[The levels of various mineral substances in the blood plasma of bovine fetuses and their mothers in the third trimester of pregnancy].

The levels of total calcium, inorganic phosphorus, magnesium, sodium, potassium, and chlorides in the blood plasma, and the osmolality of the plasma, were determined in bovine foetuses (n = 20) and the dams (n = 20) in the third trimester of gravidity. The cows of the Bohemian Spotted breed were 2.5 to 7 years old. The foetuses were taken from the uterus by the Caesarean section with local anaesthesia. The foetuses were of both sexes (nfemale = 12, n male = 8). Only the level of total calcium and inorganic phosphorus in the blood plasma was much higher in the foetuses than in the dams and this difference was highly significant. The levels of other minerals showed no statistically significant differences in the two categories of animals tested. The osmolality of the blood plasma of the foetuses was almost the same as in the cows. The higher calcaemia and phosphoraemia of the foetuses ensues from the function of osteotrophic minerals in the process of quick growth and ossification in the third trimester of intrauterine life. The closeness of the levels of sodium, potassium and chlorides as well as the very similar osmolality of the blood plasma in the foetuses and the dams prove the "stability" of the dynamic balance of these parameters between the foetus and the dam in the internal environment of the womb.