Effect of potential oocyte transport protocols on blastocyst rates after intracytoplasmic sperm injection in the horse
Authors: Foss R., Ortis H., Hinrichs K.
Journal: Equine Veterinary Journal
Summary
Intracytoplasmic sperm injection (ICSI) offers a valuable option for breeding from subfertile mares and stallions with compromised sperm reserves, yet its requirement for specialist equipment and technical expertise limits accessibility across equine practice. Foss and colleagues investigated whether immature oocytes and those collected from dominant follicles post-deslorelin stimulation could be transported safely to centralised ICSI facilities by comparing blastocyst development rates under various transport conditions. Dominant stimulated follicle oocytes maintained in sealed tubes at 37°C in pre-equilibrated medium achieved blastocyst rates of 70%—equivalent to non-transported controls—whilst the same oocytes held in passive warm devices yielded only 10%; immature oocytes transported in commercial embryo holding medium at room temperature for up to two nights produced 35–37% blastocyst development. The findings suggest that referring veterinarians could collect immature oocytes using standard transvaginal ultrasound-guided aspiration and send them to ICSI laboratories using readily available holding media without substantial loss of developmental potential, though dominant stimulated follicles require stricter temperature control and are less forgiving of transport delays due to their advanced maturation stage. This practical advancement removes a significant barrier to ICSI application, potentially making the technique accessible to more breeding programmes by decentralising oocyte collection from the requirement for on-site laboratory facilities.
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Practical Takeaways
- •Referring veterinarians can now collect immature oocytes and ship them at room temperature using commercial embryo holding medium, enabling access to ICSI technology without on-site laboratory facilities
- •Dominant stimulated follicle oocytes require maintenance at 37°C during transport to achieve optimal blastocyst rates (70%), whereas immature oocytes are more flexible (35-37% success at room temperature)
- •This makes ICSI more practical and widely accessible for breeding programs using stallions with limited sperm or subfertile mares
Key Findings
- •Dominant stimulated follicle oocytes in sealed tubes with pre-equilibrated maturation medium at 37°C achieved 70% blastocyst development equal to control incubated oocytes
- •Immature oocytes held in modified M199 medium or commercial embryo holding solution at room temperature yielded 35-37% blastocyst development
- •Dominant stimulated follicle oocytes in warm passive devices yielded only 10% blastocyst development
- •Both immature and mature oocytes can be successfully transported for ICSI using appropriate protocols