The amount of calcium, phosphorus and magnesium in milking cows, blood was tested and it is one of indicators that cows were fed with these substances. The average amount of calcium, phosphorus and magnesium in blood of milking cows was tested and it is one of indicators that cows were fed with these substances. The average amount of calcium in tested cows, blood is 2.82 mmol/l, the average amount of phosphorus is 1.66 and the average amount of magnesium is 1.29 mmol/l. Cows, were fed by corn silage, alfalfa hay, along with concentrate of standard mineral composition.Ispitivan je sadržaj kalcijuma, fosfora i magnezijuma u krvnom serumu krava, kao jednog od indikatora obezbeđenosti životinja ovim elementima. Prosečan sadržaj kalcijuma u krvnom serumu ispitivanih krava iznosio je 2.82 mmol/l, fosfora 1.66 mmol/l i magnezijuma 1.29 mmol/l seruma. Krave su hranjene kukuuznom silažom, senom lucerke i krmnom smešom za krave muzare