Copper poisoning in sheep

Copper poisoning in sheep is seen in both the chronic and acute forms relatively commonly. Acute poisoning is usually from an accidental overdose of copper, although poisoning as a result of gradual accumulation is the cause of chronic copper poisoning. Excess ingestion leads to accumulation of copper in the body tissues most especially the liver. Sheep are particularly susceptible to copper poisoning compared with other ruminant species (McDonald et al, 2011). Some breeds of sheep are particularly susceptible to copper poisoning, such as North Ronaldsey, Texels, Sufflolks and Blue Faced Leicsters, whereas breeds such as Scottish Blackfaces and Swaledales are less susceptible to it. In this author's experience, the most common time copper poisoning is seen is when sheep are fed cake or minerals intended for cattle. Prognosis is grave once the clinical sign of jaundice appears (Scott, 2013).

Acute copper poisoning usually leads to sudden death with a very jaundiced carcass with gun metal kidneys and a bronze coloured liver on post-mortem. If the animal survives long enough to develop chronic signs and haemolysis then necrosis of the hepatic cells of the liver, jaundice, loss of appetite are seen and possibly coma leading to death. Some sheep will head press against walls because of the toxin build up in the body. In subacute cases, jaundiced mucous membranes including conjunctiva (Figure 1) can be seen with very dark red (almost black) coloured urine as a result of the haemolysis of red blood cells. Some sheep will pant excessively especially in early cases when anaemia is present.