Towards increasing stallion sperm longevity by storage at subzero temperatures in the absence of ice.
Authors: Pruß David, Oldenhof Harriëtte, Wolkers Willem F, Sieme Harald
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Supercooled Storage of Stallion Semen Extending semen viability between refrigeration (5°C, several days) and full cryopreservation (decades, but with significant freeze-thaw damage) remains a significant challenge in equine reproduction. Prüss and colleagues investigated whether stallion sperm could be maintained at –10°C in a supercooled, unfrozen state by adding 2% Ficoll-400 and mineral oil overlay to prevent ice crystal formation, comparing this approach against conventional 5°C storage over seven days. The researchers achieved non-frozen samples in approximately 40% of supercooled specimens at 50×10⁶ sperm mL⁻¹, and demonstrated that 100 mM sucrose preserved sperm membrane integrity during –10°C storage, though membrane-intact sperm percentages remained lower than refrigerated controls; critically, whilst progressive motility was largely lost during supercooled storage, partial restoration occurred when switching from buffered saline to milk-based extenders. For practitioners seeking intermediate storage options—particularly useful for stallions with limited semen supply or when fresh semen transport is logistically challenging—supercooled storage presents a promising bridge technology, though further refinement of extender formulations is needed to reliably preserve motility alongside membrane integrity.
Read the full abstract on PubMed
Practical Takeaways
- •Supercooled storage at -10°C without ice formation shows potential as an intermediate preservation method between refrigeration (5°C) and cryopreservation, potentially extending storage duration beyond current refrigerated protocols
- •Further optimization of storage solutions is needed to maintain sperm motility during supercooled storage before this technique can be applied clinically in breeding programs
- •This technology may offer advantages over traditional cryopreservation by avoiding freeze-thaw damage, but current protocols still result in viability losses that require additional research
Key Findings
- •Addition of 2% Ficoll-400 to buffered saline with mineral oil enabled supercooled storage of stallion sperm at -10°C for up to 7 days without ice formation
- •About 40% of samples with 50×10⁶ sperm mL⁻¹ remained non-frozen during supercooled storage
- •Adding 100 mM sucrose preserved sperm membrane intactness during supercooled storage but resulted in lower percentages than refrigerated storage at 5°C
- •Sperm motility was lost during supercooled storage at -10°C but could be partially restored using milk-based extender as base medium