Comparison of different carrier-compounds and varying concentrations of oleic acid on freezing tolerance of ram spermatozoa in tris-citric acid-egg yolk plasma semen diluent.

The current study was conducted to determine the optimal concentration carrier-compound for oleic acid (OA) among dimethyl sulfoxide (DMSO), liposome and β-cyclodextrin on ram spermatozoa cryosurvival. The preliminary experiment was designed to ascertain the optimal concentration of egg yolk plasma. In Experiment 1, semen was placed in a diluent containing different concentrations of OA dissolved in DMSO (0.125, 0.25, 0.50, 1, 2, 4 and 8 mM). In Experiments 2 and 3, effects of liposome loaded-OA and β-cyclodextrin-OA complexes (0.25, 0.50, 1 and 2 mM) on semen cryopreservation were evaluated. In Experiment 4, optimal concentrations of OA were determined, based on results from previous experiments. Spermatozoa viability, kinematics, plasma membrane integrity, malondialdehyde, superoxide dismutase activity and total antioxidant status of samples were evaluated. Results indicated varying concentrations of OA had different effects on sperm kinematics, viability and membrane functionality after freezing/thawing (P < 0.05). In addition, inclusion of OA in liposomes or combinations with β-cyclodextrin resulted in greater values for spermatozoa motion variables compared with DMSO dissolved-OA (P < 0.05). Inclusions of OA at 0.25 and 0.50 mM led to a reduction in amounts of lipid peroxidation when there was inclusion of liposome and β-cyclodextrin as carrier-compounds (P < 0.05). Activity of SOD was similar with inclusion of different concentrations of OA or carrier-compounds, but total antioxidant capacity was affected by OA concentration and carrier-compound type (P < 0.05). The results highlight the importance of carrier-compound type and concentrations of OA on ram spermatozoa during cryopreservation.