Early Life in a Barren Environment Adversely Affects Spatial Cognition in Laying Hens (Gallus gallus domesticus)

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.

Uninhibited chickens: ranging behaviour impacts motor self-regulation in free-range broiler chickens ( Gallus gallus domesticus )

“…The environmental complexity of different housing conditions and internal factors such as sex, breed and animal personality are known to affect an individual's behaviour, brain morphology and cognitive abilities [14,[40][41][42][43][44]. In our study, animals living under the same conditions but with different propensities to range showed different levels of motor self-regulation.…”

Unraveling important genetic associations and differential methylation profiles using reduced genome sequencing in chickens

“…In addition to fear responses, these rearing conditions also associate with different levels of cognitive capabilities observed later in life in birds from the same groups as in the present experiment (TAHAMTANI et al, 2015).…”

“…Epigenetic changes are defined as accessory chemical modifications of the DNA that regulate gene expression and are mitotically stable (SKINNER et al, 2010). These modifications include DNA methylation or hydroxymethylation of CG dinucleotides, chemical modifications of histones, interaction of DNA with small RNAs, or states of chromatin condensation (FEIL;FRAGA, 2011;TEPEREK-TKACZ et al, 2011;DENHAM et al, 2014). Altering epigenetic states can lead to distinguishable phenotypic consequences such as changes in the coat color (DOLINOY et al, 2007) or increased propensity to diseases (GUERRERO-BOSAGNA; SKINNER, 2012).…”

“…These two different rearing conditions are likely to differ with regards to the amount of stress to which birds are exposed, as suggested by the observation that they cause long-term differences in fearfulness (BRANTSAETER et al, 2016) and cognitive function (TAHAMTANI et al, 2015).…”

“…Previous studies have shown that chickens reared in a complex aviary system are less fearful, use elevated areas of the pen more often as adults (BRANTSAETER et al, 2016), and have better spatial working memory (TAHAMTANI et al, 2015) than laying hens reared in a simpler cage environment (BRANTSAETER et al, 2016).…”