The effect of orally administered synthetic oestrogen (Hexoestrol) on the male fowl

Abstract

In three experiments, involving a total of 141 male fowls, the effect of orally administered hexoestrol on cockerels of different ages and breeds was observed, and the results were compared with those from untreated birds and capons. The results obtained support the hypothesis of a twofold action of oestrogen, viz. its action as a stimulator during an initial period and as a depressor of the anterior pituitary gland after a certain threshold level has been reached. The sensitivity to oestrogen increased with age, varied according to different breeds, e.g. White Leghorns gave a smaller response than Australorps, and varied according to tissue, e.g. it was higher for the testes than for the comb and epidermis. It was observed that the size of the testes in three-month-old cockerels varied greatly and that the amount of abdominal fat was not closely and reliably correlated with the total body fat. Oestrogen treatment improved the appearance of the carcass. Deposition of abdominal fat was increased only for Australorps and mature birds. Capons were superior in body-fat production to the oestrogen-treated birds. Fat from birds treated with hexoestrol (up to 25 mg. daily for three weeks) did not produce oestrogenic effects when injected into mice. The observations did not support the hypothesis of Wheeler and Hoffman (1948) that oestrogen treatment increases the occurrence of prolapse and "pickout".