Sheep are highly sensitive to copper toxicity compared to cattle, and over-supplementation or access to copper-rich feeds causes severe welfare-compromising liver disease and haemolytic crisis.
Copper toxicity in sheep causes a biphasic welfare crisis. During the accumulation phase, sheep may show no obvious signs despite ongoing liver damage. The haemolytic crisis is sudden and severe, causing rapid breakdown of red blood cells, jaundice, dark-colored urine, weakness, and rapid deterioration to collapse and death over 24-48 hours. The crisis is extremely distressing with affected sheep showing profound weakness, inability to stand, and rapid cardiovascular deterioration. Treatment is often unsuccessful once haemolytic crisis is established. The preventable nature of copper toxicity, which arises from inappropriate supplementation or feed access, makes it a welfare tragedy that should not occur in well-managed flocks.