Removal of Cytoplasmic Lipid Enhances the Tolerance of Porcine Embryos to Chilling

The lipid content of porcine-cell stage embryos was reduced (delipated) through the use of micromanipulation to remove the lipid layer formed after centrifugation. Of 94 delipated embryos chilled to 4C for 1 h at the 1-cell or 2- to 4-cell stage, 60 (64%) cleaved in culture with development to the morula-blastocyst stage, whereas all of the control embryos lysed within 24 h. Significantly more embryos developed beyond the 8-cell stage when they were chilled at the 2- to 4-cell stage compared with chilling at the 1-cell stage (44%, 20 of 45 vs. 18%, 9 of 49). Fewer embryos developed after chilling if they were only partially rather than fully delipated. Developmental rates of partially delipated embryos to the 8-cell and blastocyst stages were 33 % (13 of 40) and 8 % (3 of 40), rates significantly (p < 0.001 and 0.05) lower than the rate for fully delipated embryos (73%, 38 of 52 and 27%, 14 of 52, respectively). The in vitro developmental competence of the unchilled fully delipated embryos wa