274 



NUTRITION OF FARM ANIMALS 



experiment in which three different amounts of alfalfa hay were fed 

 to the same steer in different periods the results were as follows : 



TABLE 39. HEAT PRODUCTION BY A STEER 



Kellner's respiration experiments on fattening cattle have shown 

 that the same effect is produced when feed is added to a basal ration. 

 Thus when wheat gluten was added to a light fattening ration * the 

 heat production as calculated (329) from the balance of matter was 

 as follows : 



TABLE 40. HEAT PRODUCTION BY AN Ox 



For many years it was taught, in accordance with Rubner's theory 

 of "isodynamic replacement," that with carnivora, and presumably 

 with man, the nutrients were of value in proportion to their content 

 of metabolizable energy. Rubner's own later investigations, 2 how- 

 ever, as well as still more recent ones by Lusk and his associates 

 (367 e) , have shown that what is true of the feeding stuffs consumed by 

 horses and cattle is also true of nearly pure nutrients fed to dogs, viz., 

 that if the experiment be made above the critical temperature for the 

 animal there is in each case an increase in the heat production, so that 

 the metabolizable energy is only partially available for maintenance. 

 Thus the average of two of Rubner's experiments in which lean meat 

 was fed gave the following results as compared with the fasting state : 



1 Landw. Vers. Stat., 53 (1900), 130-131. 



2 Die Gesetze des Energieverbrauchs bei der Ernahrung, 1902. 



