EFFECT OF TIMING ON IN VITRO GROWTH AND PARTHENOGENETIC DEVELOPMENT OF PORCINE OOCYTE DERIVED FROM EARLY ANTRAL FOLLICLE (1-1.5MM)

Abstract

In large mammals, the number of eligible oocytes for maturation is limited. Almost all growing oocytes are eliminated after two recruitments before reaching their final size in nature. Therefore, the IVG system was established to supply essential factors, for instance, medium, supplements, and optimal environment for the growing oocytes to proliferate and achieve maturity and developmental competence. Among that, timing is crucial to the nuclear cytoplasmic synchronisation inside the oocytes. A suitable culture period would produce a high rate of fully grown oocytes, enhancing developmental competence and reducing aging and lethal stress. Thus, this study was constructed to determine the optimal duration of IVG for oocytes derived from early antral follicles (1-1.5 mm). Oocyte-cumulus cell complexes (COCs) obtained from early antral follicles were cultured in basic IVG medium three separate times: 3, 4, and 5 days before entering IVM and parthenogenesis IVD. The study resulted that the oocytes from 3, 4, and 5 days culture archived 101.6μm, 103.1μm and 111.0μm in measures after IVG, as well as showed the rate of clear expansion in cumulus layers (expanded from the outermost layer to all layers) after IVM was 6%, 20% and 24%, correspondingly. The results indicated that oocytes cultured for at least 5 days could provide an appropriate enhancement in cytoplasmic preparation as well as support for cumulus expansion during IVM. However, the percentage of fragmentation and denudation during IVG and IVM were demonstrated to be tremendously high, causing failure to assess meiotic morphology as well as support IVD. Yet oocyte developmental competence was also unevaluated, which suggested that the system requires cooperation with supplements as antioxidants and further anti-stress strategies.