“…Eggshell quality is influenced by internal and external factors including genotype, age, laying time, cage system, and balanced feeding with adequate Ca, P and mineral supplements (Ketta & Tůmová, 2016). Calcium supplementation is the key to eggshell quality, because each eggshell contains up to 3 g of Ca, so chicken feed must contain Ca in sufficient quantities and be used efficiently (Bartter et al, 2018;Rayan et al, 2022). The physical quality of the eggshell such as shell thickness, shell hardness index and shrinking the pores of the eggshell so as to protect the egg contents (Alig et al, 2023).…”