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Cobalt
Written by John Turner Consultancy for Agrifert
Cobalt is an essential trace element for the nutrition of all ruminant animals.Rumen microbes produce vitamin B12 of which cobalt is an essential component.
Vitamin B12 is requiered for the absorption of some of the products of rumen fermentation so deficiency produces symptoms rather like starvation of the animal.
Symptoms of deficiency:
These include reduced growth rate, decreased appitite, decreased milk production, rough hair coat, weight loss, weak animals, increased susceptibility to parasites, incresed risk of disease or infections and increased mortality of young animals.
Reduced conception rates can be expected from cobalt deficiency during the period (2 months) before mating, all female animals will be affected however the worst affected will be heifers, ewe hoggets and 2-tooth ewes.
Different classes of livestock have different requirements for cobalt or vitamin B12.
Lambs have the highest requirement followed by calves, adult sheep and adult cattle. For any species young animals are more likely to be affected by cobalt deficiency than fully grown animals. In a dairy farm situation, an indicator of cobalt deficiency is slow growth rate of weaned calves.
Factors that influence the cobalt content of pastures:
There is a reasonable correlation between soil cobalt level and the cobalt content of pastures so soil testing for this element is used as a general indicator of cobalt status and to predict if application of this element to the soil is a reasonable treatment option.
The composition of pasture is a significant factor that influences animal uptake of cobalt. Ryegrass has roughly double the cobalt content of low fertility grass species such as browntop and clover has about 1.5 times the content of ryegrass. Management aimed at increasing the clover content of pastures and reducing the content of 'low fertility' grass species will be beneficial. This includes increasing the soil pH and levels of nutrients such as phosphorus.
Level of Cobalt required in pasture or feed:
Although adult cattle may not be affected by levels as low as 0.06 mg/kg in the pasture if fully fed however a safe minimum level is considered to be 0.10 mg/kg to cater for the requirements all ages of cattle on a property. To quantify this amount of cobalt, 0.10 mg/kg is the same as 0.1 gram per 1000 kg dry feed/
Sheep, goats and deer pastures should also be maintained at a level of between 0.10 and 0.10 mg/kg especially for young animals being weaned onto pasture.
Options for Cobalt application:
For many years, cobalt has been included in solid fertiliser blends however the efficiency of uptake may be low (possibly less than 5%) and there is a time lag between soil application and uptake by pastue plants. The distribution of cobalt over an area fertilised with a bulk blend may also be uneven and the timing of application may not be ideal for meeting the seasonal requirements of sensitive classes of stock.
Cobalt applied as a foliar treatment is effective on all pasture types and there is no time lag between application and when the element is available to grazing animals. The rate required for effective treatment is much lower than for soil application. Application may be targeted onto pastures for young stock.
Vitamin B12 injection directly into stock is a good option but the beneficial effect is not long term
Multimineral additives to salt blocks or to stock drinking water may be beneficial however the amount of any one element included is usually not adequate for 'deficient' stock.