Zinc-loaded montmorillonite alleviates avian pathogenic <i>Escherichia coli</i> -induced intestinal barrier damage in broiler chickens

Avian pathogenic Escherichia coli (APEC) significantly compromises the intestinal barrier of broiler chickens. This study evaluated the protective effects of zinc-loaded montmorillonite (Zn-MMT), an inorganic antibacterial compound, against APEC challenge in broiler chickens. A total of 180 1-d-old male Arbor Acres broilers were randomly divided into 3 groups with 6 replicates of 10 birds each. The treatment groups were: 1) the control group (basal diet); 2) the APEC-challenged group (basal diet); and 3) the Zn-MMT-supplemented group (basal diet + 1,000 mg/kg Zn-MMT). On day 14, groups 2 and 3 were orally challenged with APEC, while controls received sterile broth. Intergroup differences were assessed using one-way ANOVA and Tukey's multiple comparison test. Compared with the APEC-challenged group, dietary Zn-MMT supplementation reduced myeloperoxidase activity in both jejunal and ileal mucosa and increased the relative weight of the small intestine (duodenum, jejunum, and ileum) (P < 0.05). Moreover, Zn-MMT lowered serum endotoxin and D-lactate concentrations, as well as diamine oxidase activity, while increasing jejunal villus height and the ratio between villus height and crypt depth (P < 0.05). The incorporation of Zn-MMT upregulated the expression of jejunal zonula occludens-1 and claudin-1 and ileal zonula occludens-1 (P < 0.05). Additionally, Zn-MMT decreased the apoptosis rates of the epithelial cells in the jejunum and ileum (P < 0.05). The Zn-MMT supplementation restored the expression of cysteine-requiring aspartate protease-3, cysteine-requiring aspartate protease-9, B cell lymphoma-2, and tumor protein 53 in the jejunum and/or ileum of the APEC-challenged chickens (P < 0.05). Dietary supplementation with Zn-MMT improved antioxidant capacity of APEC-challenged chickens by increasing the activities of superoxide dismutase and catalase, elevating reduced glutathione levels, and inhibiting the accumulation of malondialdehyde in serum and/or intestinal mucosa (P < 0.05). The results suggested that Zn-MMT was effective in alleviating intestinal barrier damage in APEC-challenged broiler chickens by alleviating inflammation, reducing intestinal permeability, regulating tight junction protein expression, preventing intestinal apoptosis, modulating apoptosis-related genes, and mitigating oxidative stress.