Copper toxicity is a serious and often fatal condition in sheep caused by accumulation of copper in the liver, typically from inappropriate supplementation or feeding of cattle or pig feeds.
Copper toxicity causes catastrophic welfare harm. The haemolytic crisis involves rapid destruction of red blood cells causing severe anaemia, jaundice, and organ failure. Affected sheep deteriorate dramatically within hours of the crisis, progressing from apparently healthy to collapsed and dying. The suffering is acute and severe, and mortality rates are very high even with aggressive treatment. Most cases result from preventable management errors including feeding inappropriate feeds or over-supplementing copper. Vigilance about what feeds and supplements sheep are given is essential welfare management for a species with such narrow copper tolerance.