BIOAVAILABILITY OF IRON IN COTTONSEED MEAL, FERRIC SULFATE, AND 2 FERROUS SULFATE BY-PRODUCTS OF THE GALVANIZING INDUSTRY

Iron depletion-repletion assays were carried out with young chicks to establish Fe bioavailability values for Fe-2(SO4)(3). 7H(2)O (22.7% Fe ), Fe-ZnSO4. H2O (20.2% Fe, 13.0% Zn), Zn-FeSO4. H2O (20.2% Zn, 14.2% Fe), and cottonseed meal (200 mg Fe/kg). Standard hemoglobin response curves were established using feed-grade FeSO4. H2O (28.8% Fe) or reag ent-grade FeS(O)4 . 7H(2)O (20.1% Fe) as standards such that relative bioavailability (RBV) could be assessed for the experimental sources o f Fe. Weight gain, hemoglobin, and hematocrit responded linearly (P < 0.05) to Fe supplementation in all assays. Using hemoglobin as the res ponse criterion, slope-ratio calculations established Fe REV values of 126% for Fe-ZnSO4. H2O and 93% for Zn-FeSO4. H2O The 126% value for F e-ZnSO4. H2O was greater (P < 0.05) than the FeSO4. H2O standard (100% ), but the 93% value for Zn-FeSO4. H2O was not different (P > 0.10) fr om the standard. However, evaluation of all criteria of response (hemo globin, hematocrit, weight gain) suggested that neither Fe-ZnSO4H2O no r Zn-FeSO4. H2O had different Fe REV values than FeSO4. H2O Standard-c urve calculations were used for assessment of Fe REV in Fe-2(SO4)(3). 7H(2)O and cottonseed meal, as only a single level of Fe addition was studied for each of these products. Iron REV in Fe-2(SO4)(3). 7H(2)O w as estimated to be 37%, whereas Fe REV in cottonseed meal was found to be 56%. Both of these values were lower (P < 0.05) than the FeSO4 sta ndard. The data suggest that the two new products, representing combin ations of FeSO4. H2O and ZnSO4. H2O by-products of the galvanizing ind ustry, are excellent sources of bioavailable Fe, whereas ferric sulfat e and cottonseed meal are relatively poor sources of usable Fe.