[Comparative effects of magnesium deficiency and overload on calcium and phosphorus metabolism in the growing pig].

This study was designed to assess the influence of dietary magnesium on calcium and phosphorus metabolism in growing pigs. 18 4-month-old pigs received either an Mg-deficient (40 ppm), an Mg overload (5,600 ppm) or a control Mg diet (1,000 ppm) for 70 days. The following parameters were measured: kinetics of plasma concentrations of Ca, phosphates, Mg and alkaline phosphatase (AP), absorptions, urinary and fecal excretions, retentions of Ca, P and Mg, soft tissue and bone mineral contents (BMC), and intestinal mucosal CaBP (calcium-binding protein) and AP activities. Dietary Mg level had no effect on calcium and phosphorus metabolism as far as Ca and P absorptions and retentions, BMC, intestinal CaBP and plasma levels of Ca, P and AP are concerned. Mg overload significantly decreased urinary P excretion and increased kidney P content, but did not change fecal P excretion. Jejunal AP activity was slightly decreased in Mg-deficient pigs. The plasma, bone, urinary, fecal, absorbed and retained Mg varied linearly with Mg intake (r: 0,85-0.96). In Mg-deficient pigs, hypomagnesemia appeared after 1 week and its severity did not increase with time. In Mg-overloaded pigs, hypermagnesemia occurred very late and was limited. This suggests that, in the growing pig, dietary Mg has little or no effect on Ca-P metabolism. It may also be concluded that growing pigs are rather resistant to Mg deficiency since no clinical symptoms were observed.