid significantly increased the percentage of membraneintact spermatozoa at 24, 48 and 72 h at 5°C when compared with that of the controls (P<0.05), irrespective of the extender. Ascorbic acid decreased the percentage of progressively motile spermatozoa (P<0.05) at a concentration of 0.9 g/L in glycin extender. Catalase decreased (P<0.05) progressively motile spermatozoa after 24, 48 and 72 b at 5°C in skim milk extender at a concentration of 1.8 x 106 units/L. Catalase decreased (P<0.05) the percentage of membraneintact spermatozoa at 24 h. Motility and membrane integrity of spermatozoa after dilution with glycin extender containing catalase did not differ from the controls. In conclusion, ascorbic acid has protective effects on sperm membrane integrity in diluted stallion semen.