Influence of lycopene and cysteamine on sperm and oxidative stress parameters during liquid storage of ram semen at 5 °C

Ejaculates were collected from six Merino rams with the aid of an artificial vagina twice a week. The ejaculates containing spermatozoa with >80% forward progressive motility and concentrations higher than 2 × 109 spermatozoa/ml were pooled. The present study included two experiments. In experiment 1, each pooled ejaculate was divided into four equal aliquots and diluted (37 °C) with the Tris based extender, containing 0 (control), 0.5, 1 and 2 mM lycopene, at a final concentration of approximately 400 × 106 sperms/ml (single step dilution), In experiment 2, cysteamine at concentrations of 0 (control), 0.5, 1 and 2 mM, was used as an additive in the extender, and the procedure explained above was applied for the division of aliquots and the dilution of semen. Diluted semen samples were kept in glass tubes and cooled from 37° to 5 °C in a cold cabinet, and maintained at 5 °C. Sperm and oxidative stress parameters were evaluated after 0, 24, 48 and 72 h of storage at 5 °C. The extender supplemented with 0.5 mM lycopene resulted in higher mitochondrial activity rate (p < 0.05) in comparison to the control group at 72 h of storage. Lycopene at 0.5 mM dose led to higher sperm motility rate (p < 0.05) when compared to 2 mM lycopene group at 72 h of liquid storage. As regards oxidative stress parameters, only 2 mM lycopene increased total glutathione levels (p < 0.05) at 0 h of storage. The extender supplemented with 1 mM cysteamine gave higher motility (p < 0.05) at 48 h compared to control. As regards oxidative stress parameters, 1 and 2 mM cysteamine at 48 h and 1 mM cysteamine at 72 h increased total glutathione levels (p < 0.05) compared to control groups. Cysteamine at 1 and 2 mM doses decreased lipid peroxidation (p < 0.05) at 0 h of liquid storage compared to control. Our data suggest that lycopene at 0.5 and 2 mM and cysteamine at 1 and 2 mM doses can be added to Tris based extender for improving the ram sperm motility, viability, mitochondrial activity and oxidative stress parameters during the liquid storage.