554 



NUTRITION OF FARM ANIMALS 



formed also show in many cases similar variations. Notwith- 

 standing this, however, the percentage of energy utilized did 

 not vary materially in these instances and there is no indica- 

 tion of any such differences as would be expected according to 

 Chauveau's theory. 



The question has also been investigated directly by Zuntz 

 and his associates in experiments on dogs and on man. In 

 these experiments, the feed consisted as largely as possible of 

 the nutrient to be tested (protein, carbohydrates or fat, respec- 

 tively), so that the body metabolism was largely at its expense. 

 The method of investigation was substantially the same as 

 that which has just been described. The final results for the 

 energy metabolism per kilogram and meter traveled were : 



TABLE 156. COMPARISON OF NUTRIENTS FOR WORK PRODUCTION 



The differences are quite small, while, as Zuntz points out, if 

 2.6 cals. represent the demand for energy per unit of work when 

 carbohydrates are the source it should, according to Chauveau's 

 theory, rise to about 3.68 cals. when the energy is derived ex- 

 clusively from fat. 



Later and more elaborate experiments on man led to the same 

 conclusion. Atwater and Benedict, 1 Benedict and Milner, 2 

 and Benedict and Cathcart 3 also report experiments upon 

 men which, while not regarded as conclusive, indicate a pos- 

 sible slight inferiority of fats but one not at all comparable with 

 that demanded by Chauveau's theory. On the whole, then, 



1 U. S. Dept. of Agric., Office Expt. Stas., Bui. 136 (1903), 182. 



2 U. S. Dept. of Agric., Office Expt. Stas., Bui. 175 (1907), 234. 



3 Muscular Work ; Carnegie Institution of Washington, Publ. No. 187 (1913), 145. 



