Autotransfer of Day 4 embryos from oviduct to oviduct versus oviduct to uterus in the mare.

The research paper investigates procedures and success rates of embryo autotransfer in mares, an operation in which an embryo is both retrieved and reinserted into the same animal’s body. The results support the idea that transport of the embryo from the oviduct to the uterus isn’t reliant on a one-sided embryo-corpus luteum interaction, and that Day 4 embryos can survive in the mare’s uterus.

Objective of the Study

The paper has three main objectives:

• Test the hypothesis that the transportation of the equine embryo from the oviduct to the uterus is not dependent on a unilateral interaction between the embryo and corpus luteum.
• Develop a technique for embryo autotransfer in mares.
• Compare the success rates of Day 4 embryos surgically autotransferred from the ovulating side oviduct to either the opposite side oviduct or uterine horn.

Methodology and Findings

The study group was composed of mares from which Day 4 embryos were surgically autotransferred. They were divided into two groups of 10, with one group receiving autotransfers to the oviduct and the other to the uterine horn on the opposite side of ovulation. Findings demonstrated:

• 70% of the Day 4 embryos autotransferred to the oviduct opposite to the side of ovulation successfully travelled through the oviduct and developed into detectable embryonic vesicles between 10 and 21 days after ovulation. This indicated that the embryo’s travel from the oviduct to the uterus did not require ipsilateral corpus luteum interaction.
• Overall, 60% of all autotransfers were successful, suggesting efficacy in the autotransfer approach.

Conclusion

The success rate of embryos transferred to the uterus was not significantly lower than that of embryos transferred to the oviduct (50% vs 70%, respectively). This finding supports the assertion that Day 4 equine embryos ar mature enough to survive in the mare’s uterus, providing a practical implication for equine embryo transfer procedures.