COPPER is an essential trace element for both pastures and livestock, however livestock have a much higher requirement for copper than pastures.

Most trace mineral deficiencies are reasonably simple to deal with, copper deficiency however can be quite complicated with primary and secondary deficiencies occurring.

Primary copper deficiency in livestock can occur when pasture copper is below about 6 mg/kg dry matter (DM) however the complex interactions between copper, molybdenum, sulphur and iron mean that pasture copper concentration alone may not tell the whole story.

Copper deficiency can cause a wide range of conditions in cattle and sheep that include: changes in coat colour, loss of wool crimp and tender wool (Steely Wool), scouring, anaemia, fractures, enzootic ataxia (Swayback) and infertility.

Copper deficiency is best diagnosed via liver biopsy as blood copper levels are not a good indication of adequacy or deficiency.

Secondary copper deficiency results from a complex group of interactions between copper, sulphur, molybdenum and iron in the diet that all influence the absorption of copper (ACu) by the animal.

Molybdenum and sulphur interact with copper through the formation of thiomolybdates (TM) in the rumen which irreversibly bind copper in the gut and potentially in the blood leaving it unavailable to the animal.

The effect of TM binding of copper increases with increasing dietary molybdenum and sulphur to reduce the ACu.

This combined effect is greatest in pastures and least in silages with molybdenum having very little impact on the ACu in silage.

Given these interactions, the dietary copper needed for a 500 kilogram cow producing 20 litres of milk per day could vary from 5 mg/kg DM to as much as 20 mg/kg DM.

Copper availability can also be influenced by iron levels in the diet through the formation of insoluble complexes.

Iron intake can be increased during close grazing of pastures due to soil ingestion or through high iron in the water supply.

Interactions with other trace minerals and copper can occur but are of limited importance compared to sulphur, molybdenum and iron.

Treatment of copper deficiency in livestock depends on whether it is a primary deficiency or a secondary deficiency.

Primary deficiencies are easily treated with copper supplementation of livestock via injectable copper, rumen boluses or inclusion of supplementary copper in grain or pellets.

Long term application of copper to pastures with fertilizer will increase soil and plant copper levels and generally resolve livestock deficiencies.

Secondary copper deficiency is far more difficult to treat.

Supplementation with copper via rumen boluses or other dietary sources may not be sufficient to overcome binding by TM in the rumen and intestine.

Similarly, if there is very high levels of TM escaping the rumen and accumulating in the blood, this too may bind copper even if administered via an injectable supplement.

In feed supplementation with copper–amino acid complexes may allow more copper to escape TM binding in the rumen resulting a higher ACu for the animal.

A glass rumen bolus is now available in Australia containing a rumen soluble source of copper that the manufacture claims can bind TM in the rumen.

It stops TM either accumulating in the blood stream or binding copper in the lower intestine allowing enough copper to be absorbed from the rest of the diet by the animal to correct a secondary copper deficiency.

If you suspect copper deficiency in any stock, it is important to obtain a definitive diagnosis through liver biopsies and plant tissue testing for either primary or secondary deficiency.

Whatever supplementation method is appropriate in different situations, regular monitoring of the copper status of livestock is also important.

Copper is potentially toxic and can accumulate in the liver quickly if livestock are over–supplemented or supplemented in ways where individual animal intakes are not closely controlled.

Talk to your vet or nutritionist for more information on copper deficiency, testing options, supplementation options and the risk of toxicity.