Reproductive Development and Response of White Leghorn Pullets Subjected to Increasing Day-Lengths at Different Ages

REPRODUCTIVE responses of birds to increasing and decreasing photoperiods has been the subject of many studies. However, few reports have dealt with reproductive responses to increasing photoperiod changes at various ages. Change in length of the photoperiod had a greater effect on rate of sexual development and egg production than a constant photoperiod (Morris and Fox, 1958; King, 1958; Lert et al., 1960). Increasing light during the rearing period resulted in early sexual maturity, whereas, decreasing day-lengths retarded sexual development (King, 1961; Shutze et al., 1961; Shutze et al., 1961, 1963; Lowe and Heywang, 1964). Pullets reared on decreasing or short day-lengths, then subjected to increasing day-lengths, responded to the light stimulus with increased production and increased egg size (Morris and Fox, 1958; Shutze et al., 1963; Lowe and Heywang, 1964). Preconditioning of pullets by a reduction in photoperiod initiated prior to 14 weeks of age, resulted in increased egg…