Estimation of the relative bioavailability of zinc sources for broiler chicks.

University of Missouri, Columbia, Missouri, USA and Institute for Technology of Nuclear and Other Mineral Raw Materials, Serbia. *Corresponding author: ledouxd@missouri.edu An experiment was conducted with 260 day-old male broiler chicks to estimate the biological availability of three sources of Zn, two Zn-montmorillonites (Zn-MONT-A and Zn-MONT-B) and MINTREXZn. Zinc sulfate (ZnSO4) was used as the standard in the bioavailability assay. Chicks were allotted randomly to dietary treatments that included an un-supplemented corn-soybean meal basal diet (32 mg/kg Zn), or the basal diet supplemented with 10, 20 or 30 mg/kg Zn as either ZnSO4 (40.5% Zn), Zn-MONTA (1.3% Zn), Zn-MONT-B (1.85% Zn) or MINTREXZn (10% Zn). Dietary Zn level or source had no effect (P>0.05) on feed intake or body weight gain of chicks, which averaged 986 g and 801 g, respectively. Using the slope-ratio technique from the regression of tibia and toe Zn concentration on supplemental dietary Zn, and with Zn from ZnSO4 set at 100%, the relative biological availability values using tibia Zn were estimated to be 73, 118, and 132% for Zn-MONT-A, Zn-MONT-B, and MINTREXZn, respectively. For toe Zn, the bioavailability values were 88, 101, and 111% for ZnMONT-A, Zn-MONT-B, and MINTREXZn, respectively. Data suggest that both modified MONTs provided a source of bioavailable Zn, but Zn from MINTREXZn was more available to broiler chicks than Zn from Zn-MONT-A.