Inorganic vs. Complexed Trace Minerals

Differences in trace mineral forms are well documented. These differences are represented in the degree of bioavailability of the specific trace mineral form. Bioavailability refers to the ability of trace minerals to be absorbed and metabolized in the animal. Oxide trace mineral forms are considered to have the lowest bioavailability, sulfate trace minerals have higher bioavailability, and complexed trace minerals are considered to have the highest bioavailability (17). The bioavailability of trace minerals fed to poultry is dependent not only upon the source of trace minerals but also upon amounts of other trace and macro minerals in the diet, as well as anti-nutritional factors such as phytate. Elements such as calcium, iron and sulfur can reduce the availability of other trace minerals. Some minerals compete for absorption or form insoluble compounds in the digestive system rendering the trace minerals unavailable to the animal. For example, the well-known affect of sulfur and molybdenum combining with copper to form tetrathiomolybdates in ruminants. Zinc and iron also decrease copper availability in livestock and poultry. Complexed trace minerals consistently show an increase in bioavailability over inorganic trace minerals (22, 23) through the ability of this form of trace minerals to avoid interaction with other trace minerals and dietary components in the digestive tract. As dietary antagonist level increases, the bioavailability of inorganic trace minerals diminishes relative to amino acid complexed minerals produced by Zinpro Corporation (Figure 1).

Attempting to increase trace mineral status of the animal by feeding higher levels of specific inorganic trace minerals may decrease the availability of other trace minerals in the diet, increase the toxicity risk, and increase excretion of those trace minerals into the environment. For example, high levels of copper or zinc can inhibit the absorption and utilization of the other trace mineral. Furthermore, trace mineral excretion is becoming a concern. Countries such as Japan and the European Union have passed legislation limiting dietary trace mineral levels. Interest has increased in the feeding of complexed trace minerals to improve trace mineral status, decrease mineral excretion and improve animal performance.

Figure 1.