[Mineral levels of the arterial and venous blood in cows].

The values of calcium, phosphorus, magnesium, potassium and sodium in the arterial and venous blood of cows before and after milking two to three months from calving were found to be within the standard range. The differences are not significant. In venous blood the values are lower than in arterial blood, which proves that minerals are utilized by the organisms for milk production. The values of minerals in the blood of the Slovak Spotted cows are higher than in the blood of the Black--Pied Lowland cows; they are also higher in the blood of lower-performance cows than in the blood of cows giving high milk yields. This means in practice that Black-Pied Lowland cows and high-performance cows need a higher supply of minerals to their blood stream.