Abstract
Spatial cognition in vertebrates is adversely affected by a lack of environmental complexity during early life. However, to our knowledge, no previous studies have tested the effect of early exposure to varying degrees of environmental complexity on specific components of spatial cognition in chickens. There are two main rearing systems for laying hens in the EU: aviaries and cages. These two systems differ from one another in environmental complexity. The aim of the present study was to test the hypothesis that rearing in a barren cage environment relative to a complex aviary environment causes long-lasting deficits in the ability to perform spatial tasks. For this purpose, 24 white Dekalb laying hens, half of which had been reared in an aviary system and the other half in a conventional cage system, were tested in a holeboard task. Birds from both treatment groups learnt the task; however, the cage-reared hens required more time to locate rewards and had poorer levels of working memory. The latter finding supports the hypothesis that rearing in a barren environment causes long-term impairment of short-term memory in chickens.
Highlights
Animals must be able to perceive, store, and retrieve information in order to navigate their environment and maximize the ratio of benefits to costs
With the exception of the three birds that did not learn the task, the effects of phase indicated that the holeboard task was a valid approach to quantifying working memory, general working memory, and reference memory in laying hens
This was confirmed by higher average scores for working memory, general working memory, and reference memory during cued acquisition and over-training than during uncued acquisition
Summary
Animals must be able to perceive, store, and retrieve information in order to navigate their environment and maximize the ratio of benefits to costs. Natural and artificial selection are likely to favor individuals that program the allocation of resources to cognitive function, depending on the environment encountered during the early stages of development. These arguments emphasize the ultimate mechanisms underlying developmental plasticity, as suggested by the predictive adaptive response hypothesis [6]. A poor environment during early life may incur costs because of a lack of the stimulation necessary for optimal development, as suggested by the “silver spoon” hypothesis [7, 8] Both lines of argumentation suggest that early life in a simple environment should produce individuals with reduced cognitive ability compared to those raised in a more complex environment. One would predict that birds exposed to a barren environment during early life would have poorer memory capacity
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