Intensive broiler (meat) chicken production now exceeds 800 million birds each year in the United Kingdom and 2 × 1010 birds worldwide1, but it attracts accusations of poor welfare2,3. The European Union is currently adopting standards for broilers aimed at a chief welfare concern—namely, overcrowding—by limiting maximum ‘stocking density’ (bird weight per unit area). It is not clear, however, whether this will genuinely improve bird welfare because evidence is contradictory4,5,6,7,8,9,10. Here we report on broiler welfare in relation to the European Union proposals through a large-scale study (2.7 million birds) with the unprecedented cooperation of ten major broiler producers in an experimental manipulation of stocking density under a range of commercial conditions. Producer companies stocked birds to five different final densities, but otherwise followed company practice, which we recorded in addition to temperature, humidity, litter and air quality. We assessed welfare through mortality, physiology, behaviour and health, with an emphasis on leg health and walking ability. Our results show that differences among producers in the environment that they provide for chickens have more impact on welfare than has stocking density itself.
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We thank Banham Poultry Ltd, Dove Valley (Ashbourne) Ltd, Faccenda Group (including Webb Country Food Group), Grampian Country Chicken, L&M Food Group, Moy Park Ltd, O'Kane Poultry Ltd, G. W. Padley Poultry Ltd, Rose Brand Poultry (including Skovsgaard) and Two Sisters Ltd (including Premier Farming) for participation; and P. Harvey for comments on the manuscript. We thank Defra for funding. M.S.D. conceived the project, made links with the companies, obtained funding, designed the protocols, ran the first trial, took part in about 25% of subsequent trials and largely wrote the paper. C.A.D. advised on the experimental design and undertook much of the statistical analysis. T.A.J. took over the running of the project from trial 2, collected and collated data from all subsequent trials, did the preliminary statistical analysis and collaborated in writing the paper.
The authors declare that they have no competing financial interests.
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