Some Observations on the Growth of Rats on “Fat-Free” and Fat-Containing Diets.

Abstract

Recently Burr and Burr 1 and McAmis, Anderson, and Mendel 2 have shown that the growth of rats on a diet from which all true fat has been excluded is distinctly inferior to that of rats on a diet which contains some fat, even though the fat used is devoid of vitamin A. Furthermore the health of the animals raised on the fat-free diet also suffers. Burr and Burr 1 believe that the total deprivation of food fat leads to the development of a deficiency disease, the symptoms of which are impaired growth, scaliness of the feet and tail, excessive production of dandruff, with ultimate hematuria and albuminuria, loss in weight, and premature death. In a later paper 3 Burr and Burr state that fat is an essential constituent of the diet because of the inability of rats to synthesize sufficient quantities of the more highly unsaturated fatty acids, specifically linoleic acid, for the maintenance of the normal functioning of the tissue lipids.

In the present paper the author wishes to present a few observations which would seem to have a significant bearing on the question of the rôle of fat in animal nutrition, especially with respect to the theory that linoleic acid and other highly unsaturated fatty acids are essential constituents of the diet. For the most part these observations are purely incidental, having been made on rats raised on various diets in connection with a study of phospholipid metabolism.

In the earlier phase of the work, all rats on experimental diets were raised individually in cages constructed throughout of No. 2 mesh wire screen and raised on 2-inch legs. Without exception, the rats which were being fed on the “fat-free” diet∗ developed a peculiar scaly condition of the tail similar in every respect to that described and illustrated by Burr and Burr.