Feather pecking phenotype affects behavioural responses of laying hens

Feather pecking (FP) is a major welfare and economic issue in the egg production industry. It involves hens pecking and pulling at feathers of conspecics, thereby negatively aecting welfare. Behavioural characteristics, such as fearfulness, have been related to FP. Although many studies have identied dierences in fearfulness between lines that dier in FP, the relationship between actual FP behaviour (i.e. FP phenotypes) and fearfulness is not well understood. erefore, we compared responses of birds with diering FP phenotypes to several behavioural tests at young and adult ages. We used birds from a genetic line selected for high feather pecking. FP phenotypes of individual birds were identied via FP observations at 3-4, 12-13, 15-16 and 28-29 weeks of age. e total number of severe feather pecks (SFP) given and received over two subsequent weeks was used to categorize birds as feather peckers (P, SFP given >1), feather pecker-victims (P-V, SFP given and received >1), victims (V, SFP received >1) or neutrals (N, SFP given and received 0 or 1) at each age point. Birds were tested individually in a novel environment (NE) test at 4 weeks of age, an open eld (OF) test at 15 weeks of age and a tonic immobility (TI) test at 13 and 28 weeks of age. Experimenters were blinded to the phenotypes. Data were analysed using linear mixed models, with phenotype and batch as xed factors and pen as a random factor. Test time was added as a xed eect for the NE and OF test. Experimenter was added as a xed eect for the NE and TI test. Testing order was included as a xed eect for the TI test. Phenotype eects were tested for each behavioural test and age separately using the most recent FP phenotype categorization. FP phenotype aected the number of ight attempts (F3, 119=3.18, P<0.05) during the NE test, where victims showed more ight attempts compared to neutrals (V=2.3 vs n=1.6; P<0.05) and tended to show fewer ight attempts compared to feather peckers (V=2.3 vs P=2.7; P<0.1). FP phenotype further tended to aect step frequency (F3, 75=2.64, P<0.1) during the OF test, where feather peckers tended to walk more compared to neutrals (P=24.6 vs n=15.7; P<0.1). No FP phenotype eects were found for the TI test. Feather peckers tended to show more active responses (i.e. tended to show more ight attempts compared to victims and tended to walk more compared to neutrals), which could suggest lower fearfulness, compared to victims at 4 weeks of age and compared to neutrals at 15 weeks of age. ese ndings give rst indications that FP phenotypes seem to dier in fearfulness. It should be noted that we only found dierences in the NE and OF test, where behavioural responses could also be related to activity or coping style. Further research is needed to identify whether FP phenotypes dier in activity and whether they can be classied into dierent coping styles.