The Specific Dynamic Effects of Proteins When Added in Different Amounts to a Maintenance Ration

Abstract

The specific dynamic effects of dried heart muscle, casein and gelatin were determined with rats when each of these protein materials was given as a supplement to a basal maintenance ration in quantities of 1.5 gm. and 3.0 gm. per day, the heat production of the animals while on the maintenance ration being used as the base value. Of the three protein supplements tested casein showed the greatest and heart muscle showed the smallest dynamic effect when this was expressed either as total calories or as a percentage of the metabolizable energy. Accordingly, the net energy value of heart muscle was the greatest and that of casein was the smallest. An inverse relation was observed between the nitrogen retention in the body, caused by the protein supplements, and their dynamic effects expressed as percentages of their metabolizable energy. The results support Rubner's belief that deposited protein has little, if any, specific dynamic effect. No significant differences were observed between the specific dynamic values of the proteins when fed in the different quantities. The net energy values of the protein supplements were practically identical at the two different planes of feeding. The results indicate that the specific dynamic effects of proteins may be satisfactorily determined within a certain range above the maintenance plane of nutrition with the heat production of energy and nitrogen equilibrium as the base value.