Slow Cooling is Beneficial for Storage of Frozen-Thawed Equine Spermatozoa.
Authors: van Heule Machteld, Verstraete Margo, Blockx Zoé, De Blende Peter, Dini Pouya, Daels Peter
Journal: Journal of equine veterinary science
Summary
# Slow Cooling Improves Post-Thaw Semen Storage in Horses When frozen equine semen is thawed at a breeding facility, the ability to cool-store it briefly before use or transport opens significant practical advantages—allowing on-site evaluation, quality control, and flexible logistics in breeding programmes. Researchers compared two post-thaw cooling protocols across 31 semen samples: rapid cooling in a passive cooling box versus a modified approach involving 30 minutes at 4°C in a refrigerator before transfer to the passive box, measuring total and progressive motility and viability at intervals up to 24 hours. The refrigerator pre-cooling protocol substantially outperformed passive cooling alone during the critical first 8 hours, preserving total motility (only 0% decline versus 8.12% loss) and progressive motility similarly to baseline, whilst passive cooling showed significant deterioration (8.52% progressive motility loss by 8.5 hours). Beyond 24 hours, both methods resulted in unacceptable viability losses (approximately 12–13.5%), making extended storage impractical regardless of technique. Whilst individual stallion variation suggests this protocol won't benefit all horses equally, the 30-minute refrigeration step represents a worthwhile refinement for centres managing thawed semen, particularly where on-site assessment or short-distance transport is required; however, practitioners should establish whether their stock responds favourably before relying on this window for clinical decision-making.
Read the full abstract on PubMed
Practical Takeaways
- •A brief 30-minute refrigeration step at 4°C before passive cooling can improve sperm survival during the critical first 8 hours post-thaw, supporting on-site evaluation and shipping logistics
- •Frozen semen should be used within 8 hours when using the refrigeration pre-treatment protocol; beyond 24 hours, significant quality loss occurs regardless of method
- •When implementing slow cooling protocols, monitor individual stallion response as some may not tolerate this method well—establishing baseline quality for each stallion is recommended
Key Findings
- •Refrigeration at 4°C for 30 minutes before passive cooling preserved total and progressive motility during 8-hour storage, with no significant reduction compared to baseline (T0 and T8-REF similar)
- •Immediate passive cooling resulted in significant motility loss of 8.12% total and 8.52% progressive motility by 8 hours
- •Both storage protocols showed significant motility and viability decline by 24 hours, with viability losses ranging from 9.65% to 13.52%
- •Individual variation between stallion samples suggests that slow cooling protocols may not be universally suitable for all individuals