Field fertility of liquid stored and cryopreserved flow cytometrically sex-sorted stallion sperm.
Authors: Gibb Z, Grupen C G, Maxwell W M C, Morris L H A
Journal: Equine veterinary journal
Summary
# Editorial Summary: Sex-sorted stallion sperm fertility in field conditions Reproductive technologies enabling sex selection in horses remain underutilised in commercial breeding programmes, largely because current processing methods compromise sperm function and embryo viability. Gibb and colleagues evaluated optimal liquid storage conditions prior to sex-sorting and assessed conception rates following sex-sorting and cryopreservation in a controlled field trial, using nine stallion ejaculates for in vitro assessment and semen from four stallions for insemination into 23 mares. Skimmed milk-based diluents significantly outperformed albumin-based media for maintaining progressive motility, sperm viability and acrosomal integrity during the 18-hour storage period; seminal plasma removal had minimal protective effect at the concentrations tested. Although conception rates following low-dose hysteroscopic insemination were amongst the highest reported for sex-sorted, cryopreserved semen (demonstrating technical feasibility), a notably high rate of early pregnancy loss in both processed-semen groups indicated that embryonic development was substantially compromised despite successful fertilisation—suggesting the cumulative stress of sorting, cooling and cryopreservation impairs gamete quality beyond measures captured by standard motility and viability assessments. For practitioners considering sex-sorted semen programmes, these findings emphasise that further optimisation of sperm handling protocols is essential before commercial application can be reliably recommended, and that current field results warrant cautious interpretation given the significant embryonic wastage observed.
Read the full abstract on PubMed
Practical Takeaways
- •If using sex-sorted stallion semen in your breeding program, expect high early pregnancy loss rates despite acceptable conception rates—embryo viability is compromised by processing.
- •Skimmed milk-based extenders outperform BSA-based media for pre-sorting semen storage, which should inform your semen collection and preparation protocols.
- •Current sex-sorting and cryopreservation technology produces viable conceptions but with unacceptable pregnancy loss; consider this when planning breeding schedules and managing client expectations.
Key Findings
- •Skimmed milk-based media (KMT) was superior to BSA-based media (I-BSA) for maintaining sperm motility, viability, and acrosome integrity during liquid storage.
- •Conception rates with sex-sorted cryopreserved stallion sperm were among the highest reported, but showed no significant difference between treatment groups.
- •High incidence of pregnancy loss occurred in both cryopreserved groups, indicating sperm processing treatments significantly impaired embryonic development.