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The Influence of High Levels of Fat with Suboptimum Levels of Riboflavin on the Growth of Chicks¹

Three Figures

Department of Biochemistry and Nutrition, Texas Agricultural Experiment Station, College Station

Chicks receiving moderately high levels of refined cottonseed oil in diets low in riboflavin cease growing much sooner than those on a similar diet that contains no added fat. When 4 µg of riboflavin per gram of feed are added to the diets, the growth response is essentially the same irrespective of whether the diets contain fat. Lard did not retard the rate of growth, nor did a commercial hydrogenated vegetable fat.⁵ The response to cottonseed oil does not appear to be due to the development of rancidity since means were taken to prevent its formation, including the addition of anti-oxidants and refrigeration of the feed.

The chemical difference between cottonseed oil on the one hand and lard and hydrogenated vegetable oil on the other is the high concentration of linoleic acid in the former. Since there is no known reason for believing that the unsaturated acids require more riboflavin for their metabolism than the saturated it would seem more probable that the unsaturated acids interfere more with the intestinal synthesis of riboflavin.

The alternative possibility, however, must still be considered. Lehninger has recently shown ('48) that cytochrome is an essential constituent of the enzymatic system for the oxidative catabolism of fatty acids. Since riboflavin is a constituent of the enzyme system which catalyzes the reduction of the oxidized form of cytochrome C (Haas, Horecker and Hogness, '40), it becomes apparent that this vitamin has a role in fatty acid catabolism and an increased requirement might be expected on a high fat diet.

⁵ See footnote 4, page 251.

Manuscript received 17 January 1949.