Bioavailability of supplemental trace elements for domestic animals

The bioavailability of the various sources of the trace elements must be known to make effective use of commercial products. In general, the soluble forms of the microminerals including the sulfates and chlorides are well utilized by animals. The carbonate and oxide forms tend to be less well utilized, but this varies with element. Sodium selenite and sodium selenate, the only forms of selenium approved for supplemental use in the United States, are both well utilized. Biologically available forms of iodine include sodium or potassium iodide, calcium iodate, pentacalcium orthoperiodate, and ethylenediamine dihydriodide. The organic complexes have been demonstrated to be equal to or, in some studies, somewhat greater in bioavailability than the same element in the sulfate or chloride form. In studies where identical products were tested, the relative bioavailability estimates appear to be similar whether tested with nonruminants (chicks) or with ruminants (lambs).