284 



NUTRITION OF FARM ANIMALS 



tenance rations would likewise be different, as is shown in the 

 following statement, in which are included for further illustra- 

 tion two mixed rations used by the same experimenters. 



TABLE 43. EXAMPLES or MAINTENANCE RATIONS FOR A IOOO-POUND 



STEER 



By stating the maintenance requirement in terms of net energy 

 a single value is obtained for an animal, or a single average for 

 a class of animals, which is a general expression of its main- 

 tenance requirement irrespective (substantially) of the par- 

 ticular feed or feeds which may be used to satisfy it, while a 

 statement in terms of metabolizable energy or of weight of 

 feed must also specify the particular kind of feed to which it 

 applies. The greater convenience of the former method for 

 the computation of actual rations is evident. To the extent to 

 which the net energy values of feeding stuffs are known or can 

 be estimated it is possible to make up an almost endless variety 

 of combinations which will all be maintenance rations, i.e., 

 will furnish the amount of net energy required by the animal. 



In the following paragraphs, this method of expression will be 

 followed so far as practicable, although unfortunately compara- 

 tively few determinations of the net energy requirements for 

 maintenance have yet been reported except in the case of cattle. 



376. Modified conception of energy requirement. A study 

 of the conditions, especially as regards muscular work, which 

 influence the katabolism of the fasting animal makes it evident 

 that the conception of the energy requirement outlined in 

 Chapter VII requires some modification in its application to 

 the actual feeding of animals. 



As was there shown (344), the heat production of the fasting 

 animal in a state of absolute muscular rest may be regarded as 



