The effect of induced hypomagnesaemia and hypermagnesaemia on the erythrocyte magnesium concentration in cattle.

Hypomagnesaemia was induced in ten yearling Friesian heifers by starving them for forty hours while hypermagnesaemia was induced in seven Friesian calves (about two and half months old) by intramuscular magnesium sulphate (MgSO4) injection. The plasma magnesium (PMg) concentration decreased (P less than 0.05) during starvation and increased (P less than 0.05) following MgSO4 administration. However the erythrocyte magnesium (EMg) concentration did not show any significant change either with starvation or following the MgSO4 administration. These results show that sudden and significant changes in PMg concentration do not have any significant effect on EMg concentration. Accordingly EMg concentration may be a better indicator of long-term body Mg status and during hypomagnesaemic tetany could show whether the decrease in PMg concentration was sudden or gradual.