MAINTENANCE THE ENERGY REQUIREMENTS 275 

 TABLE 41. HEAT PRODUCTION BY A DOG 



Proteins are especially efficient in stimulating the heat production but 

 fats and carbohydrates produce the same effect although to a much 

 less degree. 



366. The specific dynamic action. The effect of the various 

 nutrients, notably of protein, in raising the heat production of 

 the animal above the fasting level, as in the experiments just 

 cited, has been called by Rubner their specific dynamic action. 

 Kellner l has proposed a different terminology. He divides 

 the metabolizable energy of the feed into thermic and dynamic 

 energy. Thermic energy, equivalent to Rubner's specific 

 dynamic action, signifies that portion of the metabolizable 

 energy which is of value to the organism only as a source 

 of heat. Dynamic energy, equivalent to net energy as denned 

 in a subsequent paragraph (370), on the other hand, is that 

 portion of the metabolizable energy which can be utilized for 

 the performance of the vital functions. 



367. Causes of increased heat production. The consump- 

 tion of feed sets in operation (or increases) a variety of activities 

 not manifested by the fasting organism. 



a. Mechanical Work. A not inconsiderable amount of 

 muscular activity is expended by farm animals and especially 

 by the herbivora in the prehension and mastication of their 

 feed and in moving it through the alimentary canal. Since 

 muscular work involves an expenditure of energy, all' of which, 

 in the case of internal work, finally takes the form of heat (342), 

 the mechanical work of digestion is a considerable factor in 

 increasing the metabolism of farm animals, although Armsby 

 and Fries 2 have presented reasons for believing that peristalsis 



1 Ernahrung landw. Nutzt., 6th Ed., p. 105. 



2 Jour. Agr. Research, 3 (1915), 479. 



