The Association of Plasma Magnesium Concentration and Thyroid Gland Activity in Young Calves

Summary Hypomagnesaemia was induced in young calves 1—2 weeks old by feeding them a diet composed of skimmed milk and barley straw to which urea, potassium chloride and soya‐bean oil were added. Blood samples were collected from each calf once a week from the jugular vein until there was a significantly lower (P < 0.01) plasma magnesium concentration in the experimental compared to the control calves receiving MgO instead of KCl. The blood samples were analysed for plasma glucose concentration and thyroid hormones as well as for plasma magnesium concentration. The Tree Thyroxine Index (FTI) values were lower (P<0.05) and plasma glucose concentrations higher (P <0.01) in the experimental calves than in the control calves. The results suggest that experimentally induced hypomagnesaemia is associated with a reduced thyroid gland activity and elevated plasma glucose concentration in young calves.