MAINTENANCE EATIONS OF CATTLE. 



39 



method of computation above outlined may probably be assumed to 

 give a fair approach to the truth and is at any rate the only one 

 available. 



THE MAINTENANCE EATIONS OF FARM ANIMALS. 



In endeavoring to formulate the maintenance rations of farm 

 animals it is important to have a clear conception of the nature of 

 the problem and to distinguish between its physiological and its 

 economic aspects. The physiological conception of the maintenance 

 requirement is the amount of energy required to carry on the abso- 

 lutely necessary vital processes in a state of the most complete rest 

 possible. It is the least amount on which life can be sustained; 

 the physiological minimum ; the base line for comparison. In actual 

 practice, no such state of complete rest can be maintained for any 

 length of time. There is necessarily superadded to the minimum 

 physiological requirement the energy expended in a variety of ways, 

 but especially in the numerous minor muscular movements which are 

 unavoidable in the waking state, which may be summarized under 

 the term incidental work. Some of the factors of this incidental 

 work are discussed on subsequent pages. Physiologically, this addi- 

 tional energy is expended for production; the animal is doing work 

 on its surroundings. Economically, however, the work done is of 

 no value and the energy required to do it is, therefore, from that 

 point of view, a part of the cost of maintenance. In practice, of 

 course, it is not the physiological but the economic requirement which 

 is of importance. The latter will neeessarity be more or less variable 

 according to the individuality of the animal and the conditions 

 under which it is maintained, as will appear in the following dis- 

 cussion, and statements of maintenance requirements and rations 

 should therefore indicate to such a degree as is possible the conditions 

 to which they are intended to apply. 



CATTLE. 



The maintenance requirements of cattle have been more exten- 

 sively studied than those of other species and it will be convenient 

 to take them up first, using the data also as a means of illustrating 

 the principles involved and the methods of investigation employed. 



The estimate of the maintenance ration of cattle long current 

 and still occasionally cited was based upon the investigations of 

 Henneberg and Stohmann 1 in 1858. According to their results, a 

 1,000-pound steer required for maintenance about 8.16 pounds of 

 digestible organic matter per day, equivalent to about 14.3 therms 

 of metabolizable energy. In view of the rather high stable tem- 



1 Beitriige zur Begriindung einer i"ationellen Futterung der Wiederkauer, Heft I, 

 pp. 17-188. 



