Phytogenic supplementation mitigates necrotic enteritis in broilers through modulation of gut microbiota, short-chain...

With the withdrawal of antibiotic growth promoters, phytogenic compounds have gained attention as potential alternatives for enhancing gut health and modulating the intestinal microbiota. This study investigated the effects of a phytogenic blend (PHB) containing thymol, oleic acid, capric acid, and refined sunflower fat on cecal short-chain fatty acids (SCFA), jejunal gene expression, and cecal microbiota composition in broiler chickens under necrotic enteritis (NE) challenge. A total of 450 d-old mixed-sex Cobb 500 broiler chicks were randomly allocated to three treatments: non-challenged control without additives (NC), NE-challenged control without additives (CC), and NE-challenged supplemented with 0.01% phytogenic blend (PHB). Birds in challenge groups were orally inoculated with Eimeria spp. on d9 and Clostridium perfringens on d14 to induce NE. Data were analyzed using one-way ANOVA, and mean separation was performed by Tukey's test (P < 0.05). Microbiota composition was assessed through 16S rRNA sequencing, and downstream microbiome analyses and visualization were performed using R version 4.6.1 (R Core Team, 2026) in RStudio. The NE challenge upregulated interferon-gamma (IFN-γ; P < 0.05), downregulated claudin 5 (CLDN5; P < 0.05) and immunoglobulin M (IgM; P < 0.05) genes, and significantly increased iso-butyric, iso-valeric, and valeric acid concentrations compared to the NC group (P < 0.05). Moreover, it reduced microbial diversity (P < 0.05) and increased the abundance of potentially pathogenic genera, including Clostridium sensu stricto 1, and Escherichia Shigella. The dietary PHB significantly reduced the concentrations of iso-butyric, iso-valeric, and valeric acids, and increased lactic and succinic acids (P < 0.05), and upregulated APN (P < 0.05). l-type amino acid transporter 1 (LAT1) showed an intermediate response in the PHB group and did not reach statistical significance compared to CC (P > 0.05). Furthermore, PHB did not significantly affect IFN-γ, CLDN5, or IgM levels (P > 0.05). Microbiota analysis revealed distinct β-diversity clustering between CC and PHB groups and increased abundance of beneficial bacterial taxa in the PHB group, including Tyzzerella, Lactobacillus, Anaerostipes, Ruminococcus_torques_group, Butyricicoccus pullicaecorum, with an elevated Firmicutes-to-Bacteroidetes ratio. These findings suggest that PHB supplementation alleviated NE-induced gut dysbiosis and metabolic disruption by promoting beneficial bacteria, improving SCFA profiles, and enhancing mucosal gene expression related to digestion.