A relation between experimental hyperthyroidism and barring in poultry.

Abstract

When the thyroid secretion of the domestic fowl is augmented by the addition of desiccated thyroid in the diet, or by the injection of thyroxin, changes in the moulting process and in the form, structure and color of new feathers occur, some of which have been described elsewhere. 1 Among these effects, one of the most notable is a modification of the form of certain feathers in the male that have a broad lacy border of naked barbs. The width of this border loses its normal uniformity, becoming narrower at some points than at others, owing to the unusual extension of barbules at these points on to the barbs. The contour of the central barbuled area thus presents a more or less regular series of scallops.

This structural change was first observed in Rhode Island Red males but its significance overlooked because of its relative irregularity. In Brown Leghorn males, however, the regularity of the marking in the hackles suggested a correlation with the pigment bars of barred breeds such as, for instance, the Barred Plymouth Rock. This surmise proved to be correct. When Barred Plymouth Rock males were fed thyroid, their new hackles displayed the same characteristic scalloping, and in this case the scallops corresponded closely with the pigment bars. When male Campines were given injections of thyroxin,² hackles, that followed white feathers that were plucked, contrasted sharply with the latter, both in color and structure. Not only was there a quantity of dark pigment, but it was laid down in a pattern in which bars could be readily recognized. And the scallopings characteristic of the feathers of thyroid-fed birds were associated with the pigment bars, as in Barred Plymouth Rocks.