Cinnamaldehyde as a Natural Antimicrobial in Donkey Semen: Efficacy and Sperm Cytotoxicity

Bacterial contamination of donkey semen samples is a major concern due to its deleterious effects on sperm quality; this issue is exacerbated during semen storage. Therefore, evaluating the effect of antimicrobials on sperm is of utmost importance. This study identified microorganisms present in donkey semen and evaluated the antimicrobial activity of cinnamaldehyde, determined by the Minimum Inhibitory Concentration (MIC), and its effects on sperm quality. Fourteen semen samples from seven donkeys were analysed, identifying 31 bacterial isolates representing 21 different species. Cinnamaldehyde showed antimicrobial activity (MIC₅₀ = 0.06 mg/mL; MIC₉₀ = 4 mg/mL). Reactive oxygen species levels in sperm were decreased, suggesting an antioxidant effect. However, high concentrations of cinnamaldehyde reduced sperm motility. In conclusion, cinnamaldehyde is a promising antimicrobial for semen preservation; however, further studies are needed to ensure antimicrobial efficacy and sperm functionality.