Early prenatal treatment of ewes with testosterone completely masculinises external genitalia of female offspring but has no effects on early body weight changes.

Abstract

Treatment of pregnant ewes from day 20 of gestation with 100 mg implants of crystalline testosterone did not cause masculinisation of genitalia or affect growth rates of female lambs. Prenatal treatment from day 20 of gestation with testosterone propionate (1.2 g in divided doses for four weeks) or testosterone cypionate (600 mg in 3 doses over three weeks) completely masculinised the external genitalia of female lambs producing a ventral penis and scrotum with no external vaginal opening: ovaries and uteri were normal. Single male lambs were significantly heavier than female lambs during a 16 week measurement period, but masculinised female lambs were not different from controls. In the twin lamb groups, there were no differences between male and female or treated and control lambs. Body weights of castrated male lambs born as twins were not different from entire controls. It was concluded that testosterone treatment of developing lambs from 20 to 65 days of gestation produces complete masculinisation of external genitalia of female lambs but does not affect body weight during the first 16 weeks of age.