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Evidence of the Synthesis of Vitamin C by Dairy Cows^*

Department of Dairy Husbandry, Agricultural Experiment Station, South Dakota State College, Brookings, So. Dak.

ABSTRACT

1. Dairy cows are not dependent upon a food source of vitamin C. Animals maintained up to three or four years on an experimental ration low in vitamin C showed a concentration of this factor in the blood plasma and milk equal to, or even somewhat higher than, that of some cows receiving larger amounts in normal herd rations which included silage and other cows on pasture receiving an abundance of this factor.
   
2. Six twenty-four-hour vitamin-C-balance trials run on three cows receiving the experimental ration low in vitamin C showed that the outgo of this factor far exceeded the intake even after long periods of time on this ration. The negative balances were greater for cows in heavier milk production. The outgo was relatively large in the feces, next highest in the milk for cows in production, and extremely small in the urine.
   
3. The presence of normal concentrations of vitamin C in the blood plasma and milk of dairy cows after three to four years on experimental rations low in vitamin C, and on which the outgo of this factor has undoubtedly been far in excess of the intake as evidenced by the results of six vitamin-C-balance trials, lends strong support to the hypothesis that dairy cows synthesize vitamin C.
   
4. While the site of the probable synthesis of vitamin C has not been conclusively demonstrated these data suggest that it may be along the gastro-intestinal tract.
   

^* Journal Series No. 167.