Evaluation of ram semen enrichment with oleic acid on different spermatozoa parameters during low temperature liquid storage

The purpose of the current experiment was to evaluate the protective effect of oleic acid on ram spermatozoa parameters during storage at refrigerator temperature. Ejaculates were collected from rams, pooled, diluted with extender and enriched with 0 (control), 0.125 (O 0.125), 0.25 (O 0.25), 0.5 (O 0.5) and 1 (O1.0) mM oleic acid at a final concentration of 500 × 106 spermatozoa/mL. Spermatozoa kinematics, viability and spermatozoa membrane integrity were evaluated by using computer-assisted sperm analysis (CASA), eosin-nigrosin staining and hypo-osmotic swelling (HOS) test, respectively. In addition, amounts of malondialdehyde (MDA), total antioxidant capacity (TAC), nitric oxide (NO) and superoxide dismutase (SOD) activities were assessed in the medium and spermatozoa at 0, 24, 48 and 72 h of storage. Enrichment of semen with oleic acid resulted in a significant (P < 0.05) increase in total motility, forward progressive motility and VCL (curvilinear velocity, μm/s) of O 0.5 and O1.0 groups at 48 and 72 h of storage. In addition, viability and spermatozoa membrane functionality were greater in O 0.5 (81.81 ± 2.29% and 72.10 ± 2.63%) and O1.0 (82.32 ± 2.36% and 74.53 ± 1.90%) groups compared to the control group (73.28 ± 1.60% and 59.34 ± 2.12%) at 72 h (P < 0.05). The measurement of MDA levels in spermatozoa showed that, there were higher in control group (0.84 ± 0.02 and 0.86 ± 0.04 μmol/g protein) in comparison with the O 0.125 (0.67 ± 0.05 and 0.69 ± 0.03 μmol/g protein), O 0.25 (0.62 ± 0.03 and 0.66 ± 0.02 μmol/g protein), O 0.5 (0.62 ± 0.02 and 0.65 ± 0.06 μmol/g protein) and O1.0 (0.60 ± 0.01 and 0.61 ± 0.01 μmol/g protein) groups at 48 and 72 h of storage (P = 0.002). Moreover, higher amounts of TAC were obtained in oleic acid treated groups compared to control group in spermatozoa and medium at 48 and 72 h (P < 0.05). Nitrosative status was lower and SOD activities were higher in spermatozoa of oleic acid treated groups than the control group at 48 and 72 h (P < 0.05). Our results indicated that oleic acid with the dose of 0.5 and 1 mM would enhances ram semen quality during liquid storage at 48 and 72 h.