The Nutrition of the Newborn Dairy Calf. I. Changes in the Tryptophan Content of the Blood Plasma Following Birth and the Ingestion of Colostrum

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Abstract
A study of the tryptophan content of the blood plasma of calves showed average values of 0.46, 0.94, 0.96, 0.86, and 0.81 mg. per g. wet basis for the newborn calf and at 3, 7, 14 and 21 days of age, respectively. The amt. of tryptophan in first-milking colostrum was found to be about 5 times as high and that of the 2d milking about 3 times as high as that of normal milk. These results are discussed in the light of tryptophan being the possible precursor for the in vivo synthesis of nicotinic acid.