title: Effect of timing of progesterone administration on pregnancy rate after embryo transfer in ovariectomized mares.
abstract: 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.
mesh_terms: D000818:Animals; D004624:Embryo Transfer / Q000662:veterinary*; D005260:Female; D006736:Horses / Q000502:physiology*; D010052:Ovariectomy; D010060:Ovulation; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects*; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D011374:Progesterone