Microbiota profiles and intestinal immunity in Bermuda feral chickens: A comparison with commercial broilers.

Domestication for production and captive rearing may alter the chicken gut microbiome and compromise immune function in modern broiler chickens. In this study, we compared microbiota, Toll-like receptor (TLR) gene expression, and intestinal health between feral chickens from Bermuda (BFC, n = 21) and commercial Cobb 500 broilers (BC, n = 12). Microbiota analysis showed that feral chickens harbored greater microbial diversity with higher proportions of Gram-negative bacteria in BFC (31%) vs. BC (8.2%). RT-qPCR analysis, followed by ANOVA and Tukey's test, revealed higher ileal expression of TLR in BFC and hepatic expression in BC (P < 0.05) indicating enhanced mucosal innate immunity in feral chickens and systemic immune activation in broiler chickens, respectively. The upregulation of ileal TLR4 and TLR5 in feral chickens correlated with Gram-negative and flagellated Proteobacteria, respectively. Histological evaluation showed higher Intestinal Scoring Index (ISI) scores in BFC (Kruskal-Wallis test, P < 0.05) with increased lamina propria thickness, goblet cell proliferation, and a robust mucosal inflammatory response, while BC showed minimal mucosal inflammation but significant hepatic lymphocytic aggregation and congestion (P < 0.05). These findings suggest that feralization and free-living conditions are associated with a high mucosal immune surveillance that effectively limits systemic antigen translocation, while commercial broilers show reduced intestinal immune activation and increased susceptibility to hepatic inflammation. This indicates that selection for intensive production may compromise gut barrier function and shift the site of immune activation from the mucosa to the liver.