Scientific Opinion on welfare aspects of the use of perches for laying hens
This opinion investigated the use of perches for laying hens in cage and non-cage systems. It is based on various activities reviewing the effects of perch height and design on hen health and welfare. Systematic and extensive literature reviews were conducted to assess the scientific evidence about hen motivation to grasp and seek elevation, and the appropriate height of perches as well as other features (position, material, colour, temperature, shape, width and length). In addition, an expert knowledge elicitation (EKE) exercise was run with technical hearing experts to discuss and prioritise the various design aspects of perches. Overall, the body of literature on perches is limited. Relevant features of perches are often confounded with others. In the literature, the most commonly used animal-based measures to assess perch adequacy are keel bone damages, foot pad lesions and perch use by hens. Overall, hens seek elevation during the day as well as during the night, when they select a site for roosting. Elevated perches allow hens to monitor the environment, to escape from other hens, avoid disturbances and improve thermoregulation. For night-time roosting hens show a preference for perches higher than 60cm compared with lower perches. However, elevated perches can have negative consequences with increased prevalence of keel deformities and fractures. The risk of injury increases when hens have to jump a distance of more than 80cm vertically, horizontally or diagonally to reach or leave a perch, or jump an angle between 45 and 90° (measured at the horizontal plane). Material, shape, length and width of the perch also influence perch preference by hens. The EKE exercise suggests that an adequate perch is elevated, accessible and functional (providing sufficient overview). The opinion concludes that for the design of an adequate perch, different features of perches need to be further investigated and integrated.