Endocrine effects of castration followed by androgen replacement and ACTH injections in the male domestic duck (Anas platyrhynchos L.)

Adult male ducks submitted to natural lighting were bilaterally castrated in the winter. They were then repeatedly injected as follows: testosterone propionate (= TP; 5 mg/day and male) + long-acting ACTH (20 IU/day and male): N = 6; TP + saline: N = 6; oil + ACTH: N = 5; finally oil + saline: N = 4. Blood samples of these birds were individually assayed at different times following the start of the treatments for LH, FSH, and corticosterone. Three days following castration, LH as well as FSH levels were significantly above the levels in a sham-operated group. By that time LH levels had increased significantly more than FSH levels, a difference which disappeared later on in the experiment. TP administration caused gonadotrophins to fall below values of sham-operated birds. This drop was much more important for LH than for FSH. ACTH treatment, while inducing important and time-dependent variations in the corticosterone levels, did not affect either LH or FSH levels. Measurement of gonadotrophins three times during the day did not enable the demonstration of daily variations in any group.