Gut-Derived Lactobacillus rhamnosus GG Alleviates Intestinal Inflammation in Laying Hens via Microbiota Remodeling and Tryptophan Metabolic Reprogramming

Intestinal inflammation compromises nutrient absorption, health, and productivity in laying hens. Here, we isolated a gut-resident Lactobacillus rhamnosus GG (LGG) strain from indigenous chickens and evaluated its prophylactic effects against dextran sulfate sodium (DSS)-induced intestinal inflammation. Oral LGG administration improved growth performance and antioxidant capacity, restored the villus structure, and reinforced epithelial barrier integrity by upregulating tight junction genes. LGG markedly reduced pro-inflammatory cytokines ( IL -1β, IFN -γ) and increased TGF -β. 16S rRNA sequencing showed that LGG normalized microbial diversity, corrected the Firmicutes/Bacteroidetes ratio, enriched beneficial taxa ( Lactobacillus, Lachnoclostridium ), and reduced inflammation-associated genera ( Escherichia, Bacteroides ). Untargeted metabolomics revealed a significant modulation of tryptophan metabolism, including elevated levels of kynurenic acid, xanthurenic acid, and indoleglyoxylic acid. The microbiota–metabolite correlations indicate a coordinated regulatory axis underlying LGG-mediated protection. These findings demonstrate that native LGG mitigates intestinal inflammation through microbiota remodeling and metabolic reprogramming, supporting its potential as an antibiotic-free strategy for improving gut health in poultry.