Effects of the addition of docosahexaenoic acid and alpha-tocopherol on quality of equine spermatozoa stored at 5 degrees C

Plasma membrane composition has impact on phase transition from liquid crystal to gel state of cooled sperm cell. The incorporation of polyunsaturated fatty acids increases its fluidity and can contribute to sperm motility. The aim of this study was to compare the effect of adding docosahexaenoic acid (DHA) and alpha-tocopherol (alpha-Toh) to the cooling extender, singly or combined, to the equine sperm parameters, submitted to cooling, up to 72 hours. Two ejaculates of ten stallions collected with artificial vagina were used, and evaluated for motility, plasma membrane integrity, chromatin fragmentation, mitochondrial activity and lipid peroxidation, according to the following treatments: C; DHA; alpha-Toh; DHA/alpha-Toh; EtOH 100: and EtOH 140 (corresponding to control; 10 ng mL(-1) of DHA; 2 mM of alpha-Toh; : 10 ng mL(-1) of DHA + 2 mM of alpha-Toh; 100 mu L of ethanol and 140 mu L of ethanol respectively). DHA treatment showed higher motility (68.2 +/- 12.3; p < 0.05) when compared to control (62.1 +/- 16.2), DHA/alpha-Toh (61.3 +/- 12.7) and EtOH (58.1 +/- 8.6) groups. In lipid peroxidation assay, the control group showed 2,506.2 +/- 796.4 ng of MDA 10(8) spermatozoa(-1), being significantly higher (p < 0.05) than the groups treated with DHA (2,036.0 +/- 687.0), alpha-Toh (1,890.8 +/- 749.5) and DHA/alpha-Toh (1,821.1 +/- 627.2). In conclusion, alpha-Toh was effective in diminishing lipid peroxidation of equine sperm subjected to cooling, and DHA improved sperm motility and, in spite of being a polyunsaturated fatty acid with high susceptibility to peroxidation, reduced lipid peroxidation.