Alfalfa and yeast or rich sources of cobalt, and cereal grains contain moderate amounts. | Photo: iStock

Cobalt is a rich dark blue-colored trace mineral naturally found in the Earth’s crust. Microbes in the equine hindgut use cobalt to make vitamin B-12 (cyanocobalamin) through the process of fermentation. Vitamin B-12, in turn, plays a role facilitating protein synthesis, and carbohydrate and fat metabolism. Cobalt, integrated into vitamin B-12, also promotes red blood cell formation.

Requirements and Dietary Sources

Cobalt is required in very small amounts in the equine diet. According to the National Research Council’s (NRC) Nutrient Requirements of Horses (2007), an average 1,100-pound (500-kilogram) horse only needs about ½ milligram of cobalt in his diet per day, although most horses typically consume a little more. (For reference, a sugar packet and a raisin each weigh about 1 gram, and 1 mg is 1/1000 of one gram!) Horses don’t typically doesn’t require cobalt supplementation.

Cobalt toxicity is unlikely to occur naturally in horses, although the true upper limit has not been established. The NRC’s maximum tolerable intake for horses is based on what’s known in other species, such as cattle, sheep, and swine, and is suggested to be approximately 25 milligrams per kilogram (11.4 milligrams per pound) of dry matter feed per