The effect of stocking density, flock size and modified management on laying hen behaviour and welfare in a non-cage system

The current large-scale experiment aimed to study laying hen behaviour under commercial stocking densities, flock sizes and management practices using a replicated design.Thirty-six flocks of beak-trimmed Shaver laying hens (113,400 birds in total), six flocks per treatment, were housed within commercial single-tier aviary systems. The six treatments comprised different combinations of stocking densities (low: 7 birds m−2, medium: 9 birds m−2, high: 12 birds m−2), flock sizes (small: 2450/3150 birds, large: 4200 birds) and management conditions (standard and modified). Bird behaviour (incidence of feather pecking, aggression, preening, dustbathing and allopreening) was recorded directly by an observer when birds were approximately 32, 48 and 60 weeks of age.The initial level of feather pecking and aggression was highest in the low stocking density. Feather pecking and aggression increased with age but only in the high stocking density treatments. In the high stocking density treatments more aggression, preening and allopreening were recorded in small flocks than in large flocks and especially the small flocks under standard management conditions showed higher levels of feather pecking and aggression by the end of the laying cycle. This effect of small, high density flocks on feather pecking and aggression was counteracted by modified management conditions.Behavioural observations in this study did not show that the welfare of laying hens was compromised by housing them at 12 birds m−2, in comparison with birds housed at 9 or 7 birds m−2 in single-tier aviary system. However, modifications in management decreased feather pecking and aggression.