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 6treatments(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 Fe SO4for 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). FeGly 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 m RNA expression of claudin-2(CLDN2) and occludin(OCLN) in the jejunum(P < 0.05). The 16S r RNA 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 fed120 mg/kg Fe SO4(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.