Micromineral Requirements in Horses

Minerals required in minute amounts by horses are specified as microminerals. These nutrients play an important role in a wide range of biochemical systems which affect virtually every metabolic function in the horse. With the exception of selenium, little attention has been given to microminerals in horse nutrition until shortly before the publication of the current NRC Nutrient Requirements of Horses in 1989. Since then, a great deal of research has been directed towards microminerals, particularly as they affect skeletal development in growing horses. Still, many questions remain unanswered about specific requirements for microminerals in many classes of horses. This paper will briefly review the principal functions of copper, chromium, iodine, iron, manganese, selenium and zinc and will highlight recent research that has been conducted with each micromineral in horses. It will also attempt to combine these data with practical experience to provide recommendations for inclusion of these minerals in horse rations.