Plays an important role in B12 formation, which plays a key role in energy metabolism. Cobalt is really important for the rumen microbes to synthesise vitamin B12. Cobalt is also believed to play a role in certain enzyme reactions. While it can be hard to get exact inclusion rates 0.1mg/kg has been quoted. Sheep are more prone to cobalt deficiency, particularly young growing lambs. This can be attributed in part to it being involved in wool growth.