Hysteroscopic insemination of low numbers of flow sorted fresh and frozen/thawed stallion spermatozoa.
Authors: Lindsey A C, Schenk J L, Graham J K, Bruemmer J E, Squires E L
Journal: Equine veterinary journal
Summary
# Editorial Summary: Flow-Sorted Stallion Spermatozoa and Hysteroscopic Insemination Lindsey and colleagues investigated whether flow cytometric sorting and cryopreservation affected the fertility of stallion semen when used for hysteroscopic insemination, a particularly relevant question for breeders seeking sex-selected or genetically superior genetics. Using a controlled 2×2 factorial design across 41 synchronised mares, they compared pregnancy outcomes following insemination with fresh unsorted sperm (40.0%), fresh flow-sorted sperm (37.5%), frozen unsorted sperm (37.5%), and frozen flow-sorted sperm (13.3%), all standardised to ~5 million motile spermatozoa per insemination. The notable finding was that pregnancy rates remained broadly comparable across the first three treatments, but the frozen flow-sorted group showed a concerning trend towards reduced fertility (P = 0.12), suggesting the combination of sorting and freezing may compromise sperm viability in ways that unsorted cryopreserved semen does not. Whilst hysteroscopic insemination itself performed adequately across groups, practitioners should be cautious about using flow-sorted frozen semen until larger-scale studies determine whether processing conditions, thawing protocols, or selection methodology can be optimised to recover fertility in this challenging category.
Read the full abstract on PubMed
Practical Takeaways
- •Flow sorting stallion semen does not improve pregnancy rates when using fresh spermatozoa, so the additional processing cost may not be justified for fresh semen breeding programs
- •Frozen/thawed flow sorted semen showed reduced fertility compared to other treatments, suggesting the combination of sorting and cryopreservation may be detrimental and warrants further investigation before clinical use
- •Hysteroscopic insemination with low sperm numbers (5×10⁶ motile) achieved reasonable pregnancy rates (37.5-40%) with fresh or frozen/thawed nonsorted semen, offering a practical option for semen conservation
Key Findings
- •No significant differences in pregnancy rates between fresh nonsorted (40.0%), fresh flow sorted (37.5%), frozen/thawed nonsorted (37.5%), and flow sorted frozen/thawed spermatozoa (13.3%)
- •Pregnancy rates tended to be lower (P=0.12) following insemination of frozen/thawed flow sorted spermatozoa
- •Hysteroscopic insemination of 5×10⁶ motile spermatozoa achieved pregnancy rates of 37.5-40% with fresh or frozen/thawed nonsorted semen