Hen feathering

[2] Males of most chicken breeds distinguish from their females in having longer, sharp and more scalloped feathers in neck, hackle, saddle and wing bows.

It had been early established that hen-feathering is a trait controlled by a simple autosomic dominant gene, whose expression is limited to the male sex.

[3] [4][5] The genetic symbol proposed by F. B. Hutt in 1958 to designate this autosomic dominant gene was Hf (after "hen feathering")[6] which was accepted by other geneticists.

[8] This happens because hen-feathering requires a masculine hormone and in some cases first adult plumage is completed before testicles work normally.

[6][8][9] These variations in the expression of the character, even within the same individual, defies common sense and may confuse non-advised breeders who might expect a better mating behaviour in normal male-feathering cocks than in those of the hen-feathering type.

Some Sebright breeders consider hen-feathering to have adverse effect on the fertility of the male and may use cocks that do not carry the trait for breeding purposes, despite their automatic disqualification in shows.

In normal hf/hf individuals rates of estrogen formation are undetectable or low in all control tissues other than ovary.