Effect of timing of progesterone administration on pregnancy rate after embryo transfer in ovariectomized mares.

This study explores the impact of timing for progesterone administration on pregnancy rates in ovariectomized mares after embryo transfer. The research shows that synchronizing the onset of progesterone administration with donor ovulation significantly increases the chances of successful pregnancy.

Study Design and Methodology

• The researchers divided ovariectomized mares, which are female horses that had their ovaries removed, into two groups – Group A and Group B.
• Group A mares received a daily injection of 300 mg of progesterone in oil starting five days before a 7-day embryo was transferred into them.
• On the other hand, Group B mares were administered the same dose of progesterone, but this was instead started at least four days before the donor’s ovulation.

Determining Pregnancy

• Presence of an embryonic vesicle, which indicates early-stage pregnancy, was determined using ultrasonography.
• The mares were considered to be pregnant if they exhibited normal vesicle development up to Day 18 post the embryo transfer.

Results of the Study

• The study found a significant difference in pregnancy rates between the two groups. Group A recorded 6 successful pregnancies out of 8 mares, while Group B only had 1 successful pregnancy out of 12 mares.
• Furthermore, it was observed that an additional four mares in Group B did initially have a visible vesicle at 14 days, but this either degenerated or did not grow as expected.
• These results suggest a strong correlation between the timing of progesterone administration and successful establishment of pregnancy after embryo transfer in ovariectomized mares.
• The findings in this study indicate that it is significantly beneficial to synchronize donor ovulation with the onset of progesterone administration. This implies that the timing of hormonal intervention has a direct impact on pregnancy success rates.