Ultrastructural characterization of fresh and cryopreserved in vivo produced ovine embryos

P =0.02), and a significant higher number of grade 3 blastocysts was found at semithin sectioning after OPS vitrification ( P =0.037). The extension of ultrastructural damage, especially of mitochondria and cytoskeleton, was related to the semithin classification but not to stereomicroscopical scoring at thawing. This suggests that semithin scoring is a useful tool for predicting ultrastructural lesions and new improvements in cryopreservation and thawing methods of ovine embryos are still warranted, including in the case of blastocysts cryopreserved by OPS vitrification.

Cryopreservation; OPS vitrification; Ovine embryo morphology; Ultrastructure