The timing of first cleavage of different cloned and IVF embryos with oocytes recovered by ovum pickup

Abstract

AbstractThe goal of the study reported here was to determine the developmental potential of cloned embryos using two donor cells [fetal‐derived fibroblast cells (FFCs) and adult‐derived fibroblast cells (AFCs)] and in vitro fertilization (IVF) embryos with oocytes obtained by ovum pickup (OPU) and the relationship between timing of first cleavage and pregnancy or calving rate. Heifers were subjected to OPU once weekly. In total, 1558 oocytes were recovered from 2033 follicles, a mean of 7.8±0.4 oocytes per session per animal. Mean oocyte production was similar not in quantity but in quality (proportion of each oocyte grade) among groups [FFC‐nuclear transfer (NT), AFC‐NT and IVF groups]. These oocytes were then subjected to somatic cell nuclear transfer (SCNT) and IVF. Although reconstructed embryos initiated cleavage sooner when the donor cells were from FFCs versus AFCs, cleavage of embryos in the IVF group occurred 1 and 2 h earlier than that in the FFC‐NT group and the AFC‐NT group. However, in vitro development to blastocyst and the pregnancy rates at Day 90 of gestation were different between donor cell types; four cloned calves were obtained and survived for more 6 months. Although in terms of cleavage rates and blastocyst rates, there were no significant differences between IVF and FFC‐NT groups, for in vivo development, the efficiency of IVF was higher than that of SCNT. In conclusion, the timing of first cleavage, pregnancy and calving rate differs by the source of donor fibroblast cells, and shorter timing of first cleavage may imply a higher pregnancy or calving rate. The oocytes obtained by OPU can be used as recipients for SCNT.