PGF-2 alpha release, progesterone secretion and conceptus growth associated with successful and unsuccessful...

The outcome of 23 collections and reinsertions of conceptuses on Days 10.5-13.5, 4 transfers of Day-10.5, and 13 transfers of Day-6.5 embryos (ovulation = Day 0) was monitored in 30 mares. Blood samples were taken before and after each procedure to measure plasma 15-keto-13,14-dihydroprostaglandin F-2 alpha (PGFM), and then daily for progesterone determinations. Mares were also subjected to daily teasing for detection of oestrus, and to uterine ultrasonography for tracing the development of the conceptus. After the reinsertions, 12/23 conceptuses were detectable immediately after the procedure. Of these, 1 developed into a normal foal but 11 disappeared during the next 4 days. All 4 Day-10.5 conceptuses transferred disappeared within 7 days. Of the 13 Day-6.5 conceptuses transferred, 8 were detectable by Day 11.5 and 5 of these developed into healthy foals. The 3 losses occurred between Days 14 and 25. Small increases in PGFM concentrations occurred in 8/23 collection-reinsertion procedures on Days 10.5-13.5 and after 2/25 Day-6.5 recoveries, but during none of the 13 Day-6.5 transfers. A marked reduction (greater than or equal to 40%) in progesterone concentration was noted within 24 h of the procedures in only one Day-10.5 embryo transfer and, in subsequent days, the disappearance of the conceptuses was associated with complete luteolysis in only 1 Day-6.5 transfer, 1 Day-10.5 transfer and 1 Day-12.5 reinsertion.(ABSTRACT TRUNCATED AT 250 WORDS)