Pregnancy rate after the transfer of sheep embryos originated from randomly chosen oocytes matured and fertilized in vitro

Randomly chosen sheep oocytes isolated from 2- to 5-mm follicles of hormonally nonstimulated slaughtered females were matured and fertilized in vitro. Using heparin for the induction of ram sperm capacitation, a fertilization rate close to 80% was recorded. After the transfer of 29 embryos cultured to the 2- to 4-cell stage to 4 recipients, each delivered 1 lamb. In another experiment, 34 2-cell embryos stage were transferred (1 to each oviduct) to 17 synchronized recipients; 8 pregnancies were established and each of 5 recipients delivered a single lamb. The remaining 3 recipients aborted at the third month of gestation. These results show that sheep embryos can be produced in vitro from randomly chosen oocytes and by using relatively simple procedures. However, the viability of the embryos was low, with approximately only 15% developing to term after transfer at the 2-cell stage.