Role of antioxidant additives in the protection of the cryopreserved semen against free radicals

The aim of this study was to assess the effects of the addition of antioxidants (vitamin E and cysteine) to freezing media on standard qualitative parameters (motility, viability, HOST) and oxidative parameters (lipid peroxidation) of frozen-thawed ram semen. Ejaculate samples were collected with artificial vagina from 2 adult Merino Palas rams, during normal reproduction season (October- December 2009) and diluted with a Tris-base extender containing vitamin E (1mM), cysteine (10mM) and without antioxidants (control). Diluted semen was cooled to 4 o C and frozen in 0.25 ml straws, prior to being stored in liquid nitrogen. Semen parameters were investigated after thawing. The lipid peroxidation level was examined by measuring the production of malondialdehyde using the thiobarbituric acid method. The results show that both vitamin E and cysteine increased the percentage of sperm motility and viability (p<0.05), but reduced the lipid peroxidation (LPO) level. A significant negative correlation was observed between the percentage of motile spermatozoa and the LPO level (p<0.05).