The phenotypic interrelationships between feather pecking, being feather pecked and fear criteria in White Leghorn lines selected for high and low severe feather pecking and their F2-crosses

Abstract

On the basis of observations that flocks of chickens with high incidence of feather pecking and feather damages show a high fear level, it is generally assumed that feather pecking and fear are positively correlated. This hypothesis was tested in two experiments using adult laying hens of lines selected for high (HFP) and low feather pecking behaviour (LFP) and their reciprocal crosses. A total of 60 adult birds, 30 HFP and 30 LFP, of the selection lines were used in part one of the experiment. The birds were first observed for the number of bouts of severe feather pecks delivered (FPD) and received (FPR) when kept in groups of equal numbers of both lines. Thereafter all birds were subjected to several fear tests: Tonic immobility test (TI), open- field test (OF), emerge box test (ET) and pencil test. In part two of the experiment a total of 967 birds of the F2- crosses of both lines were used. All birds were tested using the same fear tests as above at 7 days and 40 weeks of age. FPD and FPR were observed in adults only. The whole population was split for FPD in HFP and LFP using the threshold of ≥ 2 (HFP) and < 2 (LFP). HFP and LFP of the selection lines and the F2- crosses clearly differed in FPD. LFP of the selection lines received more feather pecks than HFP. There was no significant difference for FPR in HFP and LFP in the F2- crosses. In contrast to our expectation HFP from the selection lines showed a significant shorter duration of TI, shorter latency to move and to vocalize in the OF and a shorter latency to leave the emerge box, indicating lower fear. Similar results were found in the HFP and LFP of the F2- crosses for the duration of TI and latency of head appearance in the ET. Latency of the first step and to vocalize in the OF, however showed the opposite tendency. Line by age interactions appeared for the number of inductions in the TI and the latency of head emerge in the ET. There were no differences between HFP and LFP in the pencil test in both experiments. The phenotypic correlations between FPD and FPR with all fear criteria were low and not significant in both experiments. There is obviously no consistent relationship between feather pecking and fear in this population. Depending on type of fear test and age the HFP may show higher, lower or no difference in fear. Genotypes by age interactions further contribute to the variability of the results. The low phenotypic correlations among the criteria confirm this conclusion.