MAINTENANCE THE ENERGY REQUIREMENTS 273 



Even in the case of pure, or nearly pure, nutrients fed to carniv- 

 ora, their maintenance values are less than their content of 

 metabolizable energy. 



365. Feed consumption increases heat production. From 

 a slightly different point of view, the experiment just cited 

 furnishes a good illustration of the important fact that the 

 consumption of feed tends to increase the heat production of 

 the body. This is an observation as old as the time of Lavoi- 

 sier. That investigator observed the oxygen consumption of 

 a man to increase materially (about 37 per cent) after a meal, 

 and a multitude of subsequent experiments by numerous in- 

 vestigators and on various species of animals have fully con- 

 firmed these earlier results, so that the fact of an increased metab- 

 olism consequent on the ingestion of feed is fully established. 

 It is especially to the investigations of Zuntz and his associates l 

 that the demonstration of this fact and the recognition of its 

 significance in relation to the nutritive values of feeding stuffs 

 is due. 



For example, Zuntz and Hageman, 2 on the average of a number of 

 experiments in which the respiratory exchange of a horse shortly 

 before feeding in the morning, shortly after feeding, and some hours 

 later was determined by means of the Zuntz form of the Pettenkofer 

 apparatus (299) , obtained the following results, computed per kilo- 

 gram live weight per minute. 



TABLE 38. HEAT PRODUCTION BY A HORSE 



The same effect has been invariably observed with cattle in experi- 

 ments by Armsby and Fries 3 in which the heat production was deter- 

 mined directly by means of the respiration calorimeter. Thus in an 



1 Compare the writer's Principles of Animal Nutrition, pp. 377-385. 

 2 Landw. Jahrb., 27 (1898), Erganzbd. Ill, 282. 

 3 Jour. Agr. Research, 3 (1915), 435. 



