Changes in the Ovotestes Transformed by Exogenous Estrogen During Incubation in the Male chicken after Hatching.
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The gonads of male chicks exposed to large quantities of exogenous estrogen during incubation appear ovarylike at the time of hatching. The purpose of the present study was to clarify the changes that occurred in the gonads after hatching.On the fifth day of incubation, 0.64mg of estoradiol benzoate (EB) was administered to hatching eggs to assess: histological changes in the gonads and changes in blood testosterone levels of male chickens between hatching and 402 days after hatching; the characteristics of ejaculated semen in mature male chickens; and the morphology of the accessory reproductive organs of mature male chickens.Increased body weight did not differ between control and EB male chickens.However, from hatching to 60 days later, the gonads of the EB chickens weighed less and histological analysis of these showed that the number of spermatids in the maturation phase was markedly lower in some male chickens by 104 days old, but these differences between the groups were not significant at 402 days. Between 104 and 139 days after hatching, the blood testosterone level was lower than that of the controls, but this ceased to be significant beyond 154 days after hatching. However, the surface of the EB chickens' testes was rough and some cystic structures of varying sizes projected over the testes. Semen collection was attempted by the massage method at 300 days after hatching. Cloacal inversion was absent in all male chickens.The number of spermatozoa ejected was 27.2% that for the control. The ductus deferens was 57.7% narrower than that of the control, and left and right oviducts of varying sizes were observed.The results suggest that major gonadal changes caused by exposure to exogenous estrogen during incubation were reversed after hatching, and also that the male chickens possessed normal testicular functions, such as androgen secretion and spermatogenesis. However, since the morphological changes caused by estrogen exposure during the early stage of incubation persist in the gonads and the accessory reproductive organs do not develop normally although a sufficient amount of androgen is secreted, these findings suggest that the influences of exogenous estrogen on the differentiation of the reproductive organs remain in matured male chickens.
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