Abstract
Bovine oocytes were collected from matured follicles. The number of cells in inner cell mass (ICM) and trophectoderm (TE) was measured by the differential fluorochrome staining technique for blastocysts fertilized in vitro. Blue ICM nuclei and pink TE nuclei were easily distinguished by propidium iodide and Hoechst 33342. The total number of cells increased with expansion and hatching of the blastocysts; 43 ± 18 (mean ± SD), 70 ± 27 and 112 ± 36 at the early, expanded and hatched stage of the blastocyst, respectively. The proportion of ICM cells was 14.2-14.5% at the early and expanded blastocyst stages and then decreased as blastocysts hatched (10.4%). Embryos ranked as excellent or good showed higher proportion of ICM cells to total cell numbers (17.6-17.8%) than those as fair or poor (12.8-14.3%) in the ealy stage of blastocysts. These results suggest that the differential fluorochrome staining technique is very useful for counting the ICM and TE cells of bovine blastocysts.
