Inhibition of adrenal steroidogenesis, food restriction and acclimation to high ambient temperatures in chickens.

1. White Plymouth Rock chickens placed under 60% food restriction or ad libitum feeding, with or without metyrapone treatment, from either 4 to 6 (early) or 24 to 26 (late) d of age were exposed to high ambient temperatures (35 +/- 2 degrees C) from 36 to 43 d of age. 2. Stress attributable to fasting was not manifested through leucocytic alteration when food-restricted chicks were supplemented with an adrenal blocking chemical, metyrapone. 3. Provision of metyrapone during the fasting period resulted in inferior compensatory growth during refeeding. 4. Exposure to high temperatures from 36 to 43 d of age did not cause an elevation in the heterophil:lymphocyte (H/L) ratios of chicks that had eaten metyrapone-treated food ad libitum during the neonatal stage. 5. During heat exposure, chicks that had been subjected to early 60% restriction with non-metyrapone-treated food had lower H/L ratios and improved resistance to marble spleen disease infection.