Ruminant animals are unique in their ability to supply their own requirements of essential vitamin B12.
In a classic example of symbiosis, microorganisms within the goat rumen utilize dietary cobalt to synthesize vitamin B12 which is then available to the host animal.
Vitamin B12 is an essential coenzyme in the major pathway through which propionate and several amino acids are metabolized. Propionate, derived from rumen fermentation of plant celluloses, is the main precursor of glucose in the ruminant.
The clinical signs of cobalt deficiency in ruminants are in fact, due to reduced tissue vitamin B12 concentrations and a breakdown of this glucose pathway.
Cobalt deficiency in ruminants causes unthriftiness, “weepy” eyes, severe wasting and eventually death if sufficiently severe and prolonged. Mild cobalt deficiency is easily confused with unthriftiness caused by underfeeding, heavy worm burdens or selenium-responsive illthrift. Cobalt deficiency can only be accurately diagnosed in livestock by tests for vitamin B12 in blood or tissues.
In Victoria, cobalt deficiency has been identified in sheep along the coastal fringe of western Victoria and southeast Gippsland, and isolated areas further inland. It commonly occurs also in coastal areas in other States.
The disease has not been recognized in goats, but more recent studies indicate that specific areas of the southern mountain districts particularly, provide only marginal dietary cobalt for goats. In low cobalt areas, lambs are most sensitive to deficiency followed by ewes, calves and cows in that order. Severe signs are seen only rarely in cattle in Victoria. Cobalt deficiency can be cured and prevented by providing supplementary cobalt or vitamin B12:
Injections: Vitamin B12 must be given by injections, vitamin B12 drenches are not recommended.
A 1-2 mg dose should last 2-3 months and is the preferred method of treatment.
Drenches: Cobalt sulphate must be given as a drench, and can be combined with some anthelmintics and other trace elements, copper and selenium.It must be administered weekly to be effective.
A suitable drench recipe dissolves 15 g cobalt sulphate in 1 litre of water: Give goats 2 ml. Large doses of cobalt are poisonous.
Bullets: Cobalt bullets are administered to individual animals, lodge in the rumen and continuously release the trace quantities of cobalt required. Recent evidence indicates that bullets are effective for only 14 weeks in sheep.
Topdressing: Cobaltised superphosphate is a suitable method of treating grazing goats. It is not definitely known if autumn applications always provide sufficient cobalt for the following springâ€™s kids and close monitoring is advised. Pastures can also be sprayed with dilute solutions of cobalt sulphate (140 g/ha) as an interim treatment.
Licks: Cobalt salt licks should contain up to 100g/t cobalt sulphate and should be provided in the ratio of 1 block per 50 goats. Some animals, usually those most in need, fail to lick the blocks and do not get their requirement.