The only known animal requirement for cobalt is as a constituent of Vitamin B12, which has 4% cobalt in its chemical structure. This means that a cobalt deficiency is really a vitamin B12 deficiency. Microorganisms in the rumen are able to synthesize vitamin B12 needs of ruminants if the diet is adequate in cobalt. Ruminants must consume cobalt frequently in the diet for adequate B12 synthesis.
Cobalt deficiency causes lack of appetite, lack of thrift, severe emaciation, weakness, anemia, decreased fertility, and decreased milk and wool production. Weeping eyes, leading to a matting of wool on the face, is another common symptom. Sheep are more susceptible to cobalt deficiency than cattle Cobalt deficiency also impairs the immune function of sheep which may increase their vulnerability to infection with worms.
The diagnosis of cobalt deficiency is usually based on blood (serum) vitamin B12 concentrations, which reflect immediate cobalt intake. Short-term supplementation of sheep with cobalt is usually acheived through oral drenching with cobalt sulfate or vitamin B12 injections.