Dietary Citrate and Hypomagnesæmia in the Ruminant

THE sudden onset of clinical hypomagnesaemia in the lactating cow most commonly occurs soon after the change from stall feeding to grazing fresh spring grass, and in the absence of any marked reduction in intake of magnesium. This condition is probably brought about by reduced absorption of magnesium; but the reasons for this are not fully understood. Marked reductions in output of urinary magnesium on changing the diet from hay or grass nuts to fresh grass have been described for sheep1 in spite of increased intakes of magnesium; this probably indicates reduced absorption. Care2 recently calculated that a 50 per cent reduction in absorption could lead to the development of hypomagnesaemia within 7 days in sheep.