Performance of laying hens in a cognitive bias task : effect of time since change of environment
In the debate on laying hen welfare, and specifically housing conditions, the main focus has been on physiological and behavioural measures. What is lacking is knowledge of how the hen experiences the situation – her state of mind. This study is an attempt to gain insight into the private mental sta...
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| Formato: | M2 |
| Lenguaje: | Inglés sueco |
| Publicado: |
SLU/Dept. of Animal Environment and Health (until 231231)
2010
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| Sumario: | In the debate on laying hen welfare, and specifically housing conditions, the main focus
has been on physiological and behavioural measures. What is lacking is knowledge of how
the hen experiences the situation – her state of mind.
This study is an attempt to gain insight into the private mental states of former battery
hens. It uses a cognitive bias method based on spatial judgement, i.e. judgement of a
ambiguous stimulus placed spatially in between a reinforced and an unreinforced stimulus.
This method has previously shown differences in judgement by animals in enriched versus
poor housing. The aim of the current study was to measure such biases expressed by hens
two months compared to four months after moving from battery cages to littered pens. The
animals were also tested in a novel object task for a measure on general anxiety, and their
plumage condition was scored. Their social rank was established by testing penmates in
pairwise competitions over a limited food resource.
The hens showed longer latencies to reach the intermediate position four months after
leaving the cages, compared to two months after. Possible reasons for this could be that the
positive effects of the improved environment were largest when the hens had recently left
the battery cages, with the effect of the improvement gradually being diminished or even
reversed. It is likely that novelty in itself is positive to hens, and a static environment
becomes boring in time even though it is far more complex than a battery cage.
No difference was found in the reactions to ambiguous cues by hens of different social
status. A strong correlation was found between feather score and social dominance.
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