Effect of feed supplementation, rearing system and genotype on the fat-soluble vitamins content of eggs: a review

Functional foods are foods that offer health benefits over and above their nutritional value. As eggs are a food of global importance, many authors believe that they are an ideal candidate for functional foods of the future, as it is possible to influence their chemical composition through production technology. Vitamins are one of the most important groups of micronutrients essential for human health, and eggs are recognised as an important source of vitamins in the diet, especially fat-soluble vitamins. The egg yolk contains large amounts of vitamins A, D, E and K. Eating two eggs a day covers 10% to 30% of a person's vitamin requirements. This paper reviews the results of a large number of researchers on the influence of various aspects of production technology on the content of fat-soluble vitamins in eggs. Most attention has been paid to the influence of vitamin supplements in feed for laying hens, but also to the influence of the rearing system and the genotype as well as the interaction between the vitamins.