Effect on equine sperm of post-thaw glycerol dilution using two different semen extenders.
Authors: Otero J C, Neild D M, Ferrante A A, Gambarotta M C, Caldevilla M L
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Post-Thaw Glycerol Dilution in Equine Semen Glycerol, whilst essential for cryopreserving equine spermatozoa, inflicts considerable cellular damage through osmotic stress and lipid membrane disruption. Otero and colleagues investigated whether post-thaw dilution could mitigate these effects by re-diluting frozen semen (originally preserved with 5% glycerol) at a 1:2 ratio in either Tyrode's solution or a commercial equine extender, then evaluating multiple sperm parameters—motility, membrane integrity, acrosomal status, oxidative damage and DNA fragmentation—across nine stallion samples. Surprisingly, neither extender produced improvements in total or progressive motility (remaining around 40–43% and 27–30% respectively) or reduced oxidative or genetic damage; however, the commercial extender yielded a meaningful advantage by preserving significantly more sperm with intact plasma membranes and acrosomes (39.4% versus 33.5–33.9% in controls and Tyrode's). For practitioners utilising frozen equine semen, these results suggest that post-thaw dilution alone offers limited benefit for fertility-critical parameters like motility, yet the commercial extender's protective effect on acrosomal integrity warrants consideration, as premature acrosomal reaction represents a significant barrier to conception and fertilisation success.
Read the full abstract on PubMed
Practical Takeaways
- •Post-thaw glycerol dilution using a commercial equine extender may help preserve sperm membrane and acrosome integrity when thawing frozen semen for breeding
- •Standard motility parameters alone do not reflect improvements in sperm membrane quality; practitioners should consider membrane integrity assessments when evaluating frozen semen quality
- •Using a commercial equine extender for post-thaw dilution appears preferable to Tyrodes buffer for maintaining acrosome status in thawed equine semen
Key Findings
- •No significant differences in total motility (TM 41-43.8%) or progressive motility (PM 27.5-30.6%) between control and either post-thaw extender treatment
- •Commercial equine extender (CE) produced significantly higher percentages of sperm with intact plasma membranes and acrosomes (39.4%) compared to control (33.9%) and Tyrodes (33.5%)
- •DNA fragmentation and lipid peroxidation showed no significant differences between post-thaw dilution treatments and control
- •Post-thaw dilution with CE may reduce the proportion of sperm with reacted acrosomes, potentially benefiting fertility outcomes