Influence of Increased Freedom of Movement on Welfare and Egg Laying Pattern of Hens Kept in Aviaries

Simple Summary The laying hen industry is shifting from cages to alternative housing systems (such as aviaries) to address societal concerns regarding animal welfare. However, it is important to understand the hens' needs in these systems, in terms of space use and behaviour, to promote their welfare and avoid drawbacks. Therefore, we examined the effects of three different structural modifications (addition of ramps and/or removal of internal partitions) to increase the hens' freedom of movement in a commercial aviary system. Higher freedom of movement resulted in positive effects on feather conditions and the possibility of choosing between the aviary tiers according to the hens' preferences. Laying hen producers may therefore adopt some of these structural modifications in aviary systems to enhance the welfare of hens. This work investigates the effects of structural modifications on the welfare level and laying patterns of hens in a three-tier commercial aviary system. Four experimental groups were used: C (control, housed in a traditional aviary); LM (longitudinal movement, in which internal partitions were removed); VM (vertical movement, in which ramps were installed); and FM (freedom of movement, both LM and VM modifications). Hens showed worse body condition scores (p < 0.05) in all the modified aviaries, while plumage condition was improved in FM but worsened in VM (p < 0.05). No significant effect was observed on egg deposition patterns, egg quality or keel bone damage. When ramps were available (VM and FM groups), hens reduced the number of flights and increased the number of walks from 0.52 to 7.7% of the displacements on average (p < 0.05). Apart from some feather pecking concerns in VM (likely due to overcrowding in some favourite aviary areas), LM and FM seemed to facilitate animal movement and promote species-specific behaviour. It is concluded that hen welfare in aviary systems can be improved by means of tailored structural modifications. Producers may therefore adopt some of these modifications (providing ramps and/or removing vertical barriers) to enhance the welfare of hens.