Calcium Mobilization in Hypomagnesemic Wethers Fed on a Low Magnesium and/or High Potassium Diet

Abstract

Four wethers were subjected to four diet treatments for 7-10 days in a 4×4 latin square design to determine calcium mobilization in hypomagnesemic sheep fed on a low magnesium and/or high potassium diet. The diet treatments were a normal diet, low magnesium diet, high potassium diet and low magne-sium/high potassium diet. On the final day of each diet feeding period, the intravenous infusion of EDTA solution at a rate of 0.263mmol/kg body weight was performed for 60 min to determine calcium mobilization during the infusion period. Mean plasma magnesium levels in animals receiving the low magne-sium, high potassium and low magnesium/high potassium diets were 0.55, 0.74 and 0.61mmol/l, respectively. They were significantly lower than those of the control diet fed-sheep. Diet treatments did not affect plasma calcium and potassium concentrations. Plasma-ionized calcium concentrations linearly de-creased during the EDTA infusion in all groups. The rate of decrease in ionized calcium tended to be greater in hypomagnesemic sheep compared with those of the control sheep. The mean calcium mobilization rates in the control, lowmagnesium, high potassium and low magnesium/high potassium diet-fed sheep during the EDTA infusion period were 4.98mmol, 3.83mmol, 3.23mmol and 3.58mmol, respectively. These results suggest that hypomagnesemic sheep whichare induced by the consumption of a low magnesium and/or high potassuim diet, could be susceptible to hypocalcemia due to depressed calcium mobilization.