Baicalin alleviates APEC-induced ileal barrier injury in broiler chickens by modulating inflammatory responses, microbiota composition, and neuro-immune-related transcriptional profiles

Abstract

Avian pathogenic Escherichia coli (APEC) can disrupt intestinal barrier integrity and induce mucosal inflammation in broiler chickens. Baicalin, a flavonoid derived from Scutellaria baicalensis , has anti-inflammatory and intestinal protective properties, but its effects on APEC-associated ileal injury and the accompanying microbial and host transcriptional responses remain incompletely understood. A total of 288 one-day-old broilers were assigned to four treatments: a basal diet with saline administration (BD+Saline), a basal diet with APEC challenge (BD+APEC), and basal diets supplemented with 150 (LB+APEC) or 300 mg/kg baicalin (HB+APEC) followed by APEC challenge. Birds were orally challenged with APEC O78 on d 18–20 and again on d 39–41, with samples collected on d 21 and d 42, respectively. Ileal morphology, goblet cell numbers, serum permeability-related markers, barrier-, inflammatory-, and Nrf2-related gene expression, ileal microbiota, and transcriptomic profiles were evaluated. APEC challenge impaired ileal morphology and reduced goblet cell numbers at both sampling ages, with increased serum DAO and LPS following the second challenge. Baicalin improved villus architecture, goblet cell abundance, tight junction-related gene expression, and inflammatory responses, and reduced serum DAO and LPS following the first challenge. It also attenuated APEC-associated upregulation of Nrf2-related antioxidant genes. Microbiota analysis showed increased Corynebacterium at both sampling ages and Weissella following the first challenge. Transcriptomic and qRT-PCR analyses highlighted NPY , NPY1R , AGTR1 , IL-10 , IFN-γ , and MYL10 as genes associated with neuro-immune-, cytokine-, and cytoskeleton-related responses. Dietary baicalin alleviated APEC-induced ileal barrier injury in broiler chickens by improving mucosal structure, goblet cell abundance, tight junction-related gene expression, and inflammatory responses. Baicalin also altered the ileal microbiota, including increased relative abundances of Corynebacterium and Weissella , and modified neuro-immune-related transcriptional responses involving NPY , NPY1R , AGTR1 , IL-10 , IFN-γ , and MYL10 . Collectively, these findings demonstrate the beneficial effects of dietary baicalin on intestinal barrier integrity, inflammation, and microbial and transcriptional responses during APEC challenge, supporting its potential as a plant-derived functional feed additive for improving intestinal health in broilers.