Ovum pick-up in sheep: Efficiency of in vitro embryo production, vitrification and birth of offspring

The production of offspring involving available technologies like ovum pick -up, in vitro embryo production and cryopreservation has not been fully des cribed in the sheep. We tested the overall efficiency of these procedures o n 20 Sarda dairy ewes that were twice stimulated for recovery of follicular oocytes. In total, 415 oocytes were aspirated from 522 follicles (11.5 ooc ytes/ewe), and 328 of them (9.1 oocytes/ewe) were selected for in vitro emb ryo production procedure. Development into blastocysts occurred in 98 embry os (2.7 blastocysts/ewe), of which 64 were vitrified and 34 were transferre d, in pairs, directly to recipients. The pregnancy rate, diagnosed at 80 d for fresh and vitrified embryos, did not differ significantly (47.1 vs 42.8 %, respectively), but there were significant differences in lambing rates b etween the 2 groups (41.2 vs 23.8%, respectively). Overall, 24 lambs were b orn; all weighed within the range for the breed, but head deformities were observed in 2 cases. The results of this study show that with application o f the above techniques, it is possible to obtain repeatedly embryos and via ble offspring. (C) 1999 by Elsevier Science Inc.