Physiological stress was studied in broilers using a new model employing co
ntinuous release of adrenocorticotropin (ACTH). A total of 42 adaptive resp
onse parameters were evaluated. A treatment response ratio, P-value transfo
rmation, and stress score were determined for each parameter. The treatment
response ratio was calculated by dividing the maximum response of the ACTH
-treated birds for each parameter by the average response of control (CON)
birds in all cases in which maximum response of ACTH-treated birds exceeded
the average response of CON. This treatment response ratio is designated h
ereafter as ACTH/CON ratio. In those cases in which average response of CON
exceeded maximum response of ACTH-treated birds, the reciprical equation w
as employed (i.e., CON/ACTH ratio). Probability value transformations were
determined by transforming P-values as follows: NS P-values or those exhibi
ting significance at values less than probability of 5% were expressed as P
< 0.05 = 1, P-values exhibiting significance between 0.05 and 0.02 were ex
pressed as P at 0.05 to 0.02 = 2, and P-values exhibiting significance at p
robabilities of 1% or less were P < 0.01 = 4. Each stress score was calcula
ted as treatment response ratio times P-value transformation. The 42 respon
se parameters were assigned to one of four adaptive categories, and these w
ere morphologic, endocrine, and blood metabolites; digestion and metabolism
; and reticuloendothelial responses. The endocrine and blood metabolites ca
tegory had the highest average of the four stress response categories, and
five of the top ten parameters were found in this category.