KINETICS OF FIRST POLAR BODY EXTRUSION AND THE EFFECT OF TIME OF STRIPPING OF THE CUMULUS AND TIME OF INSEMINATION ON DEVELOPMENTAL COMPETENCE OF BOVINE OOCYTES

Kinetics of extrusion of the first polar body was examined as well as the effect of the time of stripping of the cumulus cells on this kinetics. In addition, the effects of time of stripping and time of insemination on developmental competence of the oocytes, as evaluated by the percentage of morulae and blastocysts, were studied. Polar body extrusion occurred in 80% of the oocytes between 12 and 18 h after the onset of maturation. The remainder of the oocytes did not extrude a polar body at all. Stripping of the cumulus at 12 h after the onset of maturation delayed polar body extrusion significantly by about 1 h. No significant differences were found in the percentage of oocytes that could be fertilized, and the percentage of oocytes that cleaved and developed to the morula and blastocyst stages, between oocytes that were stripped free of cumulus and inseminated at either 16 or 20 h after onset maturation. Oocytes that had extruded a polar body at either 16 or 20 h after onset maturation showed significantly higher percentages of cleavage and development than oocytes that had not extruded a polar body at those time points. However, the percentage of oocytes that could be fertilized was not affected.