The development of feather pecking behaviour and targeting of pecking in chicks from a high and low feather pecking line of laying hens

Large individual differences between adult laying hens in their propensity for feather pecking are known to exist. However, not much research has been carried out into the individual differences concerning the development of feather pecking behaviour. The purpose of this study was to investigate whether contrasting levels of feather pecking, observed among adult birds from two lines of laying hens, already occur at an early age. Furthermore, an important question to be discussed was whether different behavioural systems may be related to the occurrence of feather pecking. Therefore, this study consisted of studying and comparing the behaviour of White Leghorn laying hens from a high (HFP) and low feather pecking line (LFP) during the first 8 weeks of life. Chicks were reared in litter-floor pens and were kept in groups of five animals per line (12 groups per line).HFP chicks showed significantly higher levels of gentle feather pecking (gentle FP) than LFP chicks at the age of 14 and 28 days. Furthermore, HFP chicks spent significantly more time preening than LFP chicks on days 14, 28 and 41. Duration of foraging behaviour and feeding behaviour was significantly higher in the LFP line compared to the HFP line on days 41 and 56 and days 28, 41 and 56, respectively. HFP chicks showed a significant negative correlation between gentle FP and preening on days 3 (r=-0.49) and 41 (r=-0.86). In the LFP line duration of feeding correlated negatively with gentle FP on day 3 (r=-0.63). A principal component analysis (PCA) revealed that in the HFP line, gentle FP and preening exhibited high and opposite loadings on the same component at all ages, whereas feeding consistently loaded on the other component. This outcome contrasted with that of the LFP line. In this line feeding predominantly loaded on the same principal component as gentle FP, with loadings opposite to those of gentle FP, whereas preening showed the same loadings as gentle FP, on days 3 and 41.In conclusion, differences in feather pecking behaviour between HFP and LFP chicks can already be observed at a very early age during development. Furthermore, our results indicate that HFP and LFP chicks differ in the way pecking behaviour is targeted. This difference could be related to the existence of a difference in underlying motivational system controlling the development of feather pecking between the two lines