Environmental fluoride exposure disrupts the intestinal structure and gut microbiota alteration in duck

Fluoride (F) and its compounds produced from industrial production and coal combustion can cause air, water and soil contamination, which also accumulate in animals and plants and threaten human health through the food chain. Fluoride exposure has been known to cause adverse effects on the liver, kidney, reproductive system and gastrointestinal diseases, but studies regarding fluoride influence on intestine and gut microbiota in waterfowl have been insufficient to date. Here, this study was performed to investigate fluoride’s effects on the intestinal mechanical barrier and microbial community in ducks. Results indicated that excessive fluoride impaired the structure of intestinal tissue and reduced the relative distribution of goblet cells involved in defense response. Moreover, the gut bacterial community in F compound exposed ducks displayed a significant decrease in alpha diversity, accompanied by distinct alterations in taxonomic compositions. Proteobacteria, Firmicutes and Bacteroidetes were the most preponderant phyla in all the samples. At the level of genus, the differences in richness and diversity between control and fluoride-induced populations were gradually observed. Specifically, fluoride induction resulted in a significant decrease in the relative abundance of 9 bacterial phyla and 15 bacterial genera. Among them, 4 phyla (Latescibacteria, Dependentiae, Zixibacteria and Fibrobacteres) and 4 genera (Thauera, Hydrogenophaga, Reyranella and Arenimonas) even cannot be detected in the gut microbiota of ducks treated with fluoride compounds. In summary, this study demonstrated that excessive fluoride intake could significantly damage the intestinal barrier and alter the gut microbiota diversity and composition in ducks. Remarkably, it is the first insight about fluoride on gut microbiota of ducks.