59Fe Is Retained from an Elemental 59Fe Powder Supplement without Effects on 65Zinc, 47Calcium and 67Copper in Young Pigs

In vivo counting with the use of a germanium detector evaluated the retention of an elemental 59 Fe powder supplement while measuring potential interactions with zinc, calcium and copper. Effects of dietary iron and zinc on in vivo retentions of 59 Fe, 65 Zn, 67 Cu and 47 Ca were studied in young pigs. In Experiment 1, 4-d-old piglets fed a cereal-based diet were randomly assigned to one of four treatment groups (2 x 2 factorial arrangement, n = 5 per group). Variables were dietary iron source (either elemental iron or FeSO 4 , each at 100 mg iron/kg diet) and the dosage form of radioactive iron (either elemental 59 Fe powder or 59 FeSO 4 ). Experiment 2 (2 x 3 factorial arrangement) was performed using two levels of iron (100 and 200 mg/kg, as elemental iron) and three levels of zinc (25, 50 and 100 mg/kg). Piglets were also dosed with 47 Ca, 65 Zn and 67 Cu; all radioisotopes were measured for 8 d. Apparent absorption of elemental 59 Fe powder was 13 ± 1%, whereas 59 Fe sulfate was significantly (P < 0.05) higher at 26 ± 1%. The FeSO 4 diet decreased 65 Zn retention in Experiment 1, in contrast to the elemental iron diet, which did not have this effect in either experiment. Apparent 65 Zn absorption averaged 44 ± 2, 35 ± 1 and 27 ± 2% for the three levels of zinc (25, 50 and 100 mg/kg), respectively. Retention of 47 Ca was not affected by dietary iron or zinc; retention of 67 Cu was not affected by dietary iron. The data demonstrate good bioavailability of elemental iron without effects on zinc, copper and calcium.