Abstract

The effect of 17α-oxyprogesterone-17-capronate on molting of 19 species of birds was investigated. Birds fall into two separate groups with regard to their response to the hormone. Some species molt after injection and others do not. The birds of the first group are those which breed the year round, and the second group have a restricted breeding season. The latter are mostly wild species. Bengalees and canaries, respectively, in our tests were representative of each group. Oxyprogesterone capronate does not accelerate the growth rate of feather regeneration in either type of bird, but, rather, it inhibits it in canaries. The hormone seems to stimulate the resting papillae to become active in the birds of the first group and it can induce molt of the feathers of tail, wing and body. In Bengalees molt begins about one week after injection regardless of the amount of the hormone. The duration of molting, and the numbers of castfeathers are proportional to the dose from 1.25 to 6.25 mg. There is no sexual difference in the molting response to the hormone. Gonadectomy does not induce molt nor does it make any difference in molting response by Bengalees to oxyprogesterone capronate. Complete thyroidectomy in Bengalees inhibits the molt-inducing action of oxyprogesterone capronate, but partly thyroidectomized birds respond by molting. The molt is also induced by the hormone in birds treated with thiourea, but in this case the molting is delayed and prolonged. Oxyprogesterone capronate does not cause any significant histological changes in the thyroid glands in Bengalees. Desoxycorticosterone acetate, estradiol benzoate and testosterone propionate do not evoke molt either in Bengalees or canaries. From the results obtained, it is postulated that in Bengalees, oxyprogesterone capronate can induce molt by either 1) enhancement of sensitivity of feather papillae to thyroid hormone which can induce molt alone, or 2) synergistic action between oxyprogesterone capronate and thyroid hormone, or possibly a combination of those two.

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