Changes in the calcium phosphorus and magnesium content in the blood serum of cows during calving

: A total of 447 cows were investigated during the dry period, the period following calving, and the period of intense lactation, once each time, and other 55 cows were subjected to systemic periodical examinations in the last month prior to calving and up to the tenth day after it. It was found that the content of serum calcium and inorganic phosphorus dropped in the first days following calving in most of the animals. In about 30% of the cows calcium and inorganic phosphorus dropped as low as the lower physiologic threshold. The blood serum magnesium likewise dropped after calving, however, in the greater part of the investigated animals it remained within the normal range. The alkaline phosphatase activity became slightly weaker in the first days after calving, but in some of the cows the level of the alkaline phosphatase was lower in the period post partum.