Eggshell quality is a primary concern to the egg
producer because a cracked or broken eggshell downgrades
the egg and enhances the cost of producing
eggs. Eggshell problems are typical in aged laying hens
(Nys, 2001); numerous nutritional approaches have
been investigated to improve aged laying hen eggshell
quality. Manganese (i.e., Mn) is an important trace element
for layer nutrition.