Variations in the response of sheep to experimental magnesium deficiency

Hypomagnesaemia was induced in adult sheep by changing their diet from chaff given orally to a milk diet, low in Mg, infused via the abomasum. All sheep given the milk diet developed hypomagnesaemia and four out of 19 developed nervous convulsions similar to the natural disease grass tetany. Analysis of the sequential changes in plasma Ca, P and Mg revealed a striking positive correlation between Ca and Mg and hypocalcaemia thus appeared to be a general response to Mg deficiency. Many sheep appeared to adapt to the deficiency since after a period of about 11 days the decline in plasma Mg (and Ca) was either alleviated or reversed. However the four sheep which developed convulsions all showed a rapid and substantial decline in plasma Mg associated with a decline in plasma Ca.