Effect of timing of progesterone administration on pregnancy rate after embryo transfer in ovariectomized mares. Academic Article uri icon


  • Ovariectomized recipient mares were divided into two groups. Group A mares received 300 mg progesterone in oil i.m. daily starting 5 days before transfer of a 7-day embryo. Group B mares received the same dose of progesterone, but starting at least 4 days before donor ovulation. Presence of an embryonic vesicle was determined by ultrasonography; mares were considered to be pregnant if they had normal vesicle development to Day 18. Pregnancy rates were: Group A, 6/8; Group B, 1/12 (P less than 0.01). An additional 4 mares in Group B had a vesicle visible at 14 days which degenerated or did not grow. These results indicate that, for establishment of pregnancy after embryo transfer, there is a need for synchrony of donor ovulation with onset of progesterone administration to ovariectomized recipient mares.

published proceedings

  • J Reprod Fertil Suppl

author list (cited authors)

  • Hinrichs, K., & Kenney, R. M.

citation count

  • 15

complete list of authors

  • Hinrichs, K||Kenney, RM

publication date

  • January 1987