Effect of embryonic 19-nortestosterone treatment and surgical bursectomy on plasma concentrations of reproductive hormones, on inhibin content in adrenals and gonads and on the histological appearance of the gonads in the young chicken

Abstract

Four-day-old chick embryos were hormonally treated with 19-nortestosterone in order to inhibit bursa development. At days 1, 4, 8, 15, 22, 29, and 36 of age, plasma, adrenals, and gonads from intact and hormonal treated chicks were collected. In embryonic nortestosterone treated males the appearance of a left ‘ ovotestis-like’ gonad was observed. The occurrence of this ovotestis-like left gonad in the 19-nortestosterone treated male is probably a secondary effect of the in ovo treatment since surgically bursectomised chicks did not show the testicular morphology and histological changes as observed in 19-nortestosterone treated chicks. Additionally, both male and female hormonally or surgically treated chicks showed relatively enlarged adrenal glands. Hormonal bursectomy affected organ inhibin contents and plasma inhibin, testosterone, and FSH levels in males. Male hormonal treated chicks showed lower levels of plasma inhibin ( p=0.0001), testosterone ( p=0.01), and FSH ( p=0.004), and a lower total testes inhibin content ( p=0.0003) compared to intact chicks. However, none of these were significantly different between female intact and hormonal treated chicks, again indicating that the observed hormonal changes in males are not the result of the disappearance of the bursa but of the hormonal 19-NT treatment. The total adrenal inhibin content as well as the adrenal inhibin concentration were significantly higher in hormonally treated chicks than in intact chicks ( p=0.0001), regardless of the sex.