Hyperlipaemia is a life-threatening disease to which donkeys are particularly prone, both as a primary or secondary condition. The matabolic pathways are complex, involving many factors. Basically, hyperlipaemia occurs when animals mobilise triglyceride from body fat reserves in response to a negative energy balance achieving plasma levels over 5 mmol per litre. The end result is multi-organ failure as lipid is deposited in the liver and kidneys. The initial clinical signs are easy to miss, especially in donkeys and, if early treatment is not initiated, the disease will progress rapidly to terminal stages.