Factors influencing success of embryo transfer in sheep and goats

The results of embryo transfers from 130 donor Angora goats and 60 sheep of 3 breeds are presented, and the data analyzed to determine some of the sources of variation in success rate. Of all adult donor goats programmed, 94.9% yielded embryos suitable for transfer and 93.4% yielded offspring from the transfers. Donor ewes yielded percentages of 76.8 and 46.7, respectively. Fertilization failure and/or degeneration of embryos in donors prior to flushing accounted for the lower recoveries of viable embryos from sheep, the incidence of both being greater in donors with higher ovulation rates. High ovulation rate of donors also decreased percentage survival of sheep but not goat embryos after transfer. Stage of embryo development, site of transfer (oviduct vs. uterus) or number of embryos transferred (1 vs. 2) per recipient did not affect survival of sheep embryos following transfer to appropriately synchronized recipients. In goats, survival was significantly better with two than with one embryo transferred per recipient. Super-ovulation failure and poor fertilization limited the yield of embryos obtained from donor goats and sheep less than 1 year of age. These could be overcome to some extent by use of progestagen sponge rather than prostaglandin in the superovulation treatment regimen.