Studies with Decreasing Lighting Regimes for Early-Season Replacement Pullets under Subtropical Conditions

THE increasing day length during the growth period of winter-hatched pullets seems to stimulate their sexual development, resulting in smaller-bodied layers which produce smaller eggs and which do not appear to have the capacity to lay at a high rate over an extended period. Consequently, different systems of quantitative or qualitative feed restrictions and various lighting programs have been designed in order to delay sexual maturity and prevent pullets from starting to lay at too early an age. A voluminous literature, reviewed extensively by Biellier and Ostmann (1960), has accumulated concerning the influence of light on the regulation of ovarian activity in birds. Morris and Fox (1958a, 1960) have proposed that the rate of maturation of pullets is directly proportional to the rate of change in daylength experienced by them from hatching to maturity, whereas King (1961) related sexual maturity to hours of constant light received by the pullets. These…