Vitamin B12
Vitamin B12 (cobalamin) is essential for cell division and is therefore particularly important for tissues with a high cell turnover, e.g. the intestinal mucosa and nervous tissue. It also influences blood formation and the synthesis of the amino acid methionine. The central atom of vitamin B12 is cobalt, hence the chemical name cobalamin.
Vitamin B12 is not present in plant-based feedstuffs. However, if the feed contains sufficient cobalt, the microbes in the colon usually provide the horse with an adequate supply of vitamin B12. There is therefore no official supply recommendation.
However, in the case of insufficient hay rations, poor hay quality, or chronic gut disorders such as watery droppings, supplying vitamin B12 can be beneficial. No harmful effects from vitamin B12 overdose have been described in horses.