Mineral elements are necessary components of the cells and tissues of the body. The imbalance of magnesium, potassium, phosphorus, calcium in the blood serum of animals affects the function of the cardiovascular system, contributes the development of myocardial dystrophy. Due to the intense functional activity, highly productive cows are more prone to the development of this pathology, therefore, the determination of their content of minerals during the prenatal period is relevant. To perform the study, two groups of highly productive cows of the Kostroma breed of the third or fourth lactation, which are in the prenatal period - 10-13 days before calving, were formed under the conditions of the livestock enterprise SPK "Gridino" of the Krasnoselsky district of the Kostroma region. The first experimental group was formed of 15 clinically healthy cows; the second experimental group included 5 cows with signs of myocardial dystrophy (tachycardia, weakness of heart sounds, specific ECG changes, etc.). The amount of important mineral elements for optimal myocardial function was determined in the blood serum, using the OLVEX reagent kits. The components such as magnesium and potassium, as well as total calcium and inorganic phosphorus were mathematically calculated on he basis of K:Mg and Ca:P ratio. It was found that in the blood serum of sick cows the level of magnesium was higher (1.85 times (P<0.001), against the lower values of potassium 29.57% (P<0.01), total calcium (by 10.9 %), inorganic phosphorus (by 10.8%) than in clinically healthy cows. This indicates a significant imbalance of the studied mineral metabolism components in highly productive cows in the prenatal period with myocardial dystrophy.