rearing and laying periods. Poultry Sci. 40: 345-354. Pleiotrophic Effects of the Sex-Linked Delayed Feathering Gene, Kn, in the Chicken1

ABSTRACT In several series of comparative measurement studies the effect that the sex-linked delay feathering (K") gene had on comb and uropygial gland development was measured in chickens from two to 60 weeks of age. The gene's effect on heart, adrenal gland and reproductive organ weights were also determined. The comb and uropygial gland size differences were very dramatic throughout the whole age range. Combs of mutant birds were greatly reduced in size while the uropygial glands were greatly hypertrophied. Heart and adrenal gland weights were also significantly increased in the mutant birds. Gonad weights however showed no difference. Responsiveness of mutant chick's combs to injections of testosterone propionate was also tested and shown to have a response similar to that of non-mutant chicks. POULTRY SCIENCE 54: 208-216, 1975 THE most dominant of the three alleles at the sex-linked K locus, delayed feath-ering (Kn), is a gene whose action as it affects feather growth is quite extreme (Somes, 1969). Birds possessing this gene were nearly naked during juvenile life and in some cases females remained nearly naked well into adult life. As previously reported (Somes, 1969), the K " gene also appeared to affect organs other than the plumage of birds possessing it. This paper reports the results of several series of comparative measurement studies designed to determine the affect of this gene on comb and uropygial gland (oil or preen gland) development as well as its effect on heart, adrenal gland and reproductive organ weights. The responsiveness of the combs of mutant chicks to injections of testosterone propionate are also reported. It is suggested that the primary action of this gene may involve the gonadotrophic and gonadial hor-monal systems and that the difference