How diet influences the quality of eggs

Abstract

Farmers are mainly interested by egg weight and eggshell strength. Egg weight is linked with several factors : breeding lines, hen’s age and nutrient supply to pullets and hens. Hen’s weight at the laying point, energy and protein densities of the diets, amino acid (primarily methionine) and fatty acids (linoleic and oleic) contents impact egg weight. Feed form and feeding system require future research to evaluate quantitatively their effect, keeping in mind that they are meaningful. Eggshell strength is determined by quantitative Ca supply and Ca particle size. Egg product companies are more interested in yolk and albumen contents. The latter are mainly linked with the hen’s age. However marginal changes in proportion are observed through protein, amino acids and linoleic acid supplies. For criteria of consumers’ interest, a straight link is observed between the fatty acid contents of the diet and of the egg. It is therefore possible to optimize the egg nutritional value through feeding. Macromineral content is stable. However numerous microminerals (Iode, Selenium, Manganese) and fat-solubles vitamins (E, D3, A and K) contents could be modified by the diets. Yolk colour depends on feed supply since hens cannot synthesize carotenoids. However, coloration efficiency is variable depending on the supplied xanthophylls.