Ingredients with a high concentration in natural pigments are few among those commonly used in poultry nutrition, and such ingredients are sought after to produce all-natural eggs for specific markets.
Feeds for commercial layers are usually supplemented with synthetic pigments to ensure egg yolk has a desired and, even more importantly, consistent color; ranging from golden yellow to deep orange-red depending on local preferences. There is, however, a small but increasingly significant market, in which all-natural ingredients are all that are allowed to be used in layer feeds, and as such, synthetic pigments are excluded. For this market, for which egg yolk color is as important as any other market, two aspects that largely control egg pigmentation must be considered: type and concentration of pigments.
Pigments that impart a yellow or orange color to egg yolk belong to an oxycarotenoid group called xanthophylls. The most important xanthophylls for egg yolk coloration are zeaxanthin and lutein. The former is causing egg yolks to be more orange-red in color, while lutein imparts a more yellow hue. The balance between these two major xanthophylls is what determines final color in egg yolks. Equally important to this balance is the total xanthophyll concentration in feed. As a rule of thumb, to achieve a satisfactory saturation of color, the feed must contain at least 15-20 ppm total xanthophylls.
From among commonly available ingredients, maize is considered a good source of xanthophylls (20 ppm), followed by the less frequently encountered but very powerful maize gluten meal (275 ppm), and the infrequently used alfalfa meal (175 ppm). Maize and maize gluten meal are rich in zeaxanthin (4 ppm in whole maize), whereas alfalfa meal is rich in lutein (64 ppm). An unusual source of natural xanthophylls is marigold petal meal, which was added quite frequently in commercial feeds before the advent of synthetic pigments. The concentration of xanthophylls in Marigold petal meal is 7000 ppm. More recently, the use of certain algae as a source of natural pigments has been investigated as it was found they can contain up to 2000 ppm xanthophylls.
Another consideration in the effort to provide layers with feeds rich in natural pigments is that xanthophylls are quite unstable compounds and as such they deteriorate quite easily during storage. As such, the addition of a strong (natural) antioxidant will help maintain the potency of natural pigments for longer. In addition, avoiding excesses of vitamin A will help increase yolk color intensity as this vitamin has been shown to antagonize xanthophylls in their role as pigments. Finally, ensuring pullets enter egg production with highly colored shanks (by providing high levels of xanthophylls in the grower feed) will maintain a deeper egg yolk color for longer as hens draw from their body pigment reserves (shanks and skin) to supplement what they receive from their feed on a daily basis.
In conclusion, layer feeds based on maize and supplemented with alfalfa meal or maize gluten meal can satisfy the need for all-natural eggs with sufficient yolk coloration. Deeper color can be achieved by using marigold petals and algae, but the xanthophyll composition of these ingredients can be very variable as it is product specific.