Problem behaviors in adult laying hens - identifying risk factors during rearing and egg production.

Feather pecking, toe pecking, cannibalism, smothering, social clumping, hens laying eggs outside the nest boxes, and reduced feather quality are examples of problem behaviors and consequences reported by egg producers. The aim of this study was to identify rearing- and production-related risk factors associated with producer-reported problem behaviors in Norwegian layer flocks. Questionnaires were distributed to 410 egg producers nationwide, and 120 producers responded to the survey (response rate 29%). After exclusion of data that did not comply with the instructions, the final dataset included 78 flocks (19%). The survey covered questions about the farm, the flock's production results, the housing environment, climate and management routines, and the behavior of the birds from 16 wk of age until the flock was euthanized at 70-80 wk of age. The individual problem behaviors were combined to generate a continuous index variable called "problem behavior", ranging from 0 (none) to 8 (all the listed problem behaviors) reported. Multilevel linear regression models were applied to evaluate associations between the index and selected risk factors during rearing and production. The primary predictor was housing system during egg production: producers with aviary flocks on average (± standard deviation) reported 1.6 (± 0.60) more problem behaviors compared to producers with furnished cages (P < 0.001). Within aviaries (n = 40), producers, on average reported 1.7 (± 0.50) more problem behaviors in flocks that experienced problems with climatic conditions, compared to flocks without climatic problems (P = 0.001). For respondents with furnished cages (n = 30), on average 1.1 (± 0.50) fewer problem behaviors were reported in farms with ≥ 7,500 birds compared to farms with < 7,500 birds (P = 0.027). In conclusion, this is the first study assessing management and housing factors during the rearing and laying phase associated with problem behaviors as reported by Norwegian egg producers. As this study relied on producer reported observations, future studies are needed to investigate whether objective measurements can verify these results.