Metallic electrolyte partially ionized in plasma and stored mainly in bone and muscle tissue. Most metabolic processes require it. Forage feeds are generally quite rich in magnesium and dietary supply is normally adequate to meet requirements. Deficiency is uncommon but would produce weakness, nervousness, muscle tremors and cramps. Magnesium, as the sulphate or aspartate is used by some horse owners in an attempt to calm horses, and historically magnesium sulphate was used intravenously as an anaesthetic. The value as a calming agent has yet to be confirmed experimentally.
