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Some Effects of a Vitamin D Deficiency on Mature Dairy Cows

Dairy Department, South Dakota State College, Brookings, S. Dak.

ABSTRACT

Detailed observations on three liberal-milking cows and one dry, pregnant cow kept under vitamin D deficient conditions have been presented. Under these conditions the total calcium of the blood plasma declined to one-half normal values, and the inorganic phosphorus to one-fifth normal. The animals became stiff, the knees bent forward, the spine became rigid and in severe cases assistance was necessary before the cow could get up. Balance trials run while these conditions prevailed showed that significant drafts on the calcium and phosphorus reserves were being made. When vitamin D was administered the losses were immediately changed to unusually large retentions. The curves showing the calcium and phosphorus concentration in the milk are remarkably smooth and coincide closely with similar curves for previous normal lactations. Calves produced after the cows had been under the deficiency conditions for some time showed visible rachitic appearances but blood chemistry and histological studies revealed no abnormalties in these respects. Vitamin D could not be detected in butterfat samples saved from animals deficient in this factor. Whether or not the fragile bones encountered in one animal and the failure of all the animals to show estrum are directly connected with the lack of vitamin D cannot be established at the present time.