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Primary chronic poisoning is seen most commonly in sheep when excessive amounts of copper are ingested over a prolonged period. The toxicosis remains subclinical until the copper that is stored in the liver is released in massive amounts. Blood copper concentrations increase suddenly, causing lipid peroxidation and intravascular hemolysis. The hemolytic crisis may be precipitated by many factors, including transportation, lactation, strenuous exercise, or a deteriorating plane of nutrition.
Phytogenous chronic poisoning is seen after ingestion of plants, such as subterranean clover ( Trifolium subterraneum ), that produce a mineral imbalance and result in excessive copper retention. The plants that are not hepatotoxic contain normal amounts of copper and low levels of molybdenum. The ingestion of plants such as Heliotropium europaeum or Senecio spp ( Pyrrolizidine Alkaloidosis: Introduction) for several months may cause hepatogenous chronic copper poisoning. These plants contain hepatotoxic alkaloids, which result in retention of excessive copper in the liver.
Acute poisoning may follow intakes of 20-100 mg of copper/kg body wt in sheep and young calves and of 200-800 mg/kg in mature cattle. Chronic poisoning of sheep may occur with daily intakes of 3.5 mg of copper/kg body wt when grazing pastures that contain 15-20 ppm (dry matter) of copper and low levels of molybdenum. Clinical disease may occur in sheep that ingest cattle rations, which normally contain higher levels of copper, or when their water is supplied via copper plumbing; cattle are more resistant to copper poisoning than sheep, and thus are not affected in these instances. Young calves or sheep injected with soluble forms of copper may develop acute clinical signs of toxicity. Copper is used as a feed additive for pigs at 125-250 ppm; levels >250 ppm are dangerousalthough as for sheep, other factors may be protective, eg, high levels of protein, zinc, or iron. Chronic copper toxicosis is more apt to occur with low dietary intake of molybdenum and sulfur.
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Pictures below are from a 3 year old ewe that died suddenly of Copper Toxicity
This page was last updated on: January 6, 2008