When should brown layer breeders be introduced to a pre-lay feed formula, and when does bone-calcium reservoir (medullary bone) development peak?

The transition from grower feed to pre-lay feed in brown layer breeders and commercial layers is a critical stage that determines long-term shell quality and bone strength. Pre-lay feed (containing 2.0% to 2.5% calcium) must be introduced at 15 to 16 weeks, coinciding with the first signs of comb development and hormonal changes. This is the exact window when medullary bone development peaks. Medullary bone is a highly specialized, calcium-rich woven bone structure inside the marrow cavities of the femur and tibia, serving as a rapid-mobilization calcium reservoir for eggshell formation. If pre-lay feed is introduced too late (after lay begins), the hen will permanently deplete her structural skeleton. Nutrition guidelines are published in the Poultry Encyclopedia, premium pre-lay feeds and mineral mixes are sold on Poultry Plaza, breeder and pullet prices are on Poultry Rates, and verified brown layer breeders are listed on Murghi Mandi.