The main objective of the lighting program is to control sexual development. Sexual development can occur from an age of 11-12 weeks onwards. Sexual development is stimulated by an increase in light intensity and/or light duration. In broiler breeders, we want to delay the sexual development of the birds until the moment the birds are physically mature enough to react , we have to prevent any increase in light duration or light intensity from 11-12 weeks until we consider the birds developed enough to start production.