Abstract :
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 cryopreservedembryos (3methods)were transferred by
laparoscopy to recipient ewes (2 embryos/recipient). Embryo survival rates were assessed
and pregnancy diagnosis was performed by serum progesterone concentration on day 18
and by ultrasonography on day 45, and at lambing. Successful pregnancy and embryo survival
rates did not differ between the fresh (73.3 and 50.0%, respectively) and cryopreserved
(58.3 and 38.5%, respectively) embryos.No differences in lambing and embryo survival rates
were observed between the three cryopreservation methods used (68.4 and 44.7%; 50.0
and 33.3%; 54.5 and 36.3% for controlled slow freezing, vitrification and OPS, respectively).
Pregnancy rate based on serum progesterone concentration on day 18 was higher than the
pregnancy diagnosed at 45 days following transfer for the cryopreserved embryos. It could
be concluded that all three cryopreservation techniqueswere equally efficient in preserving
and propagating genetic material in Portuguese Black Merino sheep
