Iron bioavailability from hemoglobin and hemin in chick, rat, cat, and dog: A comparative study

Experiments were conducted, using hemoglobin concentration, hematocrit and total body gain in hemoglobin, to assess iron bioavailability from dietary hemoglobin and hemin across several species. Iron bioavailability was determined by adding hemoglobin and hemin to casein-dextrose basal diets to provide iron within the linear response range for each species. Similar diets were fed to all species with the exception that the cat diet contained 25% poultry fat to improve acceptability and growth whereas 3% corn oil was used in chick, rat, and dog diets. Percent bioavailability relative to ferrous sulfate-iron was calculated using standard curve methodology in chick, cat, and dog assays, and slope-ratio methodology in the rat assay. In species that were less homogeneous in size, i.e., cats and dogs, both initial and final body weights varied considerably, therefore estimates based on total body gain in hemoglobin were deemed to be more accurate estimates of iron bioavailability. Hemin was poorly available to rats but completely unavailable to chicks, cats and dogs. Hemoglobin iron bioavailability was 68% for rats, 93% for chicks, 90% for dogs, and 70% for cats. The protein portion of the hemoglobin molecule is hypothesized to play a critical role in heme iron absorption from a casein dextrose based diet in these species. (C) 2000 Elsevier Science Inc.