The color of a duck's egg yolk is strictly dependent on their diet. Xanthophylls (pronounced zanthofils) are natural plant pigments and the more xanthophyll in the diet, the more orange will be the yolk.
The four most common poultry feed ingredients with high levels of xanthophylls are alfalfa meal, corn, algae and marigold petals. The only reason dried marigold petals are added to poultry feed is to make the yolks more orange in color. Green grasses have good levels of xanthophylls, too.
High levels of xanthophylls also make the skin more orange. In some parts of the United States, the demand is for a more yellowed skin broiler. In other parts, a more whitish colored skin is desirable. If you want a yellow skinned bird, feed predominantly corn. If you want a white skinned bird, feed predominantly wheat or barley.
The color of the yolk or skin has nothing to do with the freshness of the egg, nutrient content of the egg or meat, health of the bird or any type of cooking characteristic. It only indicates the feed eaten by the bird had higher levels of xanthophyll.
It is interesting that an orange billed duck, like a Pekin, that is in high egg production, will lose color in its bill and feet as the xanthophyll is transferred from its bill and feet into the yolk of the egg. Once they slow down in production and their consumption of xanthophyll is more than what is used in their eggs, their bill and feet become more orange again. Oftentimes you can use this as a way to determine which of your ducks are laying eggs. See our blog on this subject.
So what can you feed your ducks to get darker yolks? The easiest would be to allow your ducks access to green grass. This can be brought to them as lawn clippings or you can allow them on a pasture or lawn to graze. If you are in a colder climate with no fresh grass during the winter, you can give them alfalfa hay as a daily treat. If you have a choice of feeds at your local feed store, you can choose more yellow feeds (meaning a high level of corn) – making sure the feed is still completely balanced in its nutrients.
If you want to grow vegetables that are especially high in xanthophylls, try spinach, kale, cilantro, romaine lettuce, parsley, orange peppers or scallions. These will be good for you and your ducks!
In next week's blog, I will show you some of the projects we are doing here at Metzer Farms to prepare for another busy spring in 2011!