Genetics of the Black Skinned Chicken
The preferred color of chicken skin, as well as the color of cooked chicken, varies widely throughout the world.
Did you ever really stop to think about what color of skin your chickens have? Most of us are aware of white skin or yellow skin in chickens. If you raise Silkies or Ayam Cemanis, both of which are types of black skinned chicken, you are well aware of this lesser-known skin color, too. However, how many of us with just everyday backyard flocks stop to notice whether Flossie, Jelly Bean, or Henny Penny have yellow skin, white skin, or some genetically mixed color under all of those feathers?
It was not too many years ago that homemakers in both the United States and Europe had definite preferences for what color skin a dressed chicken should have. Butchers, poultry-shop owners, and farmers who raised birds for meat became very aware of their customers’ preferences and learned to cater to them. In the United States, especially the Midwest, yellow skin was preferred. In England, homemakers and cooks wanted white-skinned fowl. In fact, not just any white skin. There was a definite preference for white-skinned birds that had a slight pinkish cast or pigmentation to the skin. Why, I will never know, when they all turned brown when roasted.
In chickens with either white or yellow skin, white skin is genetically dominant to yellow skin. The absorption and utilization of the yellow pigment, xanthophyll, found in both green feeds and corn, plays a large role in how deeply colored the yellow skin becomes in birds with yellow skin and legs. In white-skinned birds, diets high in xanthophyll generally do not affect the color of the skin. Excess dietary xanthophyll in these birds is deposited in the fatty tissue, causing yellow fat but not yellow skin. In birds with blue, slate, black, or willow-green legs or shanks, the leg color is mainly caused by the pigment melanin, which is produced by the bird’s own body. This is a genetic trait and several factors, including “helper” or modification genes and which layer of skin the melanistic pigment is deposited into, determine the color of the legs of the given breed.
Much less known in North America are black skinned chicken, as well as those with black muscles, bones, and organs. This is a dominant genetic trait, known as fibromelanosis, in which the pigment melanin is distributed in the skin, connective tissue, muscles, organs, and bones, causing them all to be black or a very dark purplish-black. Probably the two best known black-skinned chicken breeds are Silkies and Ayam Cemanis. Silkies were bred in both China and Japan. They were introduced to Europe and the United States in the days of the sailing ships. They are a well-established and popular breed.
Much Newer to the Western Hemisphere is the Ayam Cemani. Originating from Central Java, this breed is known for its totally black feathers, jet black skin, comb, wattles, and legs. The inside of the mouth is solid black, as well as are the muscles, bones, and organs. It is one of the darkest fibromelanistic breeds in existence. Contrary to some myths, Ayam Cemanis lay a creamy white or light brown egg, and not black eggs. Their blood is also a deep red and not black.
While these fibromelanistic breeds (also known as breeds with hyperpigmentation) are somewhat rare in the Western world, they have been in existence and well-known for several thousand years in Asia, including China, Viet Nam, Japan, India, and many South Sea Islands. There are also a few breeds and landrace populations of these birds in Chile and Argentina. Sweden also has a national breed known as the Svart Hona, which is all black, inside and out. The Svart Hona reportedly has Ayam Cemani in its ancestry. In some regions, especially Asia and India, chickens with black skin, organs, bones, and muscles are very popular and are the birds of choice for not only food but also for their perceived medicinal qualities. Silkies were noted in Chinese medicinal writings over 700 years ago.
Fibromelanistic breeds, however, are known for producing black skin, meat, organs, and bones, which remain black, purplish-black, or greyish-black when cooked. These blackish colors of cooked chicken are revolting to many in the Western world yet are seen as delicacies in certain regions of China, India, and Southeast Asia.
Many black skinned chicken breeds produce meat that has significantly higher protein levels, as well as higher levels of carnosine, one of the building blocks of protein. Over the past two decades, laboratory research and study has increased significantly on the tissue structure and embryonic development of these breeds. By studying chicken feather and skin development during embryogenesis, scientists discover many factors that often translate into human health and medicine at later dates.
While the genetic trait for black skin is dominant, the depth of coloration is affected by individual modifying genes in the individual breeds. This is why some breeds, such as the Ayam Cemani, have all black skin, including combs and wattles, while others will show tinges of red in these areas, blue ear lobes, or have black flesh and bones with a grey or purple cast.
Just how many breeds or types of black-skinned chicken breeds are there in the world? According to a paper published by two researchers, H. Lukanov and A. Genchev, in the 2013 journal Agriculture, Science and Technology, at the Trakia University in Stara Zagora, Bulgaria, there were at least 25 breeds and landrace groups of these birds, most of which came from Southeast Asia. China had several well-known and well-distributed breeds within the nation. Other nations, including India, also had regional breeds of these melanistic, black-skinned chickens.
One very popular and pretty bird farmed commercially in China for its blue eggs, as well as black skin, meat, and bones, is the Dongxiang breed. In India, another breed of chicken with black skin, meat, and bones, the Kadaknath, is extremely popular. Hailing from the Indian state of Madhya Pradesh, the Kadaknath is in such demand that it was in danger of becoming extinct. The state government considers it a regional treasure and started a program which hired 500 families existing below the Indian government’s poverty line to raise commercial populations of the bird to meet the regional demand.
The color and hues of chicken skin, as well as coloration in the meat, organs, and bones, have wide diversity throughout the world. The extreme and fascinating genetic variances that these little creatures possess just add to the many reasons why most of us find them so irresistible. So, what color skin do your chickens have?
Originally published in the June/July 2019 issue of Backyard Poultry and regularly vetted for accuracy.