Use of adrenocorticotropin challenges to indicate chronic stress responses of laying hens in several housing alternatives

The use of adrenocorticotropin (ACTH) challenges was tested as an indicator of the level of physiological stress response of laying hens in several housing alternatives. Single Comb White Leghorn (SCWL) hens were challenged with intravenous ACTH injections (either .33, 1.0 or 3.0 IU/kg body weight). Plasma corticosterone (CORT) concentrations taken at intervals from 10 to 180 min following ACTH challenges revealed CORT response curves which peaked within 30 min at 34-, 54- and 60-fold increases over pre-challenge CORT levels with doses of .33, 1.0 and 3.0 IU/kg ACTH, respectively. Peak CORT levels for 1.0 and 3.0 IU/kg of ACTH did not differ; however, CORT levels for 1.0 IU/kg ACTH were significantly elevated above the peak for .33 IU/kg ACTH. Laying hens housed in cage and floor management alternatives were challenged with .33 and 1.0 IU/kg of ACTH after 10 months of lay. Cage management treatments were 3, 4 or 5 hens per cage and floor treatments with hens kept at 2 densities. Significant differences in the ACTH-induced CORT response between management alternatives could be detected following injection of .33 IU/kg ACTH, but not with the higher ACTH dose (1.0 IU/kg). These studies demonstrated that the CORT response to the lower dose of ACTH seemed to be more effective in assessing management differences, but further clarification may be necessary before ACTH challenges can be accurately used to evaluate physiological stress responses of laying hens housed in different conditions.