Poultry farming is one of the most important livestock sectors in Spain, where about 210 eggs are consumed per person per year, a fact that reflects the great social importance of this food. The consumer is more and more aware of the quality and food safety of the products. The quality of the egg is determined by the control of its internal quality and by the absence of external defects on the shell. The alterations of the shell will depend on several factors: age of the hen, handling and situations of stress, nutrition, pathologies. These factors are going to have an influence on the external appearance of the egg and on its food security, which, in short, can mean its withdrawal from the consumption chain. This article makes a review of the influence of the productive phase of the hen in the incidence of presentation of alterations in the shell of the eggs, which will cause a decline in their economic value.

Keywords: Ca metabolism, stress in hens, cracked egg.