The chemical characteristics of different sodium iron ethylenediaminetetraacetate sources and their relative bioavailabilities for broilers fed a conventional corn-soybean meal diet

Abstract

Background Our previous studies demonstrated that divalent organic iron (Fe) proteinate sources with higher complexation or chelation strengths as expressed by the greater quotient of formation (Qf) values displayed higher Fe bioavailabilities for broilers. Sodium iron ethylenediaminetetraacetate (NaFeEDTA) is a trivalent organic Fe source with the strongest chelating ligand EDTA. However, no study on the bioavailability of Fe as NaFeEDTA in broilers and other agricultural animals has been reported before. Herein, firstly, 12 NaFeEDTA products were collected, and their chemical characteristics were determined. And then, one feed grade NaFeEDTA (Qf value = 2.07 × 108), one food grade NaFeEDTA (Qf value = 3.31 × 108) and one Fe proteinate with an extremely strong chelation strength (Fe-Prot ES, Qf value = 8,590) were selected to evaluate their bioavailabilities relative to Fe sulfate (FeSO4·7H2O) for broilers fed a conventional corn–soybean meal diet during d 1 to 21 by investigating the effects of the above Fe source and added Fe level on the growth performance, hematological indices, Fe contents, activities and gene expressions of Fe-containing enzymes in various tissues of broilers. Results NaFeEDTA sources varied greatly in chemical characteristics. Plasma Fe concentration (PI), transferrin saturation (TS), liver Fe content, succinate dehydrogenase (SDH) activities in liver, heart and kidney, catalase (CAT) activity in liver, and SDH mRNA expressions in liver and kidney increased linearly (P < 0.05) as supplemental Fe levels increased. However, differences among Fe sources were detected (P < 0.05) only for PI, liver Fe content, CAT activity in liver, SDH activities in heart and kidney, and SDH mRNA expressions in liver and kidney. Based on slope ratios from multiple linear regressions of the above indices on daily dietary analyzed Fe intake, the average bioavailabilities of Fe-Prot ES, feed grade NaFeEDTA, and food grade NaFeEDTA relative to the inorganic FeSO4·7H2O (100%) for broilers were 139%, 155%, and 166%, respectively. Conclusions The relative bioavailabilities of organic Fe sources were closely related to their Qf values, and NaFeEDTA sources with higher Qf values showed higher Fe bioavailabilities for broilers fed a conventional corn-soybean meal diet.