The Pathology of Hypervitaminosis D in Cattle

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Abstract
Experimental hypervitaminosis D was produced in cows by the daily feeding of 30 million U.S.P. units of vitamin D for varying periods of time. Cardiovascular mineralization was not present after 7 days, but was observed after 10 days and became extensive and widespread after 21 and 30 days. Pregnant cows developed more severe lesions than non-pregnant ones. In the heart, the lesions were more severe on the left side, and consisted of subendocardial mineralization and hemorrhage. In the elastic arteries, the degree of mineralization was maximal proximally, and diminished in severity distally. In the muscular arteries, the mineral deposits when confined to the media were accompanied by a proliferative intimal reaction. The veins were less severely affected than the arteries. Histochemically the mineral deposits contained abundant calcium and phosphorus. X-ray diffraction studies indicated the principal inorganic product of the vitamin D-induced mineralization was a carbonate hydroxyapatite, comparable in crystallochemical characteristics to that of bone.