The pigmentation of chicken eggshells is the result of a complex interplay of genetic, metabolic, environmental and technological factors. Key pigments such as protoporfhyrin IX, biliverdin IXα and its zinc chelate are synthesised in the epithelial cells of the uterus and deposited in the calcified layers of the shell and cuticle. Genetic mechanisms include the expression of genes such as ALAS1, HO-1, ABCG2 and SLCO1B3, with retroviral insertion contributing to the appearance of blue eggshell pigmentation in certain breeds. Pigmentation is significantly influenced by nutrition (including micronutrients, vitamins and antioxidants), health status, ,stress, pharmacological agents (e.g. nicarbazin) and the age of the hen. These pigments play an important role in protecting the embryo from UV radiation, oxidative stress and mechanical different methods for measuring eggshell colour, including the CIE-Lab* colour system, spectrophotometry and high performance liquid chromatography (HPLC). Each method offers specific advantages depending on the intended application, ranging from routine industrial quality control to high-precision scientific analyses. A deeper understanding of pigmentation mechanisms supports the development of targeted breeding, nutritional and diagnostic strategies and helps to optimise poultry production and improve egg quality.
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