Importance of gestation losses after non-surgical transfer of cultured and non-cultured bovine blastocysts.

Several techniques, including progesterone assay at days 21, 28 and 35, heat detection twice daily, rectal palpation at day 60 or planned slaughter, were combined to determine the importance of gestation losses after a single cervical transfer of 128, 10 to 12-day-old bovine embryos. Using non-cultured embryos (n = 83) transferred within six hours after recovery, 29.3 per cent of the initiated gestations were lost before day 60. Few abortions occurred after that stage. More than 50 per cent of the losses concerned preimplantation embryos from day 21 to day 35. When embryos cultured for 24 hours at 37 degrees C were used, there was a marked increase in the gestation loss (46.3 per cent) occurring mainly at the time of implantation. This suggests that the culture had a detrimental effect on the embryonic disc cells.