Development of feather pecking in relation to light intensity

Abstract

Medium heavy laying hens (ISA Brown) were reared on litter floor in a cross-over experiment with four treatments of age×light intensity: 3 or 30 lux from 0 to 15 weeks of age and 3 or 30 lux from 16 to 46 weeks. Feather pecking 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-mates were counted and classified into gentle pecks or severe pecks (feather pulling). The overall result of the pecking observations during rearing showed 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. Generally, these effects were confirmed by both the time sampling and the focal animal sampling. The mortality in the period from 16 to 46 weeks was significantly higher in higher light intensity (30.6 vs. 5.8%). The higher frequency of severe feather pecking at the high light intensity is in accordance with 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. Consequently, 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 deteriorated plumage condition at 11 and 28 but not at 46 weeks. Severe feather pecking might have evolved into cloacal cannibalism during the laying period. We conclude that the development of gentle respectively severe feather pecking are influenced differently by the environment (light intensity) and this finding emphasises the importance to separate these types of feather pecking in future studies.