Cows in a certain dairy herd were affected by abnormal milk secretion and the frequent occurrences of paresis. The younger cows, with 1 calving, had low magnesium (1.84 mEq) but high calcium (4.63 mEq) serum levels and the older cows, with more than 5 calvings, had low magnesium (1.68 mEq), low calcium (3.90 mEq), whereas control cows had normal levels of 2.00 mEq for magnesium and 4.28 mEq for calcium, respectively. In Cow 12, the blood serum magnesium levels decreased from 1.68 mEq to 0.64 mEq at the first onset of hypomagnesemic tetany. In Cow 1, the blood serum calcium levels decreased from 4.21 mEq to 1.42 mEq and the blood serum magnesium levels increased to 2.20 mEq from 1.39 mEq at the first onset of hypocalcemic coma. Before detectable changes, the cows were suffering from chronic hypomagnesemia. Blood samples of downer cows were obtained from 18 cows exhibiting paresis and semi-comatose state from other dairy farms. Their blood serum magnesium level was 1.54 mEq, and their blood serum calcium level was 3.40 mEq. Hypomagnesemic tetany is cause by a low intake of magnesium from roughage. This chronic hypomagnesemia of these cows must also be caused by a low intake of magnesium. Bone samples obtained from the cows from the dairy farm showed osteoporosis. Bone sample of Cow E had been fed highly concentrated the food at a private dairy farm for a year, and her osteoporosis was accelerated due to the excess of phytic acid in the food. Nephrocalcinosis was observed in some cows in the herd. Increased blood serum calcium in younger cows was released from the bone into milk and urine, which caused the bone demineralization, calcium accumulation in the kidney, and alcohol-positive milk, i.e. osteoporosis, nephrocalcinosis and “the Utrecht abnormality of milk”, respectively.