The aim of this study was to compare the efficiency of three cryopreservation techniques namely, controlled slow freezing, conventional vitrification and open pulled straw (OPS) vitrification, for the cryopreservation of in vivo produced Portuguese Black Merino ovine embryos. Fresh (control group) and cryopreserved embryos (3 methods) were transferred by laparoscopy to recipient ewes (2 embryos/recipient). Embr...