The effect of manganese deficiency upon the ultrastructure of the eggshell.

Manganese deficiency in the laying hen results in decreased egg production and eggshell thickness. Eggshells from deficient hens show specific changes in appearance characterized by translucent areas. Examination of these translucent areas with the scanning electron microscope revealed changes in the ultrastructure of the shell. The most prominent feature was large irregular mammillary knobs probably due to the fusion of several mammillary cores during the early phases of eggshell formation. Chemical analysis of the organic matrix of the eggshell showed a decrease in hexosamine and hexuronic acid content consistent with the known role of manganese in polysaccharide synthesis. Studies on the characteristics of the polysaccharide chains isolated from normal eggshells suggested that these polysaccharides were considerably different from those isolated from cartilage proteoglycans.