The concentration of vitamins is influenced by genetics, rate of egg production
and, as is the case with fatty acids, it varies with the composition of the hen’s diet
(Naber, 1993; Leeson & Caston, 2003). As the concentration of fat-soluble vitamins in
the feed increases, so does the content of vitamins in the egg yolk (Sirri & Barroeta,
2007).