Abstract EGG production in poultry is a complex quantitative trait showing considerable variation over time within the production period of a hen. Several methods of expressing egg production and its component characters (age at first egg, broodiness, egg production during different periods of the total production period, etc.) which apparently contribute to the total variation in egg production have been investigated. It has been well established that heritability of egg production, as well as heritability of its component characters is low (King and Henderson, 1954; Jerome et al., 1956; Morris, 1956; Saeki, 1957; Oliver et al., 1957; Hicks, 1958; Bray et al., 1960; Carson et al., 1960; King, 1961; Wheat and Lush, 1961; Van Vleck et al., 1964; Acharya et al., 1969). However, one of the major weaknesses of conventional analyses of egg production data, as suggested by Tonkinson et al. (1969), is “the failure to recognize the entire curve by…