RÉSUMÉ
BACKGROUND: Feather pecking is a well-known problem in layer flocks that causes animal welfare restrictions and contributes to economic losses. Birds' gut microbiota has been linked to feather pecking. This study aims to characterize the microbial communities of two laying hen lines divergently selected for high (HFP) and low (LFP) feather pecking and investigates if the microbiota is associated with feather pecking or agonistic behavior. METHODS: Besides phenotyping for the behavioral traits, microbial communities from the digesta and mucosa of the ileum and caeca were investigated using target amplicon sequencing and functional predictions. Microbiability was estimated with a microbial mixed linear model. RESULTS: Ileum digesta showed an increase in the abundance of the genus Lactobacillus in LFP, while Escherichia was abundant in HFP hens. In the caeca digesta and mucosa of the LFP line were more abundant Faecalibacterium and Blautia. Tryptophan metabolism and lysine degradation were higher in both digesta and mucosa of the HFP hens. Linear models revealed that the two lines differ significantly in all behavior traits. Microbiabilities were close to zero and not significant in both lines and for all traits. CONCLUSIONS: Trait variation was not affected by the gut microbial composition in both selection lines.