The Ability of Hens to Maintain Calcium Deposition in the Egg Shell and Egg Yolk as the Hen Ages

Six strains of commercial egg-type hens (38 weeks of age) were fed a corn-soy diet containing 16.00% protein and 3.00% calcium for one year. Egg weight, shell weight, shell thickness, serum calcium, yolk weight and yolk calcium were determined at regular intervals throughout the experimental period. Egg weight increased and percent shell, shell thickness and percent yolk calcium decreased as the birds aged, however, shell weight remained fairly constant throughout the experiment. Since eggs get larger as the bird ages, this constant amount of calcium deposition may partially explain why shell quality declines as the bird ages.