Body weight at point of lay and the ultrastructural properties of eggshells

Ultrastructural studies have demonstrated that the eggshell is comprised of morphological distinct calcified layers with the mammillary layer being the "foundation" of the eggshell. Studies have identified ultrastructural variations in the mammillary layer that can be used as indicators of eggshell quality (Roberts and Brackpool, 1995). Understanding the ultrastructure of eggshells has reinforced the view that the mechanical properties of the eggshell cannot be defined by a simple thickness measurement (Bain, 2005). Body weight at point of lay is a major factor influencing subsequent egg size, and this applies to both immature and more mature ages (Leeson and Summers 1987). Larger birds consume more feed while producing larger sized eggs with inferior eggshell quality (Leeson and Summers, 1987; Parkinson et al., 2007). The current study was conducted to investigate the relationship between body weight at point of lay and ultrastructural properties of the mammillary layer of the eggshell.