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Concerning the Alleged Occurrence of an "Animal Protein Factor" Required for the Survival of Young Rats¹

I. Studies with Unpurified Rations

Department of Agricultural Biochemistry, University of Minnesota, Institute of Agriculture, St. Paul

1. For a study of the alleged occurrence of an unrecognized "animal protein factor" required for survival of young rats, the usefulness of rations containing exhaustively leached casein plus a mixture of cereal grains or rolled oats was investigated.

2. When casein was leached for two weeks with 0.5% acetic acid and fed at a 5% level as a component of a vitamin B₁₂-deficient ration containing 82.5% of a mixture of cereal grains, there was an increase in mortality of young rats in successive generations until it reached 100% in the F₃ generation young. Vitamin B₁₂ reduced mortality to about 67%.

3. When similar casein preparations, leached at pH 4.6 or 3.6 were fed at a 6.5% level as components of rations containing 84% rolled oats and other ingredients of synthetic or plant origin, a high preweaning mortality of young rats was not consistently observed through 4 successive generations.

4. These experiments emphasize that specific conditions, as yet only empirically defined, are necessary for establishment of a high preweaning mortality of the young.

Manuscript received 18 October 1954.