• An infection model of Eimeria tenella in white-feathered broilers was established to evaluate the effects of two dietary iron levels (80 mg/kg and 500 mg/kg) on intestinal damage in broilers within this model. • Iron overload increased intestinal permeability and the expression of intestinal inflammatory factors and activated the intestinal calcium signaling pathway in broilers infected with Eimeria tenella. • Iron overload reduces the species diversity and richness of cecal microbiota, increases the abundance of pathogenic bacteria, and impairs the gut microbiota function. 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 × 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 4 . 2) high iron group (HF) and high iron + attack group (HFA): basal diet + 500 mg/kg FeSO 4 . On day 18, broilers in the AG and HFA groups were challenged with 8×10 4 sporulated 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-1β ( P = 0.025) on 4 dpi, IL-1β ( 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 α-diversity and β-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.
Guo et al. (Sun,) studied this question.