Copper poisoning in sheepJaundice of the sclera and conjunctiva in a sheep with chronic copper poisoning

The Agri-Food and Biosciences Institute is warning farmers about the risk of chronic copper poisoning after seeing a rise in the number of sheep killed as a result of copper poisoning in Northern Ireland.

AFBI disease surveillance laboratories at Stormont and Omagh saw peak numbers of cases of chronic copper poisoning in sheep during the summer of 2015.

AFBI said toxicity was most frequently observed in Charollais, Texel and Suffolk breeds. Growing lambs are also more susceptible than adult ewes.

See also: Dairy farmers could poison cows by feeding too much copper

Clinical signs of copper poisoning

  • The eyes and skin become jaundiced
  • Sheep spend time wandering aimlessly or head-pressing
  • Sheep become weak
  • Breathing becomes shallow and rapid, caused in part by the development of anaemia
  • Postmortem examination reveals an orange liver, black kidneys and red/brown urine.

Sheep are particularly susceptible to the toxic effects of excess copper with clinical disease following a period of excess intake.

It occurs when the liver’s capacity to store excess copper is exceeded and there is a sudden release of copper.

This typically occurs after weeks or months of accumulation of copper and often coincides with a period of stress on the animal.

The sudden release of copper by the liver causes haemolysis and irreversible damage to the kidney and the brain. Copper poisoning is slow to develop but sudden in onset.

Feeding concentrates containing high levels of copper, excessive administration of copper-containing mineral supplements or boluses, and grazing pastures which have been dressed in pig slurry are typical scenarios in which cases of copper toxicity in sheep may develop.

However even a diet with an acceptable copper concentration can also cause subclinical toxicity if fed for long enough to vulnerable breeds.

Risk

A spokesperson from AFBI added: “This is because copper is a cumulative poison with the combination of daily exposure and prolonged feeding playing a part.

“Every opportunity to reduce the concentrate intake between lactations should be taken.

“Particular care should be taken with rams as they are usually fed concentrates more regularly and for more prolonged periods.

“The best way of managing this condition is to minimise long-term concentrate use in the diet.”

Treating copper poisoning

  • Treatment options are only effective in the early stages of clinical onset
  • The aim should be to prevent clinical disease in at-risk animals by either orally dosing animals or subcutaneously injecting them with ammonium tetrahiomolybdate to strip copper from the liver
  • Copper antagonists such as molybdenum and sulphur can be added to the diet to prevent further accumulation of copper
  • Contact your vet for advice