Effect of iron source on iron absorption by in situ ligated intestinal loops of broilers

Two experiments were conducted to investigate the effect of iron (Fe) source on Fe absorption by in situ ligated intestinal loops of broilers. In Experiment 1, in situ ligated intestinal loops from Fe-deficient chicks (29 days old) were perfused with solutions containing 0.45 mmol Fe/L from FeSO4 (FeSO4 center dot 7H(2)O), Fe-Gly chelate, Fe-Met chelate, one of three Fe-amino acid or protein complexes with weak, moderate or extremely strong complex strength (Fe-Met W, Fe-Pro M, or Fe-Pro ES), or the mixtures of FeSO4 with either Gly or Met (Fe + Gly or Fe + Met), respectively, up to 30 min. In Experiment 2, in situ ligated duodenal loops from Fe-deficient chicks (29 days old) were perfused with solutions containing 0-3.58 mmol Fe/L from FeSO4, Fe-Met W, Fe-Pro M, or Fe-Pro ES up to 30 min. The absorptions of Fe from both inorganic and organic Fe sources in the ligated duodenum were similar to 1.35-2.8 times higher (P < 0.05) than that in the ligated jejunum or ileum. The absorption of Fe as Fe-ProMor Fe-Pro ES was higher (P < 0.05) than that of Fe as inorganic Fe or Fe-MetWat Fe concentration of 3.58 mmol/L. The absorption kinetics of Fe from organic and inorganic Fe sources in the ligated duodenal loops followed a saturable process as determined by regression analysis of concentration-dependent absorption rates. The maximum absorption rate and Michaelis-Menten constant values in the ligated duodenal loops were higher (P < 0.05) for Fe-Pro M and Fe-Pro ES than for FeSO4 and Fe-Met W. The results from this study indicate that the duodenum was the main site of Fe absorption in the intestines of broilers; organic Fe sources with stronger complex strength values showed higher Fe absorptions at a higher concentration of added Fe; and the simple mixture of FeSO4 with amino acids did not increase Fe absorption.