EFFECTS OF ASPIRATION VACUUM AND NEEDLE DIAMETER ON CUMULUS OOCYTE COMPLEX MORPHOLOGY AND DEVELOPMENTAL CAPACITY OF BOVINE OOCYTES

The effects of aspiration vacuum and needle diameter on the morphology of the cumulus-oocyte-complex (COG) and developmental capacity of the oocyte after IVF was studied in 2 experiments using a disposable ovum pick-up needle guidance system whose construction permits its use in vitro. In Experiment 1, the relationship was determined between the as piration vacuum, expressed in millimetre of mercury, and the actual am ount of water aspirated by the system, expressed in millilitre per min ute. In Experiment 2, five different levels of aspiration vacuum for 3 different needle diameters (18g, 19g and 21g) were tested in slaughte rhouse ovaries. The cumulus-oocyte complexes (COCs) were divided into 3 categories: 1) oocytes with a compact cumulus, 2) oocytes with an ex panded cumulus and 3) naked oocytes. The results show that a change of needle diameter can triple the amount of fluid actually aspirated. Th e highest oocyte recovery rates are obtained when using the thickest n eedle (Is-g), regardless of the aspiration vacuum. On the average, for all needle types, more oocytes are recovered at the highest aspiratio n vacuum. For all needle diameters, the proportion of oocytes surround ed by a compact cumulus decreases progressively as the vacuum increase s. Regardless of the vacuum applied, thinner needles result in a highe r proportion of recovered COCs with a compact cumulus. At a high aspir ation vacuum, naked oocytes become predominant regardless of the needl e diameter. The prevalence of blastocysts, expressed in proportion to the recovered COCs, decreases as the aspiration vacuum increases, bein g especially noticeable between 70 and 130 mm Hg.