Dietary supplementation of ferrous glycinate improves intestinal barrier function by modulating microbiota composition in Cherry Valley ducks

Ferrous glycinate (Fe-Gly) has been increasingly used as iron fortification in the diets of weaned piglets and broilers, but the effect of Fe-Gly on intestinal barrier function in meat ducks has not been well defined. This study therefore investigated the effect of Fe-Gly on apparent nutrient utilization, hematological indices, intestinal morphological parameters, intestinal barrier function and microbial composition in meat ducks. A total of 672 one-day-old Cherry Valley ducks were randomly divided into 6 treatments (8 replicates for each treatment and 14 ducks for each replicate) and fed diets with 0 (control), 30, 60, 90 and 120 mg/kg Fe-Gly or 120 mg/kg FeSO(4) for 35 d. The results showed that diets supplemented with Fe-Gly significantly increased average daily gain (ADG), average daily feed intake (ADFI), hematocrit (HCT), mean cell volume (MCV), the apparent utilization of dry matter (DM) and metabolizable energy (ME), villus height (VH) and villus height-to-crypt depth ratio (V:C) (P < 0.05). Fe-Gly also significantly up-regulated barrier-related genes including zonula occludens-1 (ZO-1), zonula occludens-2 (ZO-2), mucin 2 (MUC2) and lysozyme (LYZ) (P < 0.05), and down-regulated the mRNA expression of claudin-2 (CLDN2) and occludin (OCLN) in the jejunum (P < 0.05). The 16S rRNA sequence analysis indicated that the diet with Fe-Gly had a higher relative abundance of Intestinimonas and Romboutsia (P < 0.05), which have an ability to produce short chain fatty acids (SCFAs), especially butyric acid. It also decreased the relative abundance of pathobiont, including Megamonas, Eubacterium_coprostanoligenes_group and Plebeius (P < 0.05). Additionally, diets supplemented with 120 mg/kg Fe-Gly significantly increased the apparent utilization of DM and ME (P < 0.05) and decreased the relative abundance of Megamonas_unclassified and Bacteroides_unclassified compared with those fed 120 mg/kg FeSO(4) (P < 0.05). These results revealed that diets supplemented with Fe-Gly exerted a potent beneficial effect on physical, chemical, immune and microbial barriers, thereby improving the integrity of the intestinal structure, promoting the digestion and absorption of nutrients to a certain extent, and ultimately elevating the growth performance of ducks.