Vet's View: Fatal problems caused in ruminants by copper toxicity

Intakes

Land treated with pig or poultry manure can also create a risk of excess copper intakes, as well as unintentional overdose which could occur via accidental consumption of cattle concentrate or if drenching for deficiencies.

Poisoning occurs when an animal’s liver capacity for storing copper is exceeded, resulting in the sudden release of copper into the bloodstream and the subsequent liver damage, destruction of red blood cells and jaundice.

Associated clinical signs are sudden in onset, with animals affected initially becoming visibly weak.

Steph Prior, of Penbode Vets, part of VetPartners, says: “Symptoms may not be visible until the point at which the liver is overloaded with copper, which is why the disease appears to come on quickly. As it progresses, sheep may be seen head-pressing or appear disorientated and jaundice will typically develop around the eyes, with breathing becoming shallow as anaemia develops.

"Diagnosis is typically easy to pick up at post-mortem as the liver appears bronze coloured, but beforehand can be made based on housing and feeding history where clinical signs have been seen.”

Breed susceptibility is also variable, explains Ms Prior, with the North Ronaldsey particularly susceptible alongside some of the continental terminal breeds including the Texel and Suffolk, due to their ability to absorb dietary copper.

Mindful

Given the process is one which usually takes place over a period of time, being mindful that rations fed are balanced is crucial as a preventative measure.

“Copper toxicity occurring is a result of the amount of copper being fed so, even if a ration does not contain significant amounts of copper, exposing animals to a low level over a prolonged period of time can cause a problem.

"There is a treatment option which involves stripping copper from the system, but it is expensive and comes with no guarantee it will work, so is generally not a viable option for most commercially- run systems.”

In the absence of an effective or financially viable treatment option for commercially-run animals, preventing copper toxicity by avoiding the feeding of a copper-rich diet is considered the best management approach.

“Copper antagonists such as molybdenum, sulphur or, to a degree, iron, could be added to a ration to prevent the liver taking on and accumulating copper to the same levels. Issues generally occur when diet is unintentionally over-supplemented so, as a rule, animals, especially if on more intensive rearing systems, should not be supplemented unless there is known deficiency.

“In instances where this is required, it is difficult to feed for just one so be mindful that animals are not receiving excess quantities of copper when feeding for other known deficiencies such as cobalt. Once clinical signs are present, there is little that can be done to reverse the process and the damage that has been done. Prevention is key.”

High-risk sources

THE availability of dietary copper varies between different feeds. Feeds with high concentrations of available copper include:

■ Pasture, silage and root crops grown on ground, to which large quantities of pig or poultry manure has been applied

■ Distillery by-product feeds, such as distillers dark grains produced from copper stills. Concentrate feeds containing palm oil or molassed sugar beet pulp, though wholegrain cereals are relatively poor sources of copper

■ Other potential sources of copper include cattle minerals, copper sulphate foot baths and fungicide-treated timber

Source: The National Animal Disease Information Service