Gonadal development and growth of chickens and turkeys hatched from eggs injected with an aromatase inhibitor

It was the purpose of these experiments to describe gonadal development and posthatching growth of genetic female chickens and turkeys following irt ovo injection of the aromatase inhibitor Fadrazole (R) (CGS 16949A) prior to incubation. In ovo injection of Fadrazole (R) (CGS 16949A) resulted in the development of testes-like gonads in the majority of day-old genetic female chickens and turkey poults. Ninety-eight to 99% of these birds have masculine-type male genitalia at 1 d of age. Microscopic examination of the gonads of day-old genetic female chicks hatched from Fadrazole (R)-treated eggs showed the presence of atypical seminiferous tubules in 3 of 18 individuals and the presence of ovarian follicles in 3 of 18 individuals. No germinal elements were seen in 12 individuals. The gonads in the majority (8/11) of day-old female poults from treated eggs showed the presence of atypical seminiferous tubules. Three of 11 individuals had structures characterized as disorganized or degenerate follicles. Between the day of hatch and 6 wk, gonads in an increasing proportion of female chickens from Fadrazole (R)-treated eggs had normal appearing ovarian follicles. A similar trend was seen in the female turkeys between hatch and 12 wk of age. There were no differences in BW of female chickens hatched from Fadrazole (R)-treated eggs and those from control eggs between the day of hatch and 6 wk of age. The pectoral muscle mass and fat pad weights of these birds did not differ. In one experiment, the BW of female turkeys hatched from Fadrazole (R)-treated eggs was significantly greater than that of controls and equal to that of males at 3 and 6 wk of age. Thereafter, both types of females were of equal weight and significantly lighter than males. Fadrazole (R) treatment did not affect pectoral muscle mass of either sex of turkeys.