The cryoprotective potential of propolis supplemented in frozen-thawed bull semen; biochemical and physiological findings

In this study, the cryoprotective effect of different doses of propolis (P) on bull semen, which has solid pharmacological properties thanks to its rich phenolic components, was investigated biochemically and physiologically. Semen samples were collected from Simmental breed bulls via the artificial vagina and pooled. After dividing into five groups, control (C: no additive) and four different P (200, 100, 50, and 25 μg/mL) groups, the final concentration was diluted to 16×106 per straw. Semen samples were equilibrated at 4°C for approximately 4 hours, then placed in French straws and frozen. After thawing, sperm motility and kinetic parameters, DNA integrity by single-cell gel electrophoresis, sperm abnormalities by liquid fixation, and lipid peroxidation levels by the colorimetric method was analyzed by Computer-Assisted Semen Analyzer. P added to the diluent showed no effect on motility and kinetic parameters at P25 and P50 (p>0.05), while P100 and P200 had a negative effect (p⟨0.001). The addition of P (25 and 50) showed a treatment effect on tail abnormality compared to C (p⟨0.05). Especially P50 had a positive effect on tail length, tail DNA, and tail movement, while P100 and P200 caused DNA damage (p⟨0.001). MDA levels increased in all P dose groups compared to C (p⟨0.001). This study has clearly demonstrated that P25 and P50 supplements could be used therapeutically to treat sperm tail abnormalities and prevent DNA damage in post-thawed bull sperm.