Abstract
Previous studies have shown that pigeons treated with estrogenic substances show a decided rise in blood calcium and a replacement of the marrow cavity by newly-formed endosteal bone. 1 It seemed of interest, therefore, to study the effect of estrogen on the bones and on the blood calcium of the domestic fowl. While our experiments were in progress, Zondek reported that estrogens increase bone calcification and raise the blood calcium level of chicks of both sexes. 2 These changes were associated with dwarfism.
Our material consisted of fully-grown and sexually-mature cocks. We used normal and Creeper cocks, the latter belonging to a breed characterized by chondrodystrophy-like disproportionate dwarfism. Except for one cock, which was 9 months of age, the animals were about 6 to 7 months old when the injections were begun. The body weight of the animals ranged from 870 g to 1620 g at the beginning of the experiment. Nine Creeper and 6 normal cocks were treated with daily injections of estradiol benzoate ‡; 5 Creeper and 5 normal cocks served for controls. In addition, similar tests were made with 2 capons (one normal, one Creeper), and 2 capons were used for control. The hormone injections were continued for various periods, as little as 3 weeks in some cocks, and up to over 4 months in others. The daily dose of estrogen varied between 1,700 and 30,000 I. U. With one exception, the cocks made normal gains in body weight during the experimental period.
At the beginning of the experiment the cocks still had rather small combs and wattles. During the course of the injections they decreased in size and assumed the typical capon-like appearance. The cock which was 9 months old when the injections were started, though he responded to the treatment in very typical fashion, still had a large, though somewhat mealy-looking comb after 3 weeks when the experiment was concluded.
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