A MULTIELEMENT ISOTOPIC TRACER ASSESSMENT OF TRUE FRACTIONAL ABSORPTION OF MINERALS FROM FORMULA WITH ADDITIVES OF CALCIUM, PHOSPHORUS, ZINC, COPPER AND IRON IN YOUNG PIGLETS

True fractional absorption of minerals was measured to determine the bioavailability of Zn, Fe, Mn and Se from liquid formulas fortified with stepwise additions of Ca and P (as Ca glycerophosphate and carbonate, Ca*P), and Zn, Cu and Fe (as sulfate salts). Growth, deposition of tracers in organs and bone mineral content of femurs as assessed by single photon absorptiometry were measured. Four-day-old piglets (n = 36) were randomly assigned to groups fed a basal diet or additions of Ca*P (Ca = 25, P = 18 g/kg dry diet), Ca*P+Zn (Zn = 0.04 g/kg), Ca*P+Zn+Cu (Cu = 0.007 g/kg) or Ca*P+Zn+Cu+Fe (Fe = 0.008 g/kg). Oral and intravenous administration of extrinsic isotopes of Fe-59, Mn-54, Zn-65, Se-75 and Ca-47 was followed by fecal monitoring for 15 d and true absorption calculated after accounting for endogenous excretion. Addition of Ca*P+Zn reduced Zn absorption (P < 0.05) and Ca*P+Zn+Cu reduced Fe absorption (P < 0.01), but Mn and Se absorptions were not altered. Uptake of only Zn tracer into heart was significantly different (P < 0.05) among diet groups. Weight gain and linear growth were similar in all groups. Addition of Ca*P produced higher bone mineral density, but its effect on Zn absorption warrants further investigation.