Evaluation of the characteristics of ram sperm diluted with Thymus-vulgaris essential oil using phase-contrast microscope and CASA software

The ability of sperm to perform fertilization depends on various characteristics such as movement, viability, and sufficient volume. The present study was conducted to investigate the effect of Thymus vulgaris essential oil on the motility characteristics of ram sperm using phase-contrast microscope and CASA (Computer Assisted Sperm Analyzer) software. For this purpose, semen was collected twice a week from four rams. Initial evaluations included volume, wave motility, progressive motility, non-progressive motility and survival percentage of sperms. Then sperm samples were mixed with standard index Tris-based diluent, 20% egg yolk, 7% glycerol, plus 0, 100, 200 and 400 µg of Thymus vulgaris essential oil per ml. After bringing the temperature of the sperm samples to 5 degrees Celsius in the refrigerator, they were placed at 4 cm above liquid nitrogen for 10 minutes and finally immersed in it. The samples were thawed on days 0 and 30 of the experiment. Traits which were investigated during freezing and thawing days included total and progressive motility, non-progressive motility, viability percentage, MDA (Malondialdehyde) and CASA characteristics. The results showed that the percentage of viability and mobility decreased significantly during the experiment (p<0.001). The treatments of 100, 200 and 400 µg Thymus vulgaris essential oil had the most significant percentages compared to the control group in the characteristics of progressive and total motility, viability and CASA (p<0.001). Malondialdehyde had significantly decreased in the 100 and 200 treatments compared to the 400 and control treatments (p<0.001). The results of the present study showed that diluents containing Thymus vulgaris essential oil improve sperm motility and viability during freezing.