When do brown layer flocks reach their physiological point of peak persistence (retaining egg production above 90%), and when does eggshell quality begin to decline?

Modern brown layer genetics are bred for high production persistence. After reaching peak production intensity (often up to 95-96% at 25 weeks of age), a well-managed flock should maintain peak persistence—retaining egg production above 90%—for up to 20 weeks, continuing until 45 weeks of age. After 45 weeks, production gradually declines by 0.5% to 1% weekly. Conversely, eggshell quality (thickness and strength) begins its most noticeable decline after 50 weeks of age. This occurs because egg size continues to increase with hen age, while the total amount of calcium carbonate the shell gland can secrete remains constant, resulting in thinner shells over a larger surface area. Uterine receptor sensitivity to vitamin D3 also degrades with age. Aging flock management is covered in the Poultry Encyclopedia, shell stabilizers and organic trace minerals are sold on Poultry Plaza, egg and bird rates are updated daily on Poultry Rates, and productive laying flocks are listed on Murghi Mandi.