The stress of not being able to perform dustbathing in laying hens.

The stress of not being able to perform dustbathing was studied in small groups of laying hens. The birds were reared and kept for 2.5 years in cages with either sand ("sand birds") or wire floors ("wire birds"), and subsequently deprived of sand (sand birds) or given access to sand (wire birds). Before this change, wire birds had a higher incidence of unilateral wing/leg stretching and stereotypic pecking compared to sand birds; however, there was no difference in corticosterone concentrations. Deprivation of sand in the sand birds resulted in a total absence of dustbathing and in a significant increase in corticosterone concentrations. Although the wire birds dustbathed on the wire before the change of floors, there was a significant increase in the incidence of dustbathing after sand was provided, but no changes in the concentrations of corticosterone. Threats and allopecks decreased in the wire birds after access to sand, whereas no changes were found in the sand birds. Stereotypic pecks on feathers were absent in the sand birds, but were frequent in most of the wire birds both before and after they were given sand. Also, in the wire birds, all feather pecking (stereotypic and nonstereotypic) was positively correlated with the concentration of corticosterone, and this kind of pecking may, thus, be an expression of stress in laying hens. We conclude that the nonperformance of dustbathing behavior is associated with the experience of stress.