Stamina Plus has spend 30 years studying the upper and lower levels, quality, bio-availability and sources of the required Trace Minerals needed for horses. This research has shown the levels needed and correct ratios to each other of these Trace Minerals. There are inorganic trace minerals that are used in the industry, but bio-availability varies by which source they come from. Stamina only uses inorganic trace minerals that we know the bio-availability of those trace minerals. The second source of trace minerals is organic and again their are different sources. Stamina Plus, in their products, uses a blend of inorganic and organic trace minerals, with the correct ratios and bio-availability for the best nutrition for your horse.