Cobalt
Cobalt functions as a component of vitamin B12 (cobalamin). Ruminants are not dependent on a dietary source of vitamin B12 because ruminal microorganisms can synthesize B12 from dietary cobalt. The amount of dietary cobalt converted to vitamin B12 in the rumen has ranged from 3 to 13 % of intake. Supplementation of cobalt in the diet is known to increase the synthesis of ruminal vitamin B12.