Development of feather pecking in relation to light intensity

Medium heavy laying hens (ISA Brown) were reared on litter floor in a cross -over experiment with four treatments of age X Light intensity: 3 or 30 lux from 0 to 15 weeks of age and 3 or 30 lux from 16 to 46 weeks. Feather pec king and other behavioural activity were recorded by focal animal and time sampling at 10, 28 and 45 weeks. Pecks directed to the feathers of pen-mate s were counted and classified into gentle pecks or severe pecks (feather pu lling). The overall result of the pecking observations during rearing showe d that gentle pecks were approximately 20 times more frequent in 3 than in 30 lux, whereas severe pecks were 2-3 times more frequent in 30 lux. Genera lly, these effects were confirmed by both the time sampling and the focal a nimal sampling. The mortality in the period from 16 to 46 weeks was signifi cantly higher in higher light intensity (30.6 vs. 5.8%). The higher frequen cy of severe feather pecking at the high light intensity is in accordance w ith other studies, while the development of stereotypic gentle pecking at 3 lux is a new finding. We suggest, that low light level impaired the birds' ability to identify environmental cues during early development. Consequen tly, birds increased their exploratory pecking in order to compensate. This resulted in the development of stereotypic pecking, that persisted to the end of the experiment. Severe feather pecking in 30 lux resulted in more de teriorated plumage condition at 11 and 28 but not at 46 weeks. Severe feath er pecking might have evolved into cloacal cannibalism during the laying pe riod. We conclude that the development of gentle respectively severe feathe r pecking are influenced differently by the environment (light intensity) a nd this finding emphasises the importance to separate these types of feathe r pecking in future studies. (C) 1999 Elsevier Science B.V. All rights rese rved.