Chicken in Mexico has noticeably yellow skin compared to chicken in the United States and Canada This distinct yellow color is due to a combination of factors involving genetics, diet, and selective breeding
Genetics Play a Role
Research has found that the yellow skin of modern chickens likely originated from the grey junglefowl, a wild relative of chickens, rather than the red junglefowl that is considered the sole ancestor of domesticated chickens A genetic mutation in the grey junglefowl allowed for increased deposition of yellow carotenoids in the skin This mutation was then passed on to domesticated chickens through breeding.
Diet Influences Color
While genetics set the potential for yellow pigmentation, diet determines how yellow the chicken skin ultimately becomes. The carotenoids that cause the yellow color are organic pigments found in plants. Chickens obtain carotenoids from their feed. The more yellow carotenoids present in the feed, the yellower the chicken’s skin will be.
Commercial poultry feed in Mexico contains higher levels of yellow carotenoids like marigold petal meal compared to typical feed in the U.S. and Canada. This results in chickens developing much yellower skin. Free-range chickens that forage on carotenoid-rich plants also tend to have very yellow skin.
Humans Selectively Bred for Yellow
In addition to naturally occurring genetic variation, humans have selectively bred chickens to intensify the yellow skin trait. Chickens with yellow skin have been preferred by many cultures throughout history. Scientists believe this is an aesthetic preference related to perceptions of health, fertility, and distinct appearance.
Through selective breeding focused on yellow skin over many generations, the domestic chicken has become genetically predisposed to producing yellow pigmentation when fed a carotenoid-rich diet. Farmers and breeders in Mexico have emphasized this trait more than others.
The Result is Distinctly Yellow Chicken
The combination of original junglefowl mutations, a carotenoid-rich diet, and selective breeding has resulted in chickens with markedly yellow skin being the norm in Mexico. The preference for yellow chicken has shaped poultry production to prioritize this trait. While genetics limit the potential yellowness, feeding high carotenoid diets allows modern Mexican chickens to fully express this prized yellow skin.
Figure Adapted from [2],[17].
Panel A depicts a map of South Asia onto which the ranges of four species of junglefowl are drawn. Panel B depicts a European domestic chicken with yellow legs. Red, grey, blue, and green regions represent the respective ranges of red, grey, Ceylon, and green junglefowls. s of these birds are presented in panels C through F respectively, within colored borders that correspond to the colors on the map. (Photo: Figures 1B: Björn Jacobsson; 1C: Erik Bongcam-Rudloff; 1D: John Corder, World Pheasant Association; 1E: Jean Howman, World Pheasant Association; 1F: Kenneth W Fink, World Pheasant Association).
The majority of chickens used for commercial egg and meat production in the Western world are homozygous for the yellow skin allele. In live birds, the phenotype is most easily recognized by the presence of yellow legs. The expression of yellow skin is influenced by the amount of carotenoids, primarily xanthophylls, in the feed [1]. More carotenoids produce a more intense yellow color. There is a strong consumer preference for the yellow skin phenotype in certain geographic markets such as USA, Mexico, and China where synthetic pigment may be added to enhance the yellow color [8],[9]. Carotenoids also play a crucial role for feather or skin pigmentation in some wild birds, a well-known example of which is the flamingos pink feathers. Carotenoid-based ornaments (skin or feathers) in wild birds are considered to be an honest signal of an individuals nutritional status or health, reflecting its foraging efficiency or immune status and are therefore implied to affect sexual attractiveness [10]–[12]. A better understanding of the molecular mechanisms regulating the distribution of carotenoid pigmentation is therefore of considerable interest for evolutionary genetics.
Jonas Eriksson1Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, SwedenFind articles by
Received 2007 Oct 8; Accepted 2008 Jan 23; Collection date 2008 Feb. Eriksson et al.
This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
Yellow skin is an abundant phenotype among domestic chickens and is caused by a recessive allele (W*Y) that allows deposition of yellow carotenoids in the skin. Here we show that yellow skin is caused by one or more cis-acting and tissue-specific regulatory mutation(s) that inhibit expression of BCDO2 (beta-carotene dioxygenase 2) in skin. Our data imply that carotenoids are taken up from the circulation in both genotypes but are degraded by BCDO2 in skin from animals carrying the white skin allele (W*W). Surprisingly, our results demonstrate that yellow skin does not originate from the red junglefowl (Gallus gallus), the presumed sole wild ancestor of the domestic chicken, but most likely from the closely related grey junglefowl (Gallus sonneratii). This is the first conclusive evidence for a hybrid origin of the domestic chicken, and it has important implications for our views of the domestication process.
Many bird species possess yellow skin and legs whereas other species have white or black skin color. Yellow or white skin is due to the presence or absence of carotenoids. The genetic basis underlying this diversity is unknown. Domestic chickens with yellow skin are homozygous for a recessive allele, and white skinned chickens carry the dominant allele. As a result, chickens represent an ideal model for analyzing genetic mechanism responsible for skin color variation. In this study we demonstrate that yellow skin is caused by regulatory mutation(s) that inhibit expression of the beta-carotene dioxygenase 2 (BCDO2) enzyme in skin, but not in other tissues. Because BCDO2 cleaves colorful carotenoids into colorless apocarotenoids, a reduction in expression of this gene produces yellow skin. This study also provides the first conclusive evidence of a hybrid origin of the domestic chicken. It has been generally assumed that the red junglefowl is the sole ancestor of the domestic chicken. A phylogenetic analysis, however, demonstrates that though the white skin allele originates from the red junglefowl, the yellow skin allele originates from a different species, most likely the grey junglefowl. This result significantly advances our understanding of chicken domestication.
The origin of the domestic chicken has been under debate for centuries [1]. Not only has the geographical center of the first (and possible additional) domestication event remained contentious [1]–[3], but because several closely related species of junglefowls exist in South Asia (Figure 1), the possibility that chickens originate from multiple wild ancestors has yet to be eliminated. On the basis of observed character differences and cross-breeding experiments, Darwin concluded that domestic chickens were derived solely from the red junglefowl [4], though this was later challenged by Hutt [1], who stated that as many as four different species of junglefowls may have contributed to chicken domestication. Molecular studies of mtDNA [5] and retroviral insertions [6] have supported Darwins view. A study that analyzed both repeat nuclear elements and mitochondrial sequences found evidence that grey and Ceylon junglefowls may hybridize with domestic chickens, but did not provide evidence that these two species have contributed to chicken domestication [7]. To date, no studies have compared gene sequences associated with a specific phenotype found in domestic chickens across numerous wild junglefowls and domestic breeds.
Why Are Chicks Born Yellow? #shorts #viral
FAQ
Why is chicken yellow in Spanish?
The characteristic yellow colour of the Coren Pollo de Coral free-range chicken comes from the daily intake of corn. The characteristic yellow colour of the Coren Pollo de Corral free-range chicken comes from the daily intake of corn. The chickens are bred in farms with at least 1 m2 of available space per bird.
Why is chicken different in Mexico?
Mexican chickens are often fed a diet that includes lots of marigold and calendula flowers, turning their skin a noticeable yellow
What causes chicken meat to be yellow?
Marigolds are added to poultry diets as a nutritional supplement because they improve meat quality and act as a natural pigment for enhancing the color of egg yolks. This pigment also colors the flesh, which is why you’ll sometimes see raw chicken flesh with a yellowish tint.