Chronic welfare restrictions and adrenal gland morphology in broiler chickens.

Gait problems constitute an important and chronic welfare restriction for broiler chickens. The objective of the present study was to determine if adrenal gland morphology indicates chronic welfare restrictions in broiler chickens, using gait problems as the stressor. Sixty-six birds raised on a commercial unit were selected at 40 d of age and separated into groups according to gait score. One group was apparently healthy birds (AH) with gait scores of 0 to 2, and the other group had birds with gait problems (GP) that showed gait scores of 4 to 5. Birds were slaughtered and weighed, and their adrenal glands were measured and weighed; proportions of medullary and adrenocortical tissues, and lymphatic tissue and blood vessels were studied. GP birds had lower BW when compared to AH birds, and when adrenal gland weight values were adjusted to BW, a greater relative adrenal weight was observed for the GP group. Adrenals from GP birds also presented a higher proportion of blood vessels when compared to AH birds. These results might indicate increased adrenal activity and evidence of the inflammatory process as a consequence of chronic stress. Results showed that gait problems caused significant adrenal gland changes, suggesting a possible role for the study of adrenal gland morphology as an indicator of chronic welfare problems in broiler chickens.