Relationships between foraging and open-field activity in young chicks and feather pecking in adult birds: results of analyses using quantitative genetics and structural equation models

Feather pecking is a serious damaging behaviour in the domestic fowl. Despite intensive research, the causes of this behaviour are not fully understood. Foraging and fear are considered as important causal motivations for feather pecking in the Domestic Fowl. There exist however, contrasting results which challenge the general validity of the hypotheses. It was the aim of the present study to unravel the relationships between severe feather pecking (FPD; bouts of severe feather pecks delivered), foraging (FOR, sum of walking and litter pecking), and open-field activity (OFA; number of steps) as criterion for fear, using observations of 862 birds of a F2-cross of lines selected for high or low levels of feather pecking. Heritability, phenotypic- and genetic correlations were estimated using standard multitrait analysis. Putative causal relationships between the criteria were determined using structural equation models. It was hypothesised that both OFA and FOR influence FPD, and that OFA influences FOR. Heritability for FPD and OFA was 0.19 and 0.21 respectively. The heritability for FOR was zero. Consequently, it was not possible to estimate genetic correlation between FOR and other traits. Genetic correlation between OFA and FPD as well as all phenotypic correlations among traits were very low. Recursive effects among the traits were also low and varied between 0.01 and 0.004. The results of the F2-cross used in the present study do not support the hypotheses that FOR and OPA have a causal influence on FPD.