Effect of exogenous corticotropin and climatic conditions on bovine adrenal cortical function.

Interactions between three climatic conditions and exogenous adrenocorticotropin (200 IU) or saline on glucocorticoids of plasma were tested in six pregnant Holstein heifers. Animals were under cold (5 C, 30% relative humidity), thermoneutral (18 C, 50% relative humidity), and hot (35 C, and 80% relative humidity) conditions. Effects of treatment, interactions of environment with treatment, and environment with treatment with interval on glucocorticoids of plasma were measured through timed intervals of blood collection at pre- and postintravenous injection of a treatment solution. Adrenocorticotropin elevated corticoid concentrations in plasma, but interactions of environment with treatment and environment by treatment by sampling interval were nil for responses of corticoids in plasma.