Fig. 1

The eggshell ultrastructure in young (a; 42 wk. of age) and aged hen groups (b; 72 wk. of age; scanning electron microscope images, magnification, 200×). The ultrastructural characteristics (c&d) of eggshell in young and aged hen groups. MW, mammillary width; MT, mammillary layer thickness; ET, effective layer thickness; TT, total thickness. Data are the mean of 8 replicates with 24 eggs each. Asterisk represents a significant difference (P < 0.05) between groups