The Effect of Photoperiodism and Rearing Period Feed Restriction on the Performance of Five Leghorn Strains

PHOTOPERIODISM and restricted feeding during the rearing period have been subjects of considerable study during recent years. This investigation was undertaken to estimate the separate and combined effects of some forms of these treatments on the design of comparative egg production tests when applied to commercial genotypes reared in windowless houses under confinement conditions. The experimental procedures used by different workers in the study of photoperiodism have varied widely and results tend to be somewhat contradictory. Biellier and Ostmann (1960), and more recently, Smith and Noles (1963), Davis et al. (1964) and Lillie and Denton (1965) have reviewed the literature on the effects of different photoperiods on the performance of egg production stock. A number of reports indicate that performance was improved for some traits when an increasing laying period day-length is coupled with either a constant 6- to 8-hour rearing period day-length or a rearing period with a day-length . . .