Biological methods of diagnosing equine pregnancy II—The capon test

Abstract

From a series of experiments on Brown Leghorn fowls Juhn and Gustavson (1930) suggested that the production of the red pigment in the breast feathers of the castrated male of this breed might be used as an indicator of the female hormone (œstrin). They were able to demonstrate the feminizing effect on the breast feathers of the capon within 48 hours of the injection of a single does of œstrin of the order of 600 rat units. This suggested the possibility of extending the use of the fowl test for œstrin, and of ascertaining whether or not the amount of this hormone in the urine of the pregnant of urine, a diagnosis of pregnancy could be obtained as early as 48 hours after injection. If this could be done the method would be of considerable practical value since the mouse test requires a period of five days from the initial injection before a result can be obtained. With this object a small series of tests have been carried out, and while it will be impossible for some months to verify or disprove the diagnosis from actual facts, they have been controlled and compared as regards results, sensitivity and uniformity with mouse tests on the same sample, the latter, up to the present having given over 99% correct diagnosis. Since the method may prove to be of practical import, the details of the experimental technique will be given at considerable length.