Embryo recovery from the oviduct in superovulated ewes: a method to improve MOET systems

The efficiency of embryo recovery in a superovulatory treatment was studied by perfusing the oviduct or the uterine horn in 3.5 and 7 days after sponge withdrawal, respectively. Eighty-four and seventy ewes of Aragonesa breed were used as embryo donors and receptors, respectively. The donors were distributed in 3 replications. The oestrus was synchronized with the insertion of FGA intravaginal sponges (30 mg) for 13 days. Six intramuscular injections of 18 mg pFSH were applied in decreasing doses at 12 hour intervals starting 48 hours after sponge withdrawal. The recovery rate (RR) (83.2 vs. 75.8%), the viability rate (VR) (73.5 vs. 47.2%) and the number of viable embryos (VE) per donor ewe (5.9 ± 0.79 vs. 3.0 ± 0.37) were higher (P < 0.01) in ewes whose perfusion was done directly in oviducts. The interval from sponge withdrawal to oestrus had no influence on RR in any groups; however it had an effect on the VR in 3.5 and 7 days old embryos. Embryos from ewes showing the oestrus within 20 hours after sponge withdrawal had a higher viability. On the other hand, using morphologic criteria, 26.5% and 52.7% of 3.5 and 7 days old embryos, respectively, were discarded before transfer. The percentage of ewes in each group that became pregnant was similar in both groups. We conclude that in superovulated ewes the embryo recovery rate, viability and number of viable embryos are higher in embryos recovered from the oviduct compared to those recovered from the uterus, without decreasing the conception rate and the viability rate is higher in ewes that show the oestrus 20 hours before sponge withdrawal.