In Vitro Growth of Oocytes from Domestic Species

A huge number o f sma l l oocy tes a re contained in the ovaries of the pig and cow. A small number of them grow from the minimal size of 30 μm in diameter to the final size of 120–125 μm, then mature, and are ovulated. A large number of the remaining oocytes do not enter the growth phase or degenerate in the ovary. Oocyte growth takes a long time and is coordinated with surrounding follicle cells. During the growth phase, oocytes are required to be arrested at prophase I (GV stage), and to acquire the meiotic competence to mature to metaphase II. IVG culture systems have been developed for domestic species, although they are still being improved. IVG culture systems for small oocytes are expected to provide a new source of oocytes for livestock production as well as a better understanding of the basic mechanisms of oogenesis/folliculogenesis in the ovary.