Hypomagnesaemic Tetany in Cattle : I. Incidence, aetiology, diagnosis and treatment

Abstract

SUMMARY The incidence, aetiology, diagnosis and treatment of hypomagnesaemic tetany are briefly reviewed. Despite the large amount of information gathered over the last 35 years there is still insufficient knowledge of the physiological role of magnesium in the dairy cow, of factors influencing day to day requirements and of the mechanisms involved in the onset of clinical symptoms of tetany in hypomagnesaemic animals. Among the causal factors that can increase the risk of severe hypomagnesaemia are: low availability of magnesium in some foodstuffs, heavy dressings of nitrogenous and potassic fertilizers to grass swards, high milk yields and the absence of any significant mobilizable reserves in the adult bovine. There can be wide variations in magnesium requirements among individuals in a herd and hence considerable variations in serum magnesium levels so that a representative number of blood samples should be taken from survivors for diagnostic purposes; blood samples taken after death are of little diagnostic value. Treatment of the acute phase by injection should be followed by giving calcined magnesite by mouth.