Supplementation of the cooling medium with antioxidants has been suggested as an effective way to improve sperm quality during the chilling process. This study was designed to investigate the effect of supplementing sperm cooling medium with zinc oxide nanoparticles (NZnO) on ram semen quality. Semen samples were diluted in extenders supplemented with five different concentrations of NZnO (0, 50 µM/mL, 100 µM/mL and 200 µM/mL) or 100 µM/mL zinc oxide (ZnO) then frozen using a standard protocol. Various in vitro sperm qualities were assessed after thawing. No significant differences in average path velocity, straight-line velocity, curvilinear velocity, acrosome integrity and acrosome integrity were found among the treatments. Extender supplementation with 100 µM/ml NZnO presented higher (P<0.05) total motility, progressive motility, membrane integrity, mitochondria membrane potential, viability and lower malondialdehyde concentration compared to other groups. A dose of 200 µg/mL of NZnO had a toxic effect on these parameters (P≤0.05). In conclusion, NZnO as an antioxidant can enhance the quality of sperm in ram after of post- thawed process.
