Pregnancies after transfer of sheep embryos produced from oocytes matured and fertilized in vitro.

The experiments describe simple and effective methods used for the production of sheep embryos in vitro. The oocytes isolated from the ovarian follicles, 2-5 mm in diameter, were matured in culture for 22-24 h. After mixing with ram spermatozoa pretreated with heparin, 77-100% of fertilized oocytes were monospermic. Some of them (60-68.3%) cleaved in culture after 24-50 h to 2-4-cell stage. The transfer of cleaved embryos to the oviducts of 4 synchronized recipients resulted in pregnancies and 4 normal lambs were born at term.