Abstract The influence of hen age on some egg characteristics was studied. Two commercial breeds of brown hens, namely Warren and Hy-Line, were considered at seven different ages. The variables analyzed were the weights of yolk and thick and thin albumen, pH, and the concentrations of glucose, uridine, and uric and pyroglutamic acids of separated yolk and albumen. Albumen and yolk average weights and the proportion of yolk in the edible part of egg increased with hen age, whereas the average ratio of thick to thin albumen was not influenced by the progress of the laying cycle. Glucose, uridine, and uric acid were also not influenced by hen age. Pyroglutamic acid, which is detectable in yolk and not in the albumen of a fresh egg, showed a characteristic trend in yolk. Its concentration dramatically increased in the middle of the laying cycle and then decreased to values close to those observed in eggs of the young layers
