In cattle, small oocytes (group VII), included in small follicles, grow with follicular development, and the size and developmental competence of oocytes increase (groups I and II) (Nagano, Acquisition of developmental competence and in vitro growth culture of bovine oocytes, pp. 195-201). Subsequently, only one follicle is selected to develop to a dominant follicle and ovulates, but the other follicles start to degenerate. During the degeneration process, an accumulation of lipid droplets and undulation of the nuclear membrane of germinal vesicle start, and the developmental competence of oocytes also increases (pseudomaturation-like change in group III). However, too many pseudomaturation-like changes impair the developmental competence of oocytes (groups V and VI). If oocytes start to degenerate before pseudomaturation-like changes, the oocytes may become group IV.