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Effects of early-life cecal microbiota transplantation on aggressive behavior and health in roosters
Recent studies have revealed that fecal microbiota transplantation exerts beneficial effects on modulating stress-related inflammation and behavioral disorders in mammals. The aim of this study was to examine if cecal microbiota transplantation (CMT) presents similar efficiency in improving the health status and reducing aggression in egg-laying strain roosters. Cecal contents were collected from the divergently selected 63 (gentle) and 72 (aggressive) chicken lines based on resistance or susceptibility to Marek’s disease, resulting in line’s unique physiological and behavioral characteristics. Eighty-four 1-d-old male chicks of Dekalb XL strain were randomly assigned into 3 treatments with 7 replicates per treatment of 4 birds per replicate: CTRL (0.1 ml of saline), 63-CMT (0.1 ml cecal solution of line 63), and 72-CMT (0.1 ml cecal solution of line 72) for a 16-wk trial. Cecal microbiota transplantation was conducted once daily from d 1 to d 10 and then boosted once weekly from wk 3 to wk 5. At wk 5, 11, and 16, body weight and blood samples were collected for detecting CMT-induced physiological changes of recipient birds. Samples of the spleen, ileum, hypothalamus, and cecal contents were collected at wk 5 and 16. Behavioral data was analyzed at the same time points. The results indicated that transplantation altered the structures and diversity of the gut microbial community in recipient birds, which led to differences in performance traits, neuroendocrine and immune systems, and exhibition of aggression. Compared to CTRL birds, 72-CMT birds had better nutrient digestion and absorption but lower stress adaptive capacity at wk 5, while 63-CMT birds had reduced systemic inflammation resulting from the up-regulation of anti-inflammatory cytokine IL-10, together with down-regulation of pro-inflammatory cytokines TNF-α and IL-6 at wk 16. In addition, CMT induced a lower frequency of aggression with a higher hypothalamic serotonergic activity in 63-CMT birds at wk 5. Meanwhile, genus Ruminococcaceae UCG-005 was found to be positively correlated with brain serotonin levels (P < 0.05) in 63-CMT birds, while genus GCA-900066225 was negatively correlated with 5-HIAA (P < 0.05) in 72-CMT birds at wk 5. Taken together, early postnatal CMT in recipient birds induces donor’s line-related effects on performance traits, stress adaptive capability, aggressive behavior, immune and neuroendocrine functions through regulating the gut-microbiota-brain and gut-microbiota-immune axes. The findings may provide new insights into developing management methods for controlling aggressive behavior in poultry.