Effects of Varying Daylengths on Laying Hen Production Rates and Annual Eggs

FOR several decades there has been a continued interest in the effects of photoperiodism on the domestic fowl. The general aspects of this phenomenon have been described in several recent reviews (e.g., Biellier and Ostmann, 1960). Current interest has focused on the effects of varying daylengths where sustained periodic changes are made in the daylength of laying hens. The origin of this interest may be traced to the early report of Whetham (1933) where the basic idea was presented that the response to light from laying hens was from a trend of change in daylength rather than from a quantitative photoperiod length. In addition to the benefits that may be derived from a program of increasing daylength during the laying period, benefits are also reported in subsequent egg production from hens subjected to programs of decreasing or restricted daylengths during the rearing period. It is clearly important to understand the…