Whey as the Substratum in Vitamin B 1 Assays

Abstract

To meet the requirements for the other essential substances of the Vitamin B complex in Vitamin B₁ (thiamine) assays, early workers used autoclaved yeast. Because of the uncertainties involved in obtaining a yeast quite free from the vitamin in question, the use of autoclaved whey and autoclaved liver has been advocated since the thiamine in these apparently is more readily destroyed. For these assays it is customary to place the test animals on the basal ration at weaning, hold them until the body stores of B₁ are depleted, manifested by stationary weight, and subsequently for a given specified period add the material to be tested in amounts sufficient for considerably less than the optimum gain. Although theoretically it should be possible to use a test animal for successive assays, in practice it is customary to make only one assay with a given animal. Under these conditions, possible discrepancies in the basal ration may be masked, or the results may be modified by enrichments in the test material. Furthermore, when the basal ration is made up on the percentage basis, the amounts taken will vary with the appetite of the animal. Thus, in certain instances, less than the optimum amount of the other constituents of the Vitamin B complex may be taken. Therefore, to make sure that the basal ration is adequate, several successive assays should be made with the same animal, allowing sufficient time between tests for the animal to become depleted of its B₁ store. This would seem to be important, even though a negative control accompany the assays.

To determine the value of certain basal rations for Vitamin B₁ assays, successive tests have been made with animals fed ad libitum a basal ration consisting of B₁-free casein 20 g, sucrose 62 g, Crisco 10 g, cod liver oil 2 g, and 4 g Hawk and Oser's salt mixture 1 with iron citrate and copper sulphate.