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The selection of quality embryos is a prerequisite of cryopreservation process. Present study was conducted to examine the correlation between the diameter and cryotolerance, on the cell number of the cryopreserved embryos. The blastocyst stage embryos were collected at culture days 7–9, evaluated morphologically under a microscope and divided according to the diameter into three groups: Group 1; (larger than 150 μm), Group 2; (diameter of 100–150 μm), Group 3; (smaller than 100 μm). Blastocysts were vitrified-thawed using the classical vitrification method and then cultured in SOF medium drops at 24 h. Blastocysts were considered viable if they re-expanded or hatched from the zona pellucidae. Finally re-expanded blastocysts from the Group 1 and Group 2 to determine the differential count of cells in the ICM and TE. The re-expansion ability of blastocysts 100–150 μm in diameter (69.56%) was significantly higher than other groups (52.17 and 47.36%). The value of the correlation coefficient between the re-expansion rate and cell number of blastocysts in the group 2 (r = 0.784) tended to be higher than that in the group 1 (r = 0.512) and group 3 (r = 0.491) (p < 0.05). For ICM/total cell ratio yield group 2 embryos showed higher rate (0.28), compared to the other groups (0.19 and 0.16). In conclusion, the present study demonstrates that the correlation between diameter of embryos and their cryosurvival based on re-expansion ability and cell allocation. [ABSTRACT FROM AUTHOR]

The present study examined the developmental capacity and cryotolerance of cultured bovine embryos in defined media (synthetic oviduct fluid, SOF) supplemented with insulin-like growth factor I (IGF-I) and leukemia inhibitor factor (LIF). The objectives of the present study were: (1) to examine the effects IGF-I and LIF on bovine embryo development potential and (2) to investigate the cryotolerance and survivability of vitrified blastocysts obtained from embryos cultured in a defined media. We studied the development of bovine embryos produced in vitro and cultured (in four different treatments) until Day 7 after fertilization. In Experiment 1, zygotes were cultured to the blastocyst stage and differentially stained for determine the count of cells. In Experiment 2, zygotes were vitrified before staining. LIF alone or combined with IGF-I was significantly effective on in vitro bovine embryo development especially ratio to reach blastocyst. The cells for both ICM and TE decreased by the effect of freezing in all treatment groups in the Experiment 2 compared with Experiment 1. Interestingly, the LIF treatment showed fewest variations. In addition to this, for average number of ICM and TE cells, LIF treatment showed fewest variation compared with other treatments (ICM: 23.5 vs 19.5, TE: 53.6 vs 51). These results are the first to demonstrate that the addition of IGF-I along with LIF to the culture medium was found to be beneficial for bovine embryonic development based on cellular cryotolerance after vitrification. [ABSTRACT FROM AUTHOR]