[Levels of osteotrophic mineral elements (total calcium, inorganic phosphorus and magnesium) in the blood plasma of calves up to the age of 4 months].

In the post-natal period (up to the age of four months), healthy heifer calves of the Bohemian Spotted breed (n = 204) were studied for the levels of total calcium, inorganic phosphorus, and magnesium in the blood plasma. The calves were divided into 17 age groups (n = 12), the age interval between the groups being one week. The highest level of total calcium was found in the calves in the first week after birth (11.77 mg%); this level significantly decreased with higher age of the calves. The minimum was recorded in the fifth week (10.13 mg%). The level of inorganic phosphorus was almost unchanged throughout the period under study, ranging about 9 mg% with insignificant variation. The level of magnesium in the plasma was also fairly stable in the first month of age (2.14--2.29 mg%), a slight increase being observed only from the fifth week on. The comparison of the valves measured in the calves with those obtained in cows indicated that the level of calcium (except the value measured in the fifth week) was higher in the valves than in the cows throughout the experimental period, and that the level of phosphorus was also significantly higher than in the cows throughout the same period. Average values of magnesium in the plasma of the calves were mostly lower than in the plasma of the cows; only in the last third of the experimental period were the magnesium levels very close to, or higher than, the levels in the cows. The dynamics of the development of the cations studied in calf plasma, the Ca/P, Ca/Mg, P/Mg, (Ca+Mg)/p ratios, and the ion product Ca. P reflect the function of these osteotrophic minerals in the process of the growth of skeleton.