[Calcium, inorganic phosphorus and magnesium in the serum of pregnant cows]

Each of the three elements: calcium, inorganic phosphorus and magnesium was determined 440 times in serum of cows in two groups during one year. The experimental group was formed of 30 pregnant cows, and the control group of 10 not fertilized cows. Parallelly to these determinations mineral nutrition of the cows studied was recorded. The content of calcium in serum of the experimental cow group was maintained on the physiological level, only 4 days before delivery a decrease in calcium content below the physiological level was observed. The content of inorganic phosphorus in serum of the experimental cows decreased with progressing pregnancy, however, it was maintained on the physiological level. In control cows the content of both elements (calcium and inorganic phosphorus) in serum was maintained on the physiological level during the whole investigation period. The content of magnesium in serum of cows in both groups remained on the physiological level over the whole period of studies. From the tabular calculations it appears that the cows received excessive calcium in fodder in one year, which exceeded several times their demand; the increased supply did not, however, effect its increased content in serum of the cows in both groups. The supply of phosphorus in fodder did not cover its demand in pregnant cows almost during the whole period of the studies.