Methodology for assessing zinc bioavailability: efficacy estimates for zinc-methionine, zinc sulfate, and zinc oxide.
The bioavailability of zinc-methionine (ZnMET) was compared to that of feed-grade ZnSO4.H2O using three different diets: purified (crystalline amino acid [AA]), semipurified (soy isolate), and complex (corn-soybean [C-SBM]) diet. With the Zn-deficient purified or semipurified diet, weight gain and tibia Zn responded linearly to both ZnSO4.H2O and ZnMET supplementation. Common-intercept, multiple linear regression indicated differences in Zn bioavailability between ZnMET and ZnSO4.H2O for both diets as indicated by bone Zn. With the ZnSO4.H2O standard set at 100%, bioavailability of Zn from ZnMET was 117% (P less than .05) in the AA diet and 177% (P less than .01) in the soy isolate diet. The ZnMET was also compared to ZnSO4.H2O in a C-SBM diet containing 117 mg of Zn/kg. When high levels of Zn were added to this diet (0, 250, 500, and 750 mg/kg of supplemental Zn), consistent tissue Zn responses did not occur beyond the first increment. Addition of lower levels of supplemental Zn (0, 5, 10, 20, 30, 40 and 50 mg/kg) to a Zn-unsupplemented C-SBM basal diet (45 mg/kg of Zn), however, resulted in a broken-line, two-slope response in tibia Zn for both ZnMET and ZnSO4.H2O. Inflection points occurred at 60 and 54 mg of Zn/kg of diet for ZnSO4.H2O and ZnMET, respectively. The ratio of slopes (ZnMET:ZnSO4.H2O) below the inflection points was 206% (P less than .01), indicating that Zn was considerably more bioavailable in ZnMET than in ZnSO4.H2O for chicks consuming C-SBM diets. When feed-grade ZnO was compared to feed-grade ZnSO4.H2O in chicks consuming C-SBM diets, bone Zn slopes below the respective inflection points indicated that Zn was 61% bioavailable in ZnO relative to ZnSO4.H2O.
Wedekind
K J
KJ
Department of Animal Science, University of Illinois, Urbana 61801.
Hortin
A E
AE
Baker
D H
DH
D000821:Animal Feed; D000818:Animals; D001682:Biological Availability; D002645:Chickens / Q000378:metabolism*; D005527:Food, Fortified; D008297:Male; D008715:Methionine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D009942:Organometallic Compounds / Q000493:pharmacokinetics*; D012044:Regression Analysis; D013431:Sulfates / Q000493:pharmacokinetics* / Q000494:pharmacology; D013977:Tibia / Q000737:chemistry; D015430:Weight Gain / Q000187:drug effects; D015032:Zinc / Q000032:analysis / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D015034:Zinc Oxide / Q000493:pharmacokinetics* / Q000494:pharmacology; D019287:Zinc Sulfate
D009942:Organometallic Compounds; D013431:Sulfates; C074508:zinc methionine; D019287:Zinc Sulfate; D008715:Methionine; D015032:Zinc; D015034:Zinc Oxide