The response of the immature fowl to multiple injections of adrenocorticotrophic hormone.

1. Treating chicks, from 1 d or 5 weeks of age with ACTH three times weekly for 3 weeks depresses growth and causes adrenal hypertrophy at dose rates of 30 IU/kg or more, and depletion of adrenal cholesterol (greater than 10 IU/kg). 2. Treating chicks five times weekly at a dose rate of 30 IU/kg was as effective as a dose of 120 IU/kg three times weekly. 3. Plasma glucose and FFA concentrations of chicks treated thrice weekly with 120 IU ACTH/kg for 3 weeks were within the normal range. 4. Rhode Island Reds were more sensitive to ACTH than Light Sussex. 5. Adrenal cholesterol stores in normal chicks show significant variations with season.