Stallion Sperm Freezing with Different Extenders: Role of Antioxidant Activity and Nitric Oxide Production.
Authors: Boni Raffaele, Ruggiero Raffaella, Di Palma Tommaso, Ferrara Maria Antonietta, Preziosi Graziano, Cecchini Gualandi Stefano
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Cryopreservation remains a major limiting factor in equine reproductive management, with marked individual variation in how well stallion semen tolerates freezing protocols. Boni and colleagues collected semen from ten stallions and evaluated three transport extenders followed by four freezing extenders, measuring sperm motility parameters, mitochondrial membrane potential, hydrogen peroxide accumulation, antioxidant capacity (via ABTS and FRAP assays), and nitric oxide metabolites before and after cryopreservation. Whilst extender type did not significantly influence post-thaw sperm function across the cohort, considerable differences emerged in antioxidant activity and nitric oxide production within extenders after freezing; notably, seminal plasma antioxidant activity and nitric oxide levels correlated with refrigerated sperm kinetics and mitochondrial function, but these relationships disappeared following freezing. The findings suggest that individual stallion variation in cryotolerance may relate to inherent differences in oxidative status and nitric oxide metabolism rather than extender selection alone, highlighting the need for individualised assessment protocols and potentially opening avenues for targeted antioxidant supplementation strategies tailored to each stallion's biochemical profile.
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Practical Takeaways
- •Individual stallion variation in freezing tolerance is substantial and cannot be overcome by extender selection alone; testing individual stallions' responses is warranted
- •Seminal plasma antioxidant status and nitric oxide metabolism may serve as useful biomarkers for predicting cryopreservation success in refrigerated semen, though not in frozen samples
- •Focus breeding soundness evaluation efforts on identifying stallions with superior intrinsic antioxidant defenses rather than relying on extender optimization
Key Findings
- •Significant variability in antioxidant activity and nitric oxide content existed among blank extenders and seminal plasma samples
- •Antioxidant activity and NOx values in seminal plasma correlated with sperm kinematic parameters and mitochondrial membrane potential in refrigerated but not frozen semen
- •Sperm function varied significantly between individual stallions but not between extenders before or after freezing
- •Extenders conditioned following freezing showed significant differences in antioxidant activities and NOx values, suggesting post-freeze oxidative changes