SUMMARY. 



On the basis of the results recorded in the foregoing pages, it 

 is believed that the average maintenance ration of thin cattle may 

 be formulated with a considerable degree of accuracy as follows : 



Average maintenance ration of cattle. 

 (per looo Ib. live weight.) 



Digestible crude protein per day. ... 0.5 Ib 

 Energy value per day 6.2 Therms 



FACTORS AFFECTING THE MAINTENANCE REQUIREMENT. 



It is apparent from the foregoing results that while it is pos- 

 sible to state with a considerable degree of accuracy the average 

 maintenance ration of cattle, individual cases may vary considera- 

 bly from the average. It is desirable, therefore, to consider briefly 

 some of the causes of these variations. 



Muscular activity. 



Probably the most important of these factors is muscular activ- 

 ity. All muscular work is done at the expense of energy derived 

 from the oxidation of body material, and no other factor influences 

 so largely the amount of tissue thus used up. In maintenance, of 

 course, an animal does no work in the ordinary sense, but notwith- 

 standing there is necessarily more or less muscular activity which 

 tends to increase the maintenance requirement. 



Standing and lying : One of the most marked examples of the 

 effect of muscular exertion is furnished in the case of cattle by a 

 comparison of the standing and lying positions. In experiments at 

 this Institute it has been observed that a steer when standing has 

 produced from 28 to nearly 65 per cent, more heat than the same 

 steer when lying down, this heat of course arising from the com- 

 bustion of materials of the body or of the feed. Similar results 

 have been obtained elsewhere in experiments upon dogs and some- 

 what less marked ones in experiments upon men. While some ex- 

 perimenters have failed to find with ruminants a correspondingly 

 large increase in the carbon dioxid given off during standing as 

 compared with lying, the general fact that standing increases the 

 heat production is unquestioned. It is clear, then, that of two steers, 

 one of which lies down for 12 hours and the other for 8 hours out 

 of the 24, the former will, other things being equal, require less 



(18) 





