I had a question come up today about copper toxicity in sheep. Of all our domestic animals, sheep are the most susceptible to copper toxicosis.
Copper is a required mineral in all species, but sheep have a narrow range between how much copper is adequate and how much is toxic. Most cases of copper poisoning in sheep occur when they are fed rations or minerals designed for other species that are more tolerant of copper.
When sheep are fed such diets over a period of time, copper builds up in the liver because sheep do not excrete copper as efficiently as other animals. When the liver becomes saturated with copper, massive amounts of copper are released into the bloodstream, resulting in tissue damage. This sudden onset is often triggered by some stressful event.
Note on the Mineral Wheel, that both molybdenum and sulfur act as antagonists to copper and have a protective effect if there is excess copper, The presence of these compounds bind with copper and prevent gut absorption and increase excretion of copper.
Sheep do well on ABC’s cafeteria-style mineral program, and I have never encountered copper toxicosis in sheep on this program even though it does provide a free-choice source of copper. Animals will balance their own mineral needs if given the choice.