Why do brown pullets require a minimum target body weight of 1,400 grams before receiving the first light stimulation?

Photostimulation (increasing day-length from 9 to 14 hours) activates the pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which rapidly matures the ovaries. However, the timing of this stimulation must never be based on age alone. If brown layer pullets are photostimulated before they reach the critical threshold of 1,400 to 1,500 grams, their skeletal frame and muscular reproductive tract are not mature enough to support egg production. The hen will lay a high percentage of small, low-value "pullet eggs" (under 45 grams) for several weeks, and the narrow pelvic structure increases the risk of oviduct prolapse (blow-outs) and subsequent cannibalism. Furthermore, she will fail to build sufficient medullary bone reserves, leading to early-onset osteoporosis. Delaying light stimulation until the flock reaches 1,400g with 85% uniformity ensures a high, stable peak-lay curve. Farmers can find body weight charts in the Poultry Encyclopedia, buy premium developer feeds on Poultry Plaza, monitor daily rates on Poultry Rates, and trade pullets on Murghi Mandi.