Synchronization of cyclic and acyclic embryo recipient mares with donor mares.

The research explores how hormone treatments given to mares during different stages of their reproductive cycle can impact uterine conditions and pregnancy rates after embryo transfer. The study found that certain treatments could improve synchronization with donor mares, potentially increasing the success of embryo transfer programs.

Study Design and Treatments

• This study involved 160 mares divided equally into 8 groups based on their reproductive cycle stage: anestrus, spring transition, early estrus, estrus, diestrus, and early diestrus. The study also used a control group with spontaneous ovulation.
• The groups were subjected to different hormone treatments including dinoprost and estradiol-17β, with the timing of these treatments varying based on each mare’s ovulatory cycle.
• On the start day (Day-4) of the treatment, groups 2 through 7 were given a combination of dinoprost and estradiol-17β, and the estradiol-17β treatment was repeated on Days-3,-2, and -1. Additionally, these mares received long-acting altrenogest on Day0.
• Group 8 received a similar treatment but had an additional dose of dinoprost on Day-3.

Embryo Transfer and Pregnancy Rate Assessment

• Each mare underwent an embryo transfer procedure between three to eight days after the altrenogest treatment.
• Immediately before the embryo transfer, the mare received a boost of altrenogest, and the researchers assessed their uterine features.
• Pregnancy checks were conducted at intervals (7, 30, 60, and 120 days after the transfer), and the pregnant mares received weekly injections of LA-P4 until the 120-day mark.

Results and Implications

• The study found that groups 1 to 6 and group 8 displayed uterine edema and satisfactory pregnancy rates over 65%. This was a positive result, suggesting good synchronization with donor mares.
• Group 8, which received an additional dose of dinoprost, had higher uterine edema scores and pregnancy rates than group 7. This outcome suggests that extra dinoprost dose enhanced the luteolysis process and estrogen response, leading to improved uterus condition and higher pregnancy rates.
• The research concludes that the hormone treatments used in the study are beneficial to synchronize embryo recipient mares with donor mares. This could lead to improved management strategies for embryo transfer programs, potentially increasing their success rate.