Age-related changes in fear, sociality and pecking behaviours in two strains of laying hen

1. Two lines of commercial hybrid layers ( Tetra and ISA Brown) were reared from hatch to 30 weeks of age in groups of 8. The objectives of the experi ment were to evaluate the significance of the different selection practices involved in the development of the lines and to assess the potential assoc iation between selected behavioural states and the potential for feather da mage and cannibalism. 2. Behavioural tests related to fear ( tonic immobility, novel object, open field), sociality ( runway, proximity in the home pen) and pecking ( feath er bunch and focal observations of inter-bird and environmental pecking) we re conducted at 0 to 2, 5 to 7, 12 to 14, 19 to 21 and 29 to 31 weeks of ag e. Scan sampling of general behaviour was also conducted at these ages. 3. Underlying sociality was greater in Tetras than in ISA Brown hens. 4. There were no apparent overall strain differences in fearfulness althoug h ISA Brown hens showed significantly longer tonic immobility fear reaction s than Tetras at 31 weeks of age. 5. ISA Brown hens gave and received more gentle pecks than Tetra hens where as preening was commoner among Tetras. There were no strain differences in the number of pecks at litter or food. 6. As birds aged they showed less avoidance of novel objects and Tetras, th ough not ISA Browns, showed progressively shorter tonic immobility response s. Birds of both strains spent less time resting, more foraging ( pecking a nd scratching) and pecked more at the feather bunch at older ages. 7. Measures taken in the TI, open field, runway ( social affiliation) and f eather bunch tests were stable over time whereas focal observations of peck ing at hens and the environment were not. 8. Factor Analysis showed that 3 factors defined by the novel object test, environmental pecking and pecking at a feather bunch explained most of the variation in the correlation matrix between summary measures for the 8 beha vioural traits.