A comparative study on developmental capacity to blastocysts derived from 1-and 2(3)-cell bovine embryos after in...

The present study was conducted to compare the developmental capacity of 1-and 2(3)-cell embryos after 18 and 30 h of fertilization, and blastocyst cell number and in vitro survival after freezing and thawing of bovine blastocysts derived from the 1-and 2-cell embryos. Oocytes were matured and fertilized by conventional IVM/IVF methods. After 18 or 30 h of fertilization, 1-cell embryos (18 h-fertilization) or 1- and 2(3)-cell embryos (30 h-fertilization) were cultured for 8 or 10 d in synthetic oviduct fluid medium (SOFM) supplemented with 10% human serum (HS), minimum essential medium (MEM) essential or nonessential amino acids and glutamine. The separate culture of 1- and 2(3)-cell embryos after 30 h of fertilization showed higher (p < 0.01) cleavage, development to expanded and hatched blastocysts than culture of 1-cell embryos after 18 h of fertilization. Two-cell embryos of 30 h-fertilization group had higher developmental capacity to expanded and hatched blastocysts than 1-cell embryos at 18 or 30 h after insemination (Experiment I). However, there was no significant difference in the mean cell number of blastocysts derived from the culture of 1-cell and 2(3)-cell embryos, respectively (Experiment II). The in vitro survival or hatching after freezing and thawing of blastocysts was significantly affected by embryonic quality before freezing, but did not significantly differ with blastocysts derived from 1- and 2(3)-cell embryos after 18 or 30 h of fertilization. The results indicate that the culture of 2(3)-cell embryos after 30 h of fertilization is an effective method to produce more transferable embryos (blastocysts) in bovine IVM, IVF and IVC techniques.