Methods for estimating the bioavailability of supplemental trace elements

It is important to know the relative bioavailability of the essential micromineral elements in the various sources which can be obtained for use as dietary supplements for the production of livestock and poultry. Traditionally, such values have been estimated with dietary mineral concentrations below the animal's requirement. This paper has examined the use of tissue uptake of the micromineral following high-level, short-term supplementation as a measure for estimating mineral bioavailability. Except for seleno-amino acid compounds and certain iodine sources, this technique appears to have value in differentiating among commercial products with regard to their potential use as micromineral supplements. Where comparisons were made with the same sources, the rank order for utilization of manganese and copper compounds was similar for both poultry and sheep suggesting that information obtained with chicks may have value for use with ruminants as well.