Dynamic Effects and Net Energy Values of Protein, Carbohydrate and Fat

Abstract

The dynamic effects and net energy values of beef muscle protein, dextrin and lard were determined, separately and in combination, by feeding superimposed upon an approximately complete basal diet. The subjects were growing, male, albino rats, and heat was measured by the open-circuit Haldane procedure. The point of view of the experimenters is that even though a nutrient is fed alone it is never utilized alone, and that the combination in which it is metabolized largely determines its dynamic and net energy values. Among the individual supplements the dynamic effect of the beef muscle protein was the highest, that of dextrin was intermediate, and that of lard the lowest; while the dynamic effect of a mixture of the three nutrients was in all cases much lower than would be a value computed from the individual measurements for the three components. Dynamic effects as determined for individual nutrients, therefore, are not significant with reference to combined nutrients. In seven instances among eight the dynamic effects were higher for the 100-gm. than for the 240-gm. rats. The net energy of the beef muscle protein was the lowest because of its low metabolizability and high heat increment; dextrin has a higher net energy value than has beef muscle protein, while the value for lard is much higher still.