You might have noticed chelated minerals in the ingredients list of your horse’s feed or supplement, and wondered what they are and whether or not they are better than regular minerals.
Within the digesta (partially digested food travelling through the gut) minerals can take the form of either metallic ions in solution, as part of organic complexes in solution (including chelates) or as part of insoluble substances (which are not absorbed at all). The first two forms are absorbed. The most common form of minerals found in horse feeds and supplements are the inorganic form, such as magnesium oxide and zinc sulphate. Chelated minerals occur naturally in feeds, and laboratory-created chelated minerals are sometimes added to both supplements and horse feeds.
Chelated minerals are bound to an organic molecule, usually to protein or a subunit of protein such as an amino acid or peptide. The term ‘chelate’ is derived from the Greek word meaning ‘claw’. Chelated minerals are reputed to be more easily absorbed from the digestive tract, or more ‘bioavailable’ but there is little research to back this up.
Minerals are absorbed in the gut either by simple diffusion through the gut wall or by specialised transport. Exactly how each of the essential minerals is absorbed in the horses’ gut is not yet known. Mineral absorption rates are not constant but are affected by the amount in the diet, the amount the animal requires, the presence of other compounds in the digesta, the pH of the digesta, and the presence of different concentrations of other minerals in the digesta. For example, iron absorption increases when iron requirements are high, and calcium inhibits the absorption of zinc. Such complex interactions mean that calculating availability of different minerals from different sources is almost impossible. The sometimes-low bioavailability of minerals is taken into account in dietary requirements, so the idea that inorganic minerals are useless because they are not well absorbed shows misunderstanding.
The binding of minerals with organic molecules protects them from reactions with other compounds and in theory, could make them more bioavailable. Research, however, has failed to show consistent improvements in farm animal health or performance when chelated minerals replace inorganic minerals in the diet, and many question their extra cost.
Some research has been carried out on selenium-enriched yeast, compared to the inorganic sodium selenite commonly used in horse diets. One group of researchers showed that replacing a selenium salt with chelated selenium increased serum selenium levels in mares, and increased milk and colostrum selenium levels, but others showed no difference in 18 month old horses fed either sodium selenite or a selenium and methionine chelate.
Despite the belief that chelates are more bioavailable, there seems to be little difference in the use of chelates versus inorganic minerals in the horse’s diet.