Jung, L., Knierim, U. 2019. Differences between feather pecking and non-feather pecking laying hen flocks regarding their compliance with recommendations for the prevention of feather pecking – A matched concurrent case-control design. Applied Animal Behaviour Science 219, 104839.

Feather pecking (FP) is a multifactorial problem in all housing systems. Using a case-control design we wanted to determine a set of variables which may be decisive for a flock to become case or control. At the same time, we expected that the prevention of feather pecking not only depends on certain factors, but also quantitatively on the extent of compliance with recommendations. Data from three cross-sectional studies were pooled, from which 165 flocks were allocated to cases (FP problem flocks) or controls (no FP problem). Control flocks had at least 98% of hens with a very good or nearly complete feather cover whereas in case flocks 10% or more of the hens had highly damaged feathers or featherless areas ≥ 5 cm² in at least one body region. From 32 potential preventive factors that had been recorded in all data sets, 18 factors passed univariable pre-selection and were presented to forward logistic regression analysis. The resulting model for 137 flocks (due to missing values) explained 41% of the variance, correctly classified 77% of cases and comprised four variables with an effect size of f = 0.8. A higher stocking density increased the likelihood of a ‘FP-problem’ whereas the presence of wooden perches and a littered veranda lowered it. Unexpectedly, a higher drinking place/hen ratio also predicted a FP problem. The results concerning wooden perches and drinking place/hen ratio might be due to indirect effects and should be further investigated. Non-FP flocks complied on average with 46.5% of recommendations (from a list of 13 factors), which was greater than FP-flocks (42.5%, P =  .036, U = 2537.500, n = 165, Mann-Whitney-U test, dCohen = 0.327). We conclude that the number of fulfilled recommendations as well as the combination of specific measures such as provision of a covered veranda with dry litter or reduced stocking density are important to prevent FP.