Gut microbial dysbiosis is associated with altered splenic immune homeostasis in chickens.

Gut microbiota plays a crucial role in animal health and immunity, and the broiler gut community is particularly sensitive during the early growing and finisher phases, when it is still maturing and immune development is active. In this study, we investigated the association between changes in the intestinal flora and splenic immune parameters in Qingyuan partridge chickens. A total of 40 twenty-week-old roosters were used. The results showed that antibiotic treatment (ABX) reduced the proportion (percentage) of splenic CD3+ T cells and increased the levels of inflammatory cytokines (IL-6, IL-1β, and TNF-α). Antibiotic treatment also reduced α- and β-diversity of the gut microbiota. Transcriptomic analysis identified 145 differentially expressed genes (DEGs, |log2FoldChange| > 1, Benjamini-Hochberg-adjusted P < 0.05) in the spleen, including CCR9, OPCML, and HEBP1, enriched in neuroactive ligand-receptor interaction, phagosome, and lysosome pathways. Antibiotic treatment reduced the relative abundance of Verrucomicrobiota and Actinobacteriota at the phylum level. At the genus level, Wilcoxon analysis showed Ligilactobacillus was reduced in ABX (P = 0.031), although LEfSe flagged it as ABX-enriched owing to a single high-abundance outlier. Microbacterium was consistently enriched in ABX. Correlation analysis revealed that Actinobacteriota and the genera Ligilactobacillus and Aeriscardovia were positively associated with CD3+ T-cell proportions. In summary, changes in gut microbiota were associated with altered splenic immune parameters in chickens.