Pregnancy and Luteal Responses to Embryo Reinsertion Following Embryo Flushing in Donor Mares

Abstract

The effect of embryo reinsertion immediately after embryo flushing was studied to determine its effect on luteal function, pregnancy outcome, endometrial bacterial contamination, and embryo morphology. In Experiment 1, eight mares were used during 32 cycles (8 cycles in each group): for the first two groups, inseminated mares were flushed 8 days after ovulation and prostaglandin F2α was not administered: in group EF-ET (embryo flushing and embryo transfer) the embryo was reinserted in the same donor mare, while in the EF group, no further procedure was performed. In the third group (ET), non-inseminated mares (recipients) received a Day 8 embryo 5 to 8 days after ovulation. Progesterone concentration was measured before EF/ET and 72 h after in the 3 groups. Pregnancy diagnosis was performed within 6 days of transfer. In Experiment 2, twelve mares were used during 17 cycles in two groups: EF-ET (n=11) and ET (n=6), as in Experiment 1, except that every mare was flushed 24 h after embryo transfer to retrieve the embryo. Fewer pregnancies resulted after transfer in EF-ET cycles (0(8, 0%) than in the ET group (6/8, 75%). Progesterone concentration decreased significantly (p=0.05) 72 h after EF-ET, but not in EF or ET cycles (p>0.1). Three mares from the EF-ET showed full luteolysis and signs of endometritis. In Experiment 2, more (5/6; p=0.08) grade I embryos were recovered in the ET compared to the EF-ET group (3/7); 4 embryos were graded III-IV (were broken or had signs of degeneration) in the EF-ET group, but none in the ET group. In both groups, capsule fragments were obtained as indicative of the presence of a recently destroyed embryo in the EF-ET (n=3) and ET (n=1) groups. Positive bacterial cultures were obtained in 2/11 and 1/6 embryo flushes from the EF-ET and ET groups, respectively.