Evidence of the Synthesis of Vitamin C by Dairy Cows

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Abstract
The results of early investigations (4, 11, 12) indicated that it was unnecessary to provide a food source of vitamin C in the ration of dairy cows. Consequently little attention was paid to this factor when the ex- perimental rations used in our rather extensive studies of vitamin D in dairy cattle nutrition were initiated. Among other symptoms which devel- oped on the experimental ration were atrophy of the gum tissue and loose- ness of the teeth which suggested a possible vitamin C deficiency. Both incisors and molars were affected. In one case the incisors were extremely loose and could be moved back and forth so the outer ends covered a distance of an inch and a half or so. Upon checking the ration it was found that it was very low in vitamin C as well as in vitamin D. As many of the cows were being kept on this ration for three or four years it seemed advisable to make sure that vitamin C deficiency symptoms were not being encountered as a complicating factor in the vitamin D studies. This possibility was investigated using two different approaches to the problem. EXPERII~IENT I METHODS The first part of the investigation was set up to compare the vitamin C in the blood plasma and milk of the experimental cows with that of other groups receiving increasingly larger amounts of vitamin C. The concen- tration of vitamin C in blood plasma is generally considered to be a good index of the vitamin C reserves and an indication of the state of vitamin C nutrition. A normal concentration of vitamin C in the blood plasma of these experimental cows comparable to that in cows under ordinary herd manage- ment would constitute good evidence that they were not suffering from a vitamin C deficiency. Furthermore, if the amount of vitamin C in their milk was similar to that in the milk from cows on good herd rations including pasture it would add further evidence as to the sufficiency of the vitamin C available to the experimental cows. The cows used for this purpose were grouped as follows: Group 1--Five grade Holstein experimental cows on the ration low in vitamin C. This ration consisted of molasses beet pulp for roughage, and a grain mix made up of ground yellow corn 100 pounds, ground oats 100 pounds, corn gluten
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