Improvement in frozen-thawed ram sperm quality parameters by adding Mentha piperita L. extract in extender

The aim of current study was to evaluate the effect of Mentha piperita extract as a natural antioxidant on quality of frozen-thawed ram sperm. In this study, four Moghani ram were used for semen collection twice a week. Then semen samples were pooled and diluted with extenders supplemented with different concentrations of Mentha piperita extracts (0, 2, 4, 8, 12 and 16 mL per dL diluent solutions). Following cooling and freezing, semen samples were stored in liquid nitrogen until evaluation. After thawing, the sperm dynamic parameters were evaluated using CASA system. The results showed that the addition of 4 and 8ml/dl extracts resulted in higher (p < 0.05) percentages of total motility compared to control. Addition of 4 ml/dl extract improved progressive motility compared to control group and higher levels of extract groups (P <0.05). The percentages of LIN, STR and VSL were higher (P<0.05) in the extender containing 8 mL/dL extract. Addition of 4 and 8 mL/dL extract to the extender significantly (P<0.05) improved VCL and VAP parameters. Addition of 4 and 8ml/dl extract improved the percentage of viability and sperm plasma membrane integrity compared to control (P <0.05). Sperm morphology was not affected by treatments. In conclusion, supplementation of extender with Mentha piperita L. extract improves post-thawed ram sperm quality in a dose dependent manner.