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.