Observations on the Nutritive Value of Certain Fats.

In connection with experiments concerned with the growth of rats on low-fat diets, observations have been made which emphasize the nutritive value of certain fats, and illustrate the marked variance in the results obtained in different laboratories with a fat such as cod liver oil. The basal diet introduced by Burr 1 (purified casein —25, commercial sucrose —75, modified Osborne and Mendel salt mixture —4) was used and was supplemented daily with 0.5 gm. of whole dried yeast and 9 drops of cod liver oil unless stated otherwise. On this diet male rats, 4 weeks of age, increased in weight to 200 gm. in approximately 60 days. These rats (Group 1) exhibited feet and tail signs apparently indentical with those noted by Burr and Burr 2 , 3 in rats on a fat-free diet. The more serious effects reported by these authors were not evident in our experiments, possibly because we used whole yeast in place of ether-extracted yeast and cod liver oil in place of the non-saponifiable fraction of that oil. The feet and tail signs were not prevented by doubling the daily yeast supplement (Group 7), or by adding an active extract of rice polishings (Group 10) or by adding an active extract of liver (Group 8). The signs were, for the most part, prevented by wheat germ oil (Group 4), lard (Group 6), and whole liver (Group 9). Wheat germ oil was most effective, and lard was least effective, although the effect of the lard was greater when the daily supplement of cod liver oil was decreased (Group 5). The severity of the condition of the tails of the rats given 12 drops of cod liver oil daily was even worse than that of the animals given 9 drops daily.