Role of Oleic Acid and Trehalose on Frozen-Thawed Ram Semen

Abstract

BACKGROUND: When sperm are cryopreserved, reactive oxygen species (ROS) are formed that are detrimental to the sperm. OBJECTIVE: To evaluate the effects of oleic acid and trehalose added to ram semen extender on sperm parameters, lipid peroxidation (MDA), and superoxide dismutase (SOD) enzyme levels of spermatozoa following the freeze/thawing processes. MATERIALS AND METHODS: Ejaculates were collected from four rams and pooled at 35°C. Pooled ejaculates were diluted with oleic acid at 0 mM and trehalose at 0 mM (O0 T0) as the control. The Tris-based extender was supplemented with either 0.5 (O0.5) or 1 (O1) mM of oleic acid or 25 (T25) or 50 (T50) mM of trehalose alone, and in combination [0.5 mM oleic acid + 25 mM trehalose (O0.5T25), 0.5 mM oleic acid + 50 mM trehalose (O0.5T50), 1 mM oleic acid + 25 mM trehalose (O1T25) and 1 mM oleic acid + 50 mM trehalose (O1T50)]. The semen was frozen by the traditional liquid nitrogen vapour method and stored at –196°C in the liquid nitrogen tank. RESULTS:Semen extender containing O1T25 significantly improved the total motility, when compared with other treatment groups (P < 0.05), except for O1T50. O1T50 had a higher viability rate than any other treatment. The addition of O1T25 and O1T50 increased DNA and membrane integrity of spermatozoa post-thawing compared to other treatments (P<0.05). The level of MDA was significantly (P<0.05) lower in extenders supplemented with O1, O0.5T25, O0.5T50, O1T25 and O1T50 compared to the other treatment groups. In addition, SOD levels were higher in groups treated with O1T25 and O1T50 than the other treatment groups (P<0.05). CONCLUSION: The addition of a combination of oleic acid and trehalose concentrations to Tris-based extender improved the quality of ram semen post-thawing.