Sheep are uniquely sensitive to copper accumulation, making copper toxicity a significant welfare concern when dietary management or supplementation is poorly controlled.
Copper toxicity in sheep causes profound suffering at multiple stages. During the subclinical accumulation phase, affected sheep may show subtle lethargy and reduced production without obvious distress. The haemolytic crisis, however, is a severe acute welfare emergency: sheep experience rapid-onset systemic collapse, profound anaemia, organ failure, and extreme weakness. Death can occur within hours. The crisis is often triggered by additional stressors — transport, weaning, bad weather — meaning animals already under welfare pressure are pushed into catastrophic organ failure. The preventability of this condition makes it particularly significant: careful feed management, avoidance of cross-species feeding errors, and routine monitoring of high-risk flocks can prevent the vast majority of cases and eliminate this source of preventable suffering.