Open Access Minimally-Invasive Assessments of the Behavioural and Physiological Effects of Enriched Colony Cages on Laying Hens

Abstract: The well-being of laying hens in cages of 5, 10, 20 and 40-birds/cage, and enrichment with perches, nest boxes and scratch pads, was assessed using behavioral and physiological parameters. Laying hens were Lohmann Brown (n = 360) and White Leghorns (n = 360), housed from 17 to 65 weeks of age. Behavioral parameters were; the percentage of birds per cage roosting on perches, claw length (n = 288), and the percentage of eggs laid within nest boxes. Physiological parameters were; the assessment of feather cover from measurements of radiated temperatures by infrared thermography (IRT), bone mineral content of the humerus and femur by quantitative computer tomography (QCT) scans, and adrenocor-tical function as a marker of chronic stress by measurements of corticosterone concentrations in egg yolk and albumin. The majority of eggs (72.7 %) in furnished cages were laid in nest boxes. Nest use was highest in Brown hens (P < 0.03). Perch use was>80 %, but significantly less in the 10-bird cages (P < 0.0012) due to a shorter perch length. Claws were shorter on birds in cages with scratch pads (P < 0.0001). Feather insulation declined from 35 to 60 weeks of age for breast and back areas (P < 0.0001). White birds exhibited superior breast feather insulation compared to Brown birds. Egg albu-min corticosterone levels declined between 35 and 60 weeks of age (P < 0.011). There were no indications of an affect of colony size or cage enrichment on measurements of bone mineral content. The findings indicated a preference for the use of nest boxes, perches and scratch pads. Significant losses in feather insulation occur with time. A reduction in egg albu