Milk fever, or parturient paresis, is the second most common disease in Swedish dairy cows. The disorder is associated with the onset of lactation when some cows are unable to meet the metabolic demands of calcium to support milk production and therefore develop a state of hypocalcaemia. Clinical hypocalcaemia (milk fever) may lead to coma and death in severe cases but subclinical hypocalcaemia has also been shown to have negative effects on e.g. feed intake and production and to increase the susceptibility of the cow to develop secondary diseases. The nutritional strategy applied precalving is of great importance in preventing milk fever and e.g.