Why is a slow step-down lighting program during the rearing phase (0 to 17 weeks) essential to prevent premature sexual maturity in brown pullets?

Pullet rearing is a race against physiological clocks. If a pullet matures sexually too early (before 17 weeks), her skeletal frame and reproductive tract are underdeveloped. This leads to a high incidence of vent prolapse (blowouts), small egg sizes, and a rapid drop in peak lay persistency. To control the onset of sexual maturity, a strict "step-down" lighting program is utilized. In open or semi-open houses in Pakistan, pullets reared during seasons of increasing day-length (spring) are highly susceptible to early stimulation. By starting day-old chicks on 23 hours of light and gradually stepping it down by 1 to 2 hours weekly until reaching a constant 10 to 12 hours by 10 weeks, the pullet's brain (hypothalamus) does not receive any premature photostimulatory signals. This delay allows the bird to build a strong frame, deposit medullary bone, and achieve a uniform target weight of 1.4 kg before light stimulation is reintroduced at 17 weeks. Farmers can study photoperiod schedules in the Poultry Encyclopedia, buy automatic climate and lighting controllers on Poultry Plaza, monitor rate margins on Poultry Rates, and list healthy pullets on Murghi Mandi.