Opportunities and challenges of modern mobile housing systems for laying hen welfare - an observational study

A variety of commercial mobile houses for laying hens are emerging as innovative housing systems. However, only limited research on their potential for animal welfare is currently available. In this study, we compared welfare outcomes between different categories of mobile houses and with stationary systems, and aimed to identify welfare-relevant challenges associated with managing the mobile housing systems. Over a period of two years, animal-based welfare indicators (MTool©) were repeatedly assessed on 42 farms with 48 mobile houses across four size and mobility categories: wheel-based small, medium, large, and skid-based, with 200 to 2,059 hens/house. For the comparison with stationary housing, repeated MTool©-assessments from five farms with and four farms without free-range access with 2,250 to 6,000 hens/flock were used. Prevalences of plumage damage and injuries were significantly lower in mobile housing, while keel bone damage was similarly prevalent across all housing systems. The extent of footpad dermatitis was unaffected by mobile versus stationary systems. More hens had comb and wattle injuries in mobile houses, which warrants further investigation into the influences on agonistic pecking. Among others, adequate feeding space per hen must be guaranteed within the mobile house, even if this entails additional manual labor. Further key challenges of mobile housing include the protection from predators, enrichment when free-range access must be restricted temporarily due to avian influenza, climate control at all times, and optimal relocation frequency of the mobile units. Among the four mobile housing categories, relatively few differences were found. They concerned prevalences of pale combs, footpad dermatitis and slight differences in plumage soiling at the back, possibly reflecting differences in free-range accessibility, perch and litter condition and manure collection. The mostly large range in prevalences of welfare issues between flocks suggest that appropriate management is more important than mobile housing categories which all have the potential to provide for good laying hen welfare.