In poultry standards, solid white is coloration of plumage in chickens (Gallus gallus domesticus) characterized by a uniform pure white color across all feathers, which is not generally associated with depigmentation in any other part of the body. Color is an important feature of most living organisms. In the wild, color has great significance affecting the survival and reproductive success of the species. The environmental constraints which lead to the specific colors of birds and animals are very strong and individuals of novel colors tend not to survive. Under domestication, mankind has transformed all the species involved which have thus been freed from environmental pressures to a large extent. Early color variants were mostly selected for utility reasons or religious practices. In more recent centuries color varieties have been created purely for ornament and pleasure, fashion playing a surprisingly large part in their development. A bewildering array of colors and patterns can now be found in the domestic fowl. In the last decades white plumage color has become essential for the efficient processing of broilers and most types of meat-type poultry. Slaughterhouses and meat processing plants require poultry with a white or very light undercolor to produce carcasses without the typical "hair", which colored chickens have, that necessitates singeing after plucking. There are several chicken breeds having solid white as the most typical plumage color, such as Leghorn, Dorking, Bresse Gauloise, Polish, Wyandotte and others. And there are many other breeds better known by their colored varieties, which also have a solid white variety, such as Plymouth Rock, Orpington, Rhode Island Red, Jersey Giant and others.
Description Chicks down color of solid white chicken breeds can vary from a light creamy white, through different yellow shades, to a toasted orange. In adult phase, the entire surface of the plumage is pure white due to the absence of melanin pigmentation in all parts of the feathers. The absence of melanin in the plumage of solid white chicken breeds does not affect other body structures, except in the case of the albinos, which are easily recognized by their pink eye color.
History Most chicken plumage color genetic factors were manipulated during domestication by selection and crossings, which led to the modern chicken breeds, but there are no historical records of when or where the first chicken breeds with solid white plumage arose. In the creation of new white breeds, white color have been sometimes introduced from breeds of solid white plumage. Rhode Island White arose from the work of J. Alonzo Jocoy of Peacedale, Rhode Island, which began in 1888. Developed through crosses of Partridge Cochins, White Wyandottes, and the rose comb type of White Leghorn, it was solidified as a breed by 1903. And it was first accepted into the American Poultry Association's Standard of Perfection in 1922. Moderately popular up until the 1960s, it is now a relatively rare fowl. On the other hand, there is not a unique genetic mutation for solid white plumage color. There are two very well known autosomal major mutations leading to solid white plumage color, but also a number of complementary mutations properly combined may reduce or restrict pigment with a sufficient intensity to produce a final solid white plumage color, even in the absence of the major mutations for white. Most varieties of solid white plumage chickens belong to some of the first two major mutations leading to solid white plumage color. These are commonly regarded as "dominant white" and "recessive white" according to the major mutation involved. The term "dominant white" has also been applied in genetic literature to a mutation producing white coat color in horses. Four different recessive albino or albino-like mutations which also produce white plumage color in the chicken were also reported in literature, but those are not typical of any breed of chicken, and may be associated to a reduced perinatal viability or a deficient vision.
Dominant white Dominant white was one of the first traits in aviculture which proved to be inherited according to the Mendelian laws, when in 1902 Bateson found that the cross of White Leghorns x Indian Games (or its reciprocal) gives F1 chicks with a white or a black spotted ashy white down. And that the F2 gives light and dark chicks in the 3:1 Mendelian proportion, which was confirmed by Hurst in 1905, Bateson and Punnet in 1906 and many others. The symbol I (inhibitor of black) to identify this mutation was introduced by Hadley in 1913. Although homozygotes I/I have always a solid white plumage color, heterozygous I/i+ chicks are generally black spotted, while the presence of black or partially black feathers on a whitish adult plumage is very common.
Recessive white Solid white varieties of Dorkings, Plymouth Rocks, Wyandottes, Minorcas, Orpingtons and other breeds are regarded as recessive whites because their white is completely recessive to any other color. Both kinds of white plumage: "dominant white" and "recessive white" are phenotypically identical in adult phase, and can only be distinguished from each other by means of a progeny test. In 1906 and 1908 Bateson and Punnet demonstrated that White Dorkings are homozygous for an autosomal recessive mutation which prevents appearance of color. They assigned to this mutation the symbol c, as being recessive from the normal allele (C+, chromogen) which allows normal plumage color development. This same kind of white plumage color was found by Bateson and Punnet in Rose Comb Bantam and in White Wyandotte. It was also found in White Cochin by Davenport in 1906, in White Langshan by Goodale in 1910, in White Plymouth Rock by Hadley in 1914, and in other breeds. "Recessive white" chickens may be potentially black barred or of some other color pattern, but does not reveal this, unless they are submitted to a progeny test. White Plymouth Rock chickens carry a considerable mixture of genes taken from other breeds different from the original Barred Plymouth Rock from which the white variety originates.
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