This fact sheet was developed by students enrolled in Purdue's ANSC 442 Sheep Management course in Spring 2001, as a semester project. These fact sheets provide useful information on various topics related to sheep. View the list of fact sheets.
Copper Toxicity in Sheep
Copper is an essential nutrient for sheep. Copper is required, but is also highly toxic. Copper is required for normal melanin production, elastin and collagen synthesis, iron metabolism, and the integrity of the nervous system. Copper is also known to be important for effective immune responses. The true importance of copper may be understood from looking at the problems associated with copper deficiency. Deficiencies are not often seen in the US. Common signs of copper deficiency are neonatal ataxia or "swayback", degeneration of the myelin sheath of nerve fibers, and wool that lacks strength, crimp, elasticity, and pigment. Copper toxicity is more commonly seen and will prove to be more of a problem.
Copper is regularly used in the diet at about 8-11 parts per million. It may be toxic to sheep at 15-20 parts per million. There is a narrow difference between the amount of copper required and what will be toxic to the animal. A diet should never have copper level above 25 parts per million to be safe for most sheep.
How does toxicity occur?
The liver of the sheep stores copper extremely efficiently. The normal range of copper levels for the liver is 6 parts per million to 279 parts per million. This is due to an adaption of sheep in copper deficient areas. The average animal can live without copper for 4-6 months just on the liver supply. This copper builds up over time. Once the build-up reaches a certain threshold, the copper may spill into the bloodstream. This threshold is about 1,000 to 3,000 parts per million. The spilling of the copper into the bloodstream causes hemolytic crisis. This is brought on by physiological stress. The physiological stress may be caused by many different things.
Toxicity and Prevention
Copper toxicity is caused by many nutritional problems. Sheep are not able to have the same levels of copper in their feed as other animals such as cattle or swine. Sheep may display signs of toxicity when as little as 10 parts per million of copper is added to the diet. In many parts of the country where adequate levels of copper is found in the pastures, it is not necessary to add copper to the diet. Copper toxicity may result from low levels of, molybdenum, sulfur, zinc, and calcium. The most important factor is the copper to molybdenum ratio. A ratio of 10:1 will prevent toxicity. Zinc will reduce copper absorption. By eliminating trace minerals, we will see an amplified toxicity of copper because of the important affects of the other minerals and copper. Some plants consumed by sheep may cause a toxicity. Lupines, a type of plant, contain toxic alkaloids that impair the liver's ability to metabolize ingested copper. Feeding sheep diets made for other animals can be devastating. For instance, copper is used to promote the growth in swine and will be added in large amounts. The diet of sheep must be carefully balanced to prevent copper toxicity. The levels of trace minerals and the forage intake must be considered.
Should we add an excess of 25 ppm of copper to your diet?
Both sexes of sheep are susceptible to copper toxicity. Young animals are more susceptible to the toxicity. However, mature British breed ewes are the most susceptible. These breeds include Suffolks, Oxfords, and Shropshires. Texels from Netherland are the most susceptible. Finnsheep are the least likely to develop a copper toxicity. Merino sheep have an intermediate occurance of copper toxicity.
Clinical Signs of Copper Toxicity
Sheep will suddenly go off feed and become very weak. The mucous membranes and skin will turn a yellowish brown. Hemoglobin is present in the urine turning it a dark red-brown. Death will occur about 75% of the time, depending on the severity of the toxicity. When the corpse is necropsied, the liver will be pale tan and the kidneys will be dark greenish black.
Treatment may be effective if the level of toxicity is low and is diagnosed right away. The animal needs to have the source of the copper removed. The animal should not be subjected to any stressful situations that may lead to hemolytic crisis. Copper may be inactivated with molybdate and sulfate. The animal may also be drenched with electrolytes and sodium thiomolybdate to flush the kidneys and bind the copper. This is done orally at a rate of one quart per hour.
Created by: Alicia Bagnall