Abstract
Feather pecking (FP) is a stress-induced neuropsychological disorder of birds. Intestinal dysbiosis and inflammation are common traits of these disorders. FP is, therefore, proposed to be a behavioral consequence of dysregulated communication between the gut and the brain. Probiotic bacteria are known to favorably modulate the gut microbiome and hence the neurochemical and immune components of the gut-brain axis. Consequently, probiotic supplementation represents a promising new therapeutic to mitigate widespread FP in domestic chickens. We monitored FP, gut microbiota composition, immune markers, and amino acids related to the production of neurochemicals in chickens supplemented with Lactobacillus rhamnosus or a placebo. Data demonstrate that, when stressed, the incidence of FP increased significantly; however, L. rhamnosus prevented this increase. L. rhamnosus supplementation showed a strong immunological effect by increasing the regulatory T cell population of the spleen and the cecal tonsils, in addition to limiting cecal microbiota dysbiosis. Despite minimal changes in aromatic amino acid levels, data suggest that catecholaminergic circuits may be an interesting target for further studies. Overall, our findings provide the first data supporting the use of a single-strain probiotic to reduce stress-induced FP in chickens and promise to improve domestic birds' welfare.
Highlights
Feather pecking (FP) is a stress-induced neuropsychological disorder of birds
We investigated the ability of oral supplementation with a single bacterium to modulate feather pecking (FP) behavior, immune biomarkers and T cell phenotypes, as well as cecal microbial composition, the HPA axis and aromatic amino acid metabolism in birds selected for FP and exposed to chronic, repeated, unpredictable stress
Recent advances in feather pecking (FP) research in laying hens explore the role of bidirectional communication between the gut and the brain and have suggested that severe FP may be linked to neurobiological d ysfunction[35]
Summary
Feather pecking (FP) is a stress-induced neuropsychological disorder of birds. Intestinal dysbiosis and inflammation are common traits of these disorders. Chronic, multiple, and/or unpredictable, these adaptation processes may fail to return the organism to h omeostasis[2] This failure can lead to chronic disease, which is accompanied by increased hypothalamic–pituitary–adrenal (HPA) axis activity[3], severe decrease in number and function of lymphocytes T subset p rofiles[4], changes to concentrations of immune activation markers[5,6], and inflammation-induced changes in catabolism of aromatic amino acids, such as tryptophan (TRP), phenylalanine (PHE) and tyrosine (TYR)[7]. The resulting dysbiosis may disrupt the epithelial barrier, thereby increasing susceptibility to enteric infection and inflammation[34] This “leaky gut” phenomenon allows bacteria to translocate across the intestinal mucosa and activates a mucosal immune response increasing the production of pro-inflammatory c ytokines[10,18]
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