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hi go ke ip S.kn developmental stages with a considerable degree of In birds as in mammals ovarian folliculogenesisprecision, conferring a distinct advantage over com-DOI: 10.1530/REP-07-0070parable follicle maturation studies in mammals. q 2007 Society for Reproduction and Fertilityrequires the coordinate actions of intra-ovarian and systemic factors. Upon interaction with cognateIntroduction The functional left ovary of the laying hen typically contains six to eight large yolk-filled follicles (designated F1–Fn) that have been recruited to a well ordered and rapidly growing preovulatory hierarchy and are destined to ovulate successively at intervals of 24–26 h. Following ovulation of the largest F1 follicle (w40 mm in diameter), the succeeding F2 follicle will advance t