Abstract
Appropriate rearing is essential for ensuring the welfare and productivity of laying hens. Early experience has the potential to affect the development of fearfulness. This study tested whether rearing in aviaries, as opposed to cages, reduces the fearfulness of laying hens after transfer to furnished cages. Fear responses were recorded as avoidance of a novel object in the home cage. Lohmann Selected Leghorns were reared in an aviary system or conventional rearing cages and then transported to furnished cages at 16 weeks, before the onset of lay. Observations of a selection of birds were conducted at 19 (N = 50 independent cages) and 21 (N = 48 independent cages) weeks of age. At 19 and 21 weeks, cage-reared birds showed higher levels of fearfulness indicated by spending more time away from the novel object compared to aviary-reared birds. These results suggest that rearing in an enriched aviary environment reduces fearfulness up to the fifth week after transfer to a new housing system, compared to rearing in cages.
Highlights
Under natural conditions, fear normally functions to protect animals from dangerous situations, and thereby increases their chances of survival [1]
Duration of Time Spent in Zone 1 For the duration of time spent in zone 1, in which the novel object was situated, there was no effect of treatment (F1,44 = 2.6227; p = 0.1125), tier (F2,44 = 0.3290; p = 0.7214), or the interaction between them (F2,44 = 0.5828; p = 0.5626)
Duration of Time Spent in Zone 1–2 When combining the time spent in zone 1 and 2, the aviary-reared birds tended to spend more time closer to the novel object compared to the cage-reared birds (F1,44 = 3.0103; p = 0.0897; aviary-reared: 248.071 ± 137.87 s; cage-reared: 170.045 ± 147.285 s)
Summary
Fear normally functions to protect animals from dangerous situations, and thereby increases their chances of survival [1]. Under production conditions, exaggerated fear is a potent stressor associated with activation of the hypothalamic–pituitary–adrenocortical axis. The early environment may have a great impact on the development of fearfulness and associated activation of the hypothalamic–pituitary–adrenocortical axis in response to stressors [6, 8,9,10,11]. Exposure to increased environmental complexity during rearing has been found to reduce fearfulness during adulthood in several species, including mice [12], pigs [13], and chickens [14]. Few studies have tested for effects of the rearing system on later fearfulness in laying hens. A study comparing floor-housed adult birds reared on sand, straw, or wire from 0 to 4 weeks found that birds reared on wire were the most fearful, as indicated by longer durations of induced tonic immobility [14]
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