Skin and plumage changes in domestic birds. I. Skin changes]

This study presents modifications of the common integument and specific integumental structures developed during the domestication process of different poultry species. These modifications include dewlaps, variations of the comb, ear lobes, and wattles, size and form variations of the beak, exuberances of the cere and orbital skin, spur defects, loss of the uropygial gland, and crop dilatations. Most skin modifications were genetically manifested by exhibition poultry, and perpetuated by deliberate selective breeding. Several of the skin modifications described severely impair the normal, species-typical way of life of the animals concerned. The range of negative influences exerted by some of the fancy breed characteristics includes physical disabilities as well as disorders in food intake, reproduction, and social behaviour. Additionally, genetic defects and pathogenic predispositions can be found.