As feathers consist of dead cells and are consequently not fed by the metabolism, they absorb the colour when they are formed. On average, the plumage is changed once a year. However not in one go. The moulting of the old feathers is stimulated by the formation of new ones and this is a gradual process so that the bird keeps a full plumage. When adding Can-Tax to the food canthaxanthin is transported to the place where the feather is growing and it is given the more intense red colour. Betaapo8 carotenal ensures even better absorption of canthaxanthin.The feather formed retains its colour until the formation of a new feather.