An Investigation of Equine Sperm Quality Following Cryopreservation at Low Sperm Concentration and Repeated Freeze-Thawing.
Authors: Morse-Wolfe Bethany, Bleach Emma, Kershaw Claire
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Low-Concentration Stallion Sperm Cryopreservation and Repeated Freezing Advances in assisted reproductive technologies like intracytoplasmic sperm injection (ICSI) have created an opportunity to reduce semen wastage by cryopreserving stallion ejaculates at lower concentrations than the current industry standard of 200–300 million sperm/ml. Morse-Wolfe and colleagues investigated whether dropping sperm concentration and subjecting samples to multiple freeze-thaw cycles would compromise post-thaw semen quality in good freezer stallions, assessing total and progressive motility, viability, acrosome integrity and oxidative stress across eight concentration treatments (5–400 million sperm/ml) in the first experiment, and evaluating refrozen samples in the second. The key finding was that concentrations between 50–400 million sperm/ml maintained equivalent post-thaw total motility, progressive motility and viability; however, dropping to 5–20 million sperm/ml resulted in significant losses, and both refreezing and low-concentration preservation caused measurable declines in motility and viability by the second thaw cycle. For practitioners managing genetically valuable stallions, these results support moving to 50 million sperm/ml as a sustainable lower threshold without sacrificing post-thaw quality, though refreezing protocols require further refinement before becoming routine practice.
Read the full abstract on PubMed
Practical Takeaways
- •For breeding programmes using ICSI or similar techniques, stallion semen can be safely cryopreserved at 50 million/ml or higher without loss of post-thaw quality, potentially reducing waste when only one or few sperm are needed per procedure
- •Refreezing thawed semen is not recommended as it significantly compromises sperm quality; plan thaw volumes carefully to minimize need for refreezing
- •Genetically valuable stallions with good freezing characteristics may allow lower concentration preservation protocols, maximizing utilization of limited ejaculates
Key Findings
- •Sperm concentrations between 50-400 million/ml maintained post-thaw total and progressive motility and viability equally well in good freezer stallions
- •Concentrations of 5-20 million/ml resulted in significantly reduced post-thaw motility and viability compared to higher concentrations
- •Both refreezing and reduction of sperm concentration decreased motility, progressive motility and viability after two freeze-thaw cycles
- •Spermatozoa cryopreserved at 20 million/ml maintained some motility and viability even after two freeze-thaw cycles, though suboptimally