Cinnamaldehyde Alleviates Salmonellosis in Chicks by Regulating Gut Health.

Due to the high mortality rate in chicks caused by pullorum disease (PD) and the drawbacks of antibiotic resistance, the poultry industry is increasingly interested in using natural herbal antimicrobial agents as alternatives, with cinnamaldehyde (CA) being a focus due to its multitarget and synergistic effects. This study aimed to evaluate the effects of oral administration of CA on restoring intestinal physical integrity, intestinal microbial barrier, and intestinal metabolism in a laboratory model of () infection in chicks. Thirty-six chicks were divided into six groups. The S.P and CA groups were infected with 5 × 10 CFU/mL, 0.5 mL , while the CON group received an equal-volume saline injection. The CA group was treated with 100 mg/kg CA, and the others received phosphate buffer saline (PBS). Samples were collected 24 h after the last treatment. Intestinal physical integrity was assessed by H&E staining, and ELISA was used to measure inflammatory factors. In situ hybridization (ISH) and RT-qPCR were used to measure the expression of tight-junction protein mRNA. The microbiota was analyzed by 16S rRNA gene sequencing of the ileal contents, and metabolite analysis was performed on the intestinal contents. After CA treatment, the expression of IL-1β and TNF-α was reduced, and IL-10 was increased ( < 0.05). H&E staining showed that the intestinal structure was partially restored after treatment. ISH results showed that the fluorescence intensity indicating gene expression status was low in the S.P group and high in the CA group, indicating reduced intestinal permeability. RT-qPCR showed that CA up-regulated the mRNA expression of tight-junction proteins (claudin-1, occludin-1, and zo-1, < 0.05). The 16S rRNA gene sequence analysis showed that was significantly enriched in the S.P group (LDA score > 2.0, < 0.05), while specific genera were significantly more abundant in the treated groups. Untargeted sequencing of intestinal contents showed that key metabolites (butyrate, alanine, glutamate, cholesterol, and propionate) in the CA group were significantly changed compared with the S.P group ( < 0.05). CA treatment was the most effective method for reducing PD intestinal colonization and maintaining better intestinal homeostasis, possibly by regulating intestinal microbiota and metabolic functions.