Effects of modifying layer cages with perches on stress physiology, plumage, pecking and bone strength of hens

This experiment evaluated the welfare of layer hens housed in cages modified with perches. Welfare was assessed on the basis of physiological measures of stress (corticosterone concentrations 'at rest' and in response to ACTH and heterophil: lymphocyte ratios) and immunological responsiveness, feather condition and cover, bone strength, claw length and between-bird pecking behaviour. Factors examined were cage modification (perches v. standard cage), tier (upper v. lower), birds (1 or 2 birds/cage) and age (commencing at 35 v. 60 weeks of age). The cages provided a floor area of 1504 cm(2). Floor pens (2.5 by 2.5 m) with 10 birds/pen served as an external control treatment. Perches improved the strength of the femur (P<0.05) compared with standard cages but bone strength was still less than in floor pens (P<0.05). There were no effects of cage modification on any of the physiological variables or liveweight (P>0.05). The only improvement in feather condition and cover within cages due to the presence of a perch was in the condition of the tail feathers which was better (P<0.05) than in a standard cage, but not as good as tail feathers in the pen treatment (P<0.001). Overall, feather condition and cover was better in the pen treatment (P<0.001) and similar in the 2 cage treatments (P>0.05). The presence of a perch resulted in longer claws than in a standard cage and floor pens (P<0.05), and significant (P<0.01) perching activity compared with floor pens. The experiment showed that perches should be considered for use in commercial laying cages as they resulted in an improvement in bone strength; there was also an improvement in tail feather condition, which is considered by some to be an advantage.