Delayed-feathering in chickens is a genetically determined delay in the first weeks of feather growing, which occurs normally among the chicks of many chicken breeds and no longer manifests itself once the chicken completes adult plumage.
The difference between fast normal feather development and delayed-feathering can be recognized in one-day-old chicks but is always more evident in 10- to 12-day-old chicks.
Female chicks have a slightly faster feathering than males. Barely seen in breeds with fast normal-feathering, this characteristic is better observed in breeds with delayed feathering, like Barred Plymouth Rock.[1]
Natal down color is not related to feathering speed, but in chickens of full-black adult plumage, chicks normally have shorter natal down than those from breeds of any other plumage color pattern [2] this shortening being more obvious in the head and back.
Feathering growth in the first weeks of life is genetically controlled by a few autosomal genes and a sex-linked gene.[1]
Most of the phenotypical variation among breeds can be explained by the sex-linked gene K. Autosomal genes retarding feathering growth are not typical in any particular breed. Because those genes are recessive, they need to be in homozygosity to manifest themselves, but as poultry farmers dislike bad-fledged birds, autosomal genes only subsist in very low frequencies.
Contrarily, sex-linked delayed-feathering is very frequent, particularly in meat-type breeds like Brahma, Cornish, Cochin, Rhode Island Red, Wyandotte, Plymouth Rock and Orpington.
Sex-linked genetic variation has proven to be very useful for the sex identification of one-day-old chicks in commercial hybrids.