The Effects of Intramuscularly Administered Vitamin D3, 25- and 1α-Hydroxycholecalciferol in Cows on Plasma Mineral Content, Plasma 25-Hydroxycholecalciferol and on Mineral Deposits in Soft Tissues

Summary The investigations were carried out to evaluate potential side effects of a prophylaxis with high doses of vitamin D3 and vitamin D metabolites in parturient paresis. For this reason, 107 IU vitamin D3 (= 250 mg), 4 mg 25-OHD3 or 420 μg 1α-OHD3 were applied to non-gravid dairy cows at the end of lactation. The application was repeated 3 times at one week intervals and the changes of the mineral concentration and 25-OHD were measured in the plasma. The pathomorphological changes in the cardio-vascular system and other organs were examined macro-and microscopically. The application of vitamin D3 and 25-OHD3 led to an immediate and continuous increase of the 25-OHD concentration in the plasma. On the other hand, administration of 1α-OHD3 resulted in a decrease of the 25-OHD level. After the application of vitamin D3 and 1α-OHD3, the Ca and Pi concentration increased significantly. After 25-OHD3, the Ca concentration decreased below the initial level in the second week. The administration of all 3 compounds led to a significant decrease of the Mg concentration after the first injection. The administration of vitamin D3 and 1α-OHD3 resulted in a significantly more pronounced calcinosis of inner organs while after the application of 25-OHD3 only occasionally calcium deposits were observed in the vascular system.