Improvement of attachment rate of bovine embryos after transfer with trophoblastic fragments

Fragments of trophoblastic vesicles have been shown to improve embryo development when used in co-culture. We wished to investigate the effect of trophoblastic fragments on establishment of pregnancy after embryo transfer. Embryos (n=129) frozen by direct immersion in liquid nitrogen (Group 1), 82 embryos frozen by the slow freezing method (Group 2) and 55 fresh embryos stored at 20-22 degrees C for 21-22 h (Group 3) were transferred into recipient heifers. The embryos of each group were divided in 2 batches. Batch 1 embryos (control) were transferred without trophoblastic fragments, Batch 2 embryos of each group (experimental) were transferred in combination with frozen-thawed trophoblastic fragments at a rate of 5 to 7 fragments per embryo. The fragments were produced from 16-17 day bovine embryos frozen by vitrification. Two months following the embryo transfers it was established that the attachament rate for Batch 1 embryos in Groups 1, 2, 3 was 33%, 39% and 48%, respectively; for Batch 2 embryos in the same Groups the rate was 55%, 56% and 74%, respectively. We conclude that trophoblastic fragments promote embryo attachment, but their effect does not continue beyond the time of attachment.