24-Hour cooled storage of equine embryos.

This research aimed to investigate the viability of equine embryos after 24-hour cooled storage. Researchers found that some embryos survived and were successfully implanted into recipient mares resulting in live foals, although the success rate was lower than with immediately transferred embryos.

Methodology

• The researchers collected equine embryos 7 days after ovulation using a technique known as transcervical uterine flush, which involves the use of a saline-based flushing solution enriched with newborn calf serum and antibiotics (penicillin-streptomycin) to retrieve the embryos.
• Each retrieved embryo was then cleaned with a modified version of the original saline solution, but this time also containing bovine serum albumin, a protein believed to increase embryo viability.
• Following cleaning, the embryos were placed in polystyrene test tubes containing a medium developed from the washing solution. The embryos were kept in these tubes for storage.
• To simulate the conditions of cooled storage, the embryos were placed in a commercial semen transport container, which cooled at a rate of -0.3 degrees Celsius per minute until the temperature reached 4 to 6 degrees Celsius. This cooling process was maintained for 24 hours.

Results

• After the 24-hour chilled storage period, 16 embryos were transferred into recipient mares.
• Two weeks after the transfer, six of the 16 embryos were detected as growing vesicles – a sign of a successful implantation – using ultrasound technology. This indicates a 37.5% success rate after the cooled storage period.
• Of these six, three proceeded to full term pregnancies, resulting in the birth of three live, healthy foals, a live birth rate of 18.75%.
• In order to assess the effectiveness of cooled storage, the researchers also included a control group. This group consisted of 16 embryos that were transferred directly into the recipient mares without any prior storage. Five foals resulted from these transfers, a live birth rate of 31.25%, significantly higher than that of the cooled storage method.

Conclusion

• The study provides evidence that equine embryos can survive a 24-hour period of cooled storage. However, the success rate for transfer and live births was lower for embryos held in cooled storage compared to those immediately transferred.
• This research could have implications for equine reproduction practices, particularly in situations where immediate transfer of embryos is not possible, or in programmes aimed at the conservation of endangered equine species.