ABSTRACT
The aim of the present study was to investigate the effect of supplementing rabbit semen extender with zeolite loaded with different charges (Z+ or Z-, Z±) on sperm cryopreservation. Semen was collected from six healthy, fertile New Zealand rabbit bucks using an artificial vagina. The collected ejaculates were pooled and diluted with a tris-yolk fructose (TYF) extender supplemented with Z± (+16, +12, +8, -16, -12, and -8) at a concentration of 1% for a final sperm concentration of 25 × 106 sperm cells/mL. The diluted semen samples were then cryopreserved in 0.25 mL straws and stored in liquid nitrogen for 1 month. To evaluate sperm quality, we examined sperm progressive motility, vitality, morphological abnormalities, and plasma membrane integrity. In addition, apoptotic rates were determined using flow cytometry and by examining sperm ultrastructure under a transmission electron microscope (TEM). Moreover, total antioxidant capacity and markers of lipid peroxidation were measured in the extender after thawing. Addition of Z± had a positive effect on progressive motility, vitality, and membrane integrity after an equilibration period and post-thawing as compared with the controls (P < 0.05). Z± supplementation, particularly with a strong negative charge, also decreased the percentages of apoptotic and necrotic sperm cells compared to controls (P < 0.05), as shown both by flow cytometry and TEM. This was not associated with any marked effects on the oxidative biomarkers in the extender. In conclusion, addition of Z± to semen extender improved post-thawing sperm quality by improving sperm characteristics, decreasing apoptosis, and minimizing sperm damage during cryopreservation.
