Dietary exposure to lambda-cyhalothrin induces intestinal damage in chickens via oxidative stress and gut microbiota dysbiosis.

Lambda-cyhalothrin (LCT), a widely used pyrethroid insecticide for ectoparasite control in poultry and sanitation pest management, poses health risks to humans and animals despite its broad application. While LCT's intestinal toxicity has been underexplored, this study innovatively highlights dose-dependent differences in its effects through a novel chicken exposure model. Employing histological analysis, gene expression profiling, oxidative stress assays, and 16S rRNA sequencing, we systematically assessed varying LCT doses on chicken intestines. Results demonstrated pronounced dose-dependent impacts on the jejunum: LCT caused irregular, shortened, fractured, and fused villi; reduced goblet cells; induced inflammation; and downregulated barrier genes (Occludin, Claudin-1, Zonula Occludens-1 (ZO-1)). Notably, low-dose LCT activated the antioxidant system without significant oxidative stress, enabling partial mitigation of damage through adaptive responses. In contrast, high-dose LCT elevated reactive oxygen species, disrupted antioxidant balance, altered gut microbiota structure, decreased the Firmicutes/Bacteroidetes ratio, and reduced microbial richness, leading to severe dysbiosis and intestinal injury. This first comprehensive evaluation of LCT's dose-specific mechanisms-revealing adaptive resilience at low doses versus profound disruption at high doses-provides critical insights for safer pyrethroid use and mitigating poultry health risks.