Dietary iron overload exacerbates intestinal damage induced by Eimeria tenella infection in broilers via impaired barrier integrity and gut microbiota dysbiosis.

Abstract

This study aims to investigate the effect of iron overload on intestinal damage in broilers infected with Eimeria tenella. A total of 240 one-day-old white-feathered broilers (Arbor Acres, AA) were randomly assigned to four groups based on a 2 &#xd7; 2 factorial design (2 dietary iron levels: 80 or 500 mg/kg; Eimeria tenella challenge: with or without), with six replicates per group, 10 birds per replicates. The dietary treatments were: 1) control group (CON) and attack group (AG): basal diet + 80 mg/kg FeSO. 2) high iron group (HF) and high iron + attack group (HFA): basal diet + 500 mg/kg FeSO. On day 18, broilers in the AG and HFA groups were challenged with 8 &#xd7; 10sporulated oocysts of Eimeria tenella, while broilers in CON and HF groups received Phosphate Buffered Saline (PBS). Our results indicates that: 1) Compared to the others, HFA had the lowest survival rate and the highest Eimeria fecal oocysts (P < 0.001) and showed lower expression of intestinal tight junction proteins (ZO-1, Claudin-1, and Occludin) in broilers (P < 0.05). 2) The interaction between these factors indicated that iron overload exacerbated the expression of IL-8 (P < 0.001) and IL-1&#x3b2; (P = 0.025) on 4 dpi, IL-1&#x3b2; (P = 0.023) on 8 dpi. 3) Both the Eimeria tenella challenge and the high-iron diet led to a significant increase in serum levels of DAO and LPS, while simultaneously decreasing the levels of IgA, IgG, and IgM (P < 0.05). 4) WGCNA-GSEA analysis revealed that the calcium signaling pathway, Wnt signaling pathway, and MAPK signaling pathway were specifically upregulated in HFA, while the TCA-cycle and fatty acid metabolism and degradation pathways were specifically downregulated. 5) Both the high-iron diet and Eimeria tenella challenge significantly altered the &#x3b1;-diversity and &#x3b2;-diversity of cecal microbiota (P < 0.05). Moreover, they significantly enriched microbial functions related to vancomycin resistance (ko01502), peptidoglycan biosynthesis (ko00550), and galactose metabolism (ko00052). In conclusion, this study indicates that iron overload exacerbates intestinal damage in broilers challenged by Eimeria tenella, potentially through its influence on the calcium signaling pathway in cecal tissue and altering both the structure and function of the cecal microbiota. An appropriate reduction in iron levels in poultry diets may contribute to enhanced coccidiosis control within the poultry industry.