Influence of vitamin E on microscopic and oxidative parameters of frozen-thawed ram semen.

Cryopreservation is associated with the production of reactive oxygen substances (ROS), which lead to lipid peroxidation of sperm membranes, resulting in a loss of sperm motility, viability and fertility. The aim of this study was to assess the effects of vitamin E adding to the dilution 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, on normal season of reproduction (October-December 2009) and diluted with a Tris-base extender containing vitamin E (1 and 2mM) and without antioxidants (control). Diluted semen was cooled to 4C and frozen in 0.25 ml straw, prior to being stored in liquid nitrogen. Semen parameters including motility, the plasmatic membrane structural integrity (viability by eosin-nigrosin stain), functional membrane integrity (hipoosmotic test) and lipid peroxidation (LPO) were investigated after thawing. Lipid peroxidation level was examined by measuring the production of malondialdehyde using the thiobarbituric acid method. The results show that vitamin E has positive protection effects on the semen characteristics consequently to the freezing-thawing process.Both doses of vitamin E increased the percentage of sperm motility and viability(p<0.05), but reduced the lipid peroxidation (LPO) level. Most effective occur at the 2mM dose, though differences among the doses were non-significant (p≥0.05).