Effect of Vitrification in Open Pulled Straws on Survival of Bovine Embryos from Superovulated Cows

Bovine embryos (Day 6.5 -7.5 ) collected from superovulated cows were exposed to open pulled straw (OPS) vitrification before in vitro culture for 72 hours.The aim of this cryopreservation study applied to embryos of different developmental stages and morphological quality grades was to assess embryo survival and process of embryo handling during commercial embryo transfer (ET) procedures using the conventional freezing method as a control.During the culture of thawed quality grade 1 embryos, the hatched blastocyst stage was reached by 38.6% (27/70) of the vitrified and by 34.5% (29/84) of the conventionally frozen (control) embryos (p > 0.05).The corresponding proportions for quality grade 2 and 3 embryos were 18.5% (10/54) vs. 5.4% (2/37) and 11.8% (8/68) vs. 2% (1/50), p > 0.05, respectively.Hatching rates of embryos vitrified or conventionally frozen at the morula stage were 35.7% (15/42) and 30.3% (17/56), p > 0.05, respectively.No significant difference was found between hatching rates of embryos vitrified or conventionally frozen at the stage of early blastocysts (29.3%; 12/41 vs. 34%; 18/54).The hatching rates of embryos vitrified or conventionally frozen at the blastocyst and expanded blastocyst stages were 30.8% (12/39) vs. 21.6%(11/51), p > 0.05 and 29.3% (11/37) vs.11.4% (5/44), p < 0.05, respectively.The study demonstrated about the same survival rates for vitrified and conventionally cryopreserved embryos of all quality grades and developmental stages during in vitro embryo culture.Expanded blastocysts survived better vitrification than conventional freezing (p < 0.05).OPS vitrification is an effective and rapid method of cryopreservation of bovine embryos.Bovine embryo, superovulation, cryopreservation, freezing, thawing, vitrification, OPS vitrification