Vitamin K and Prothrombin Levels with Special Reference to the Influence of Age

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Abstract
Young White Leghorn chicks require 1.0 to 2.0 μg. of 2-methyl-1, 4-naphthoquinone per day to maintain the prothrombin at a normal level. Only about one-twentieth of this amount, however, is necessary to maintain sufficient prothrombin in the blood to protect the animal from hemorrhagic manifestations. Thus, there is a wide range between the amount of vitamin which will support normal prothrombin levels and the amount necessary for protection from hemorrhage. There is no increase in the amount of vitamin K needed by the young chick as the animal increases in age, despite the fact that the body weight increases severalfold within a few weeks. The data suggest that a large portion of the vitamin needed by the growing animal is associated with the increase in size.