PGF-2 alpha release, progesterone secretion and conceptus growth associated with successful and unsuccessful transcervical embryo transfer and reinsertion in the mare.

This study investigates the growth of foetuses, the secretion of progesterone, and release of the prostaglandin PGF-2 alpha in mares during and after transcervical embryo transfer and reinsertion. The research indicates a pattern of growth, hormone release and subsequent embryo status, finding that the destiny of early conceptus transfers largely depends on procedural factors.

Study Overview and Method

• The research was conducted on 30 mares and evaluated the outcome of 23 collections and reinsertions of embryonic concepts performed between Days 10.5 to 13.5 post ovulation, the transfer of 4 Day-10.5 embryos, and 13 transfers of Day-6.5 embryos.
• The team monitored hormone levels through blood samples taken before and after each procedure. The samples were analyzed for concentrations of the prostaglandin PGF-2 alpha (PGFM), and progesterone, a hormone crucial for maintaining pregnancy.
• In addition, mares underwent daily checks for signs of oestrus, as well as uterine ultrasonography to track conceptus development.

Results and Findings

• After the reinsertions, 12 out of 23 conceptuses were detected immediately. However, after 4 days, only 1 conceptus was found to be successfully developed into a normal foal, while the rest disappeared.
• All Day-10.5 conceptuses transferred disappeared within the following week.
• Of the 13 Day-6.5 conceptuses transferred, 8 were detectable by Day 11.5. Five of these grew into healthy foals, while the remaining three were lost between Days 14 and 25.

Progesterone and PGF-2 alpha Observations

• Small increases in PGFM levels were detected in 8 out of 23 collection-reinsertion procedures conducted on Days 10.5 to 13.5 and after 2 out of 25 Day-6.5 recoveries.
• Significant reductions in progesterone levels were noted within 24 hours of the procedure in only one Day-10.5 transfer case.
• The disappearance of the conceptuses subsequently related with complete luteolysis — the degeneration of the corpus luteum that produces progesterone — in a single Day-6.5 transfer, one Day-10.5 transfer, and one Day-12.5 reinsertion.

Conclusion

This study presents valuable findings on the relationship between procedural factors, hormonal changes, and the success of early conceptus transfers in mares. The results could aid in improving the techniques for embryo transfer and reinsertion procedures in horses, as well as deepening our understanding of hormone activity during early equine pregnancy.