Modification of fear in domestic chicks, Gallus gallus domesticus, via regular handling and early environmental enrichment

Abstract

Although its adaptive properties are recognized, fear can harm the welfare and performance of intensively housed poultry. Its alleviation in individually caged domestic chicks via the independent or integrated application of regular handling and environmental enrichment regimes was investigated. The test situations incorporated varying degrees of exposure to novel, inanimate stimuli and of human involvement. Enrichment reduced freezing and avoidance of a novel object introduced into the home cage, accelerated emergence from a sheltered area into an exposed, unfamiliar one and increased vocalization, ambulation and pecking in an open field or novel environment. It also reduced the chicks' avoidance of a nearby, visible experimenter and attenuated their tonic immobility reaction to manual restraint. Such wide-ranging effects suggest that environmental enrichment may have modified general, non-specific fearfulness. Regular handling also attenuated the chicks' tonic immobility responses and their avoidance of the experimenter but it exerted few other detectable effects and there was no demonstrable effect of handling in the presence of enrichment. These findings are consistent with the suggestion that repeated gentle handling may exert its strongest influence, by facilitating habituation to human beings rather than by reducing underlying fearfulness. The implications of reduced fearfulness and other potential benefits of handling and enrichment procedures are discussed.