Cumulative Effects on Protein Utilization of Highly Milled and Whole Wheat Flours

When digestibility of food constituents is determined by the conventional method the experiment is of such short duration that only acute effects of the food on the animal have time to appear. Chronic effects are absent. Tests already reported 1 show that the habitual use by white rats of a ration consisting of white flour, potatoes, lean beef, milk, fats, and salts in the proportions customary for human dietaries, resulted, after several months, in a protein utilization somewhat lower than that found for a similar ration but containing whole wheat meal instead of white flour. Since white flour has been found to be more digestible than wheat meal 2 it seemed probable that a change gradually develops in the condition of the animal as a result of the continued use of the dietaries whereby digestion becomes less effective on the white flour ration or more effective on the wheat meal ration. To test these ideas digestion trials were made, at intervals, upon the same animals, maintained upon rations which varied only in the kind of flour used or in the amount of fiber or of yeast.

Five rations were compared. Ration I contained, white flour 45.5, dried potatoes 13.7, dried beef 11.9, sucrose 11.2, butter 5.2, lard 5.1, dried skim milk 4.7, and salt mixture 2.7. The crude fiber content of this ration is about 0.8%, protein 16.5%, and fat 12.0%. Presumably it is deficient in the antineuritic vitamin. Ration II contained enough ground filter paper to raise its fiber content to about 3.0%, otherwise it was like Ration I. Ration III contained both filter paper and 4.4% of dried brewers' yeast. Ration IV contained brewers' yeast but no paper. Ration V contained wheat meal in place of the white flour of Ration I.