THE PRODUCTION VALUES OF FEEDING STUFFS 657 



758. Experiments on the horse. No experiments on this 

 animal have been reported in which the energy expenditure due 

 to the consumption of a single feeding stuff has been deter- 

 mined. Practically the only data available are those derived 

 from the extensive investigations of Zuntz and Hagemann, the 

 results of which regarding the fasting katabolism have been 

 considered in Chapter VIII (385). On the basis of their ex- 

 periments they compute the energy expenditure and the net 

 energy value from the composition and digestibility of the 

 ration by a method identical in principle with that employed 

 in the experiments on cattle already described. The experi- 

 ments were conducted so differently, however, as to consti- 

 tute practically a distinct method and they may be more 

 conveniently considered in connection with the computation of 

 net energy values discussed in subsequent paragraphs (775-778) . 



759. Results on carnivora. Mention was made in Chapter VIII 

 (365, 366) of the fact that in carnivora, as well as in herbivora and 

 omnivora, the consumption of feed stimulates the heat production, 

 the increase having been called by Rubner the specific dynamic 

 action. It is evident that experiments like those of Rubner and 

 of Lusk were virtually determinations of net energy values for these 

 species. While having no direct bearing on the question of the nutri- 

 tive values of feeding stuffs for farm animals, these data have been 

 extensively quoted in related physiological writings and it seems de- 

 sirable to include them here. Rubner's later experiments were made 

 at about 33 C., or considerably above the critical temperature for 

 the dog, a fact which is of importance in the interpretation of the 

 results (395-397). 



A balance experiment with a respiration calorimeter in which 

 nearly enough fat was fed to supply the requirement for energy gave 



TABLE 199. INCREMENT OF HEAT PRODUCTION BY DOG ON FAT DIET 



2 U 



