Effects of the cryotop vitrification method for the cryopreservation of in vitro produced Cỏ goat embryos

This study investigated the influence of embryonic developmental stage, cryoprotectant concentration, and vitrification solution volume on the cryopreservation efficiency of in vitro-produced Cỏ goat embryos. In Experiment 1 the survival rate of zygotes cryopreserved 20 h after IVF was lower than blastocysts cryopreserved 7 days after IVF (66.86 % vs 90.92 %, P < 0.05). The cleavage and blastocyst rates of the zygote group were lower than those of the control (non-cryopreserved) group (52.91 % and 81.94 % vs 81.94 % and 36.48 %, respectively, P < 0.05). The hatching blastocyst rate achieved by embryos vitrified as blastocyst or zygotes was 14.62 % and 3.69 %, respectively. In Experiment 2, the survival rate of blastocysts vitrified in the 16.5 % EG + 16.5 % DMSO group was higher than that of the 12.5 % EG + 12.5 % DMSO and 20 % EG + 20 % DMSO groups (91.34 % vs 43.16 % and 61.24 %, respectively, P < 0.05). The hatching blastocyst rate of 12.5 % EG + 12.5 % DMSO, 16.5 % EG + 16.5 % DMSO and 20 % EG + 20 % DMSO groups was 0 %; 13.74 % and 0 %, respectively. In Experiment 3, the difference in the survival rate between blastocysts vitrified in 0.3 μL, 0.5 μL and 1 μL was not statistically significant (P > 0.05). The hatching blastocyst rate of the 0.3 μL group was higher than that of the 0.5 μL and 1 μL groups (44.18 % vs 13.98 % and 14.36 %, respectively, P < 0.05). In conclusion, the IVP Cỏ goat embryos were successfully vitrified by cryotop vitrification method at a CPA concentration of 16.5 % EG + 16.5 % DMSO with a vitrification solution volume of 0.3 μL.