Cobalt (Co), one of the microminerals, is important for blood cell formation.
The microbes in your horse's digestive system, particularly the cecum and large intestine, use the Co from your horse's diet to convert it to Vitamin B12. This vitamin is then used in conjunction with iron and copper in the formation and maintenance of blood cells.
The horse will usually consume enough Co through a typical diet.
All the common feedstuffs include at least 0.05 mg/kg dry matter, if not more (legumes usually contain around 0.6 mg/kg dry matter except in deficient areas).
The requirement has been set at 0.1 mg/kg dry matter, so this is easily reached through the typical diet.
Areas of New England as well as the lower Atlantic Coastal Plain have soils that are deficient in Co. The map below¹ shows the specific areas that are Co deficient:
This is not a problem because it appears that horses are tolerant of low levels of this mineral.
Co deficiency has never been reported in horses, and in fact has never been experimentally induced either.
If a Co deficiency were to occur, it would result in a Vitamin B12 deficiency. This would be caused because the horse derives all of its B12 from microbe synthesis.
Co toxicity is very unlikely in horses, and has never been reported. This is due to the fact that Co has a very low absorption rate.
Co is a very important mineral in your horse's diet, due to its place as part of the Vitamin B12. Hopefully this page has helped you more clearly understand this important mineral.
¹From Basic Animal Nutrition and Feeding: Fifth Edition by Wilson G. Pond.