Testicular Hormones and Sebright Plumage.

Abstract

There are recognizable in the fowl 3 intergrading types of plumage, usually designated as hen-feathering, cock-feathering, and capon-feathering. The capon type, which does not occur normally in nature is, in effect, an exaggeration of the male form. It appears following the complete removal of testes or ovaries. Hen-feathering occurs in the presence of an adequate amount of functional ovarian tissue (native or grafted) in any individual, so far as known, without regard to breed or sex. It may also be induced by the injection of certain hormones, such as thyroxin, and occurs normally in males of certain breeds, notably Sebrights. Attempts to interpret these phenomena have led to 2 not wholly concordant views. One group of investigators has postulated differences in testicular hormones, pointing out that the degree of cock-feathering varies in different races, but that in all races the male is less elaborately feathered than the corresponding capon. Others have questioned the differential effect of testicular hormones on plumage. Roxas found that exchange of testes between hen-feathered and cock-feathered males had no effect on the plumage of either. Gallagher, Domm and Koch have recently reported that purified testicular hormone, while having no effect on capons of cock-feathered strains, readily induces hen-feathering in Sebright capons. They interpret these findings as indicating merely somatic differences in response to the same hormone. Results following skin transplantation, while for the most part supporting this contention, afford some indication of racial differences in the hormones themselves. The question is obviously still open, and calls for a more nearly quantitative analysis. The following experiments only partially meet this need. Three 5 1/2-months-old cockerels of Sebright type, full brothers, and very similar in appearance, were used for a gonadectomy test. In A the testes were left undisturbed, in B both were removed, and in C one was removed.