Metabolic utilization of intravenously injected iron from different iron sources in target tissues of broiler chickens

No information is available regarding the utilization of iron (Fe) from different Fe sources at a target tissue level. To detect differences in Fe metabolic utilization among Fe sources, the effect of intravenously injected Fe on growth performance, hematological indices, tissue Fe concentrations and Fe-containing enzyme activities and gene expressions of Fe-containing enzymes or protein in broilers was investigated. On d 22 post-hatching, a total of 432 male chickens were randomly allotted to 1 of 9 treatments in a completely randomized design. Chickens were injected with either a 0.9% (wt/vol) NaCl solution (control) or a 0.9% NaCl solution supplemented with Fe sulphate or 1 of 3 organic Fe sources. The 3 organic Fe sources were Fe chelates with weak (Fe-MetW), moderate (Fe-ProtM) or extremely strong (Fe-ProtES) chelation strength. The 2 Fe dosages were calculated according to the Fe absorbabilities of 10% and 20% every 2 d for a duration of 20 d. Iron injection did not affect (P > 0.05) ADFI, ADG or FCR during either 1 to 10 d or 11 to 20 d after injections. Hematocrit and Fe concentrations in the liver and kidney on d 10 after Fe injections, and Fe concentrations in the liver or pancreas and ferritin heavy-chain (FTH1) protein expression level in the liver or spleen on d 20 after Fe injections increased (P ≤ 0.05) as injected Fe dosages increased. When the injected Fe level was high at 20% Fe absorbability, the chickens injected with Fe-ProtES had lower (P < 0.001) liver or kidney Fe concentrations and spleen FTH1 protein levels than those injected with Fe-MetW or Fe-ProtM on d 20 after injections. And they had lower (P < 0.05) liver cytochrome C oxidase mRNA levels on d 20 after injections than those injected with Fe-MetW or Fe sulphate. The results from this study indicate that intravenously injected Fe from Fe-ProtES was the least utilizable and functioned in the sensitive target tissue less effectively than Fe from Fe sulfate, Fe-MetW or Fe-ProtM.