MAINTENANCE RATIONS 311 



most elaborate made up to that time, gave us the 

 following as the minimum quantities which will satisfy 

 the maintenance needs of mature animals of different 

 weights: 



Digestible organic 

 Approxiinate weight substance from 



of animal Energy average meadow hay 



Pounds Calories , Pounds 



1,000 . 10,740 6.75 



1,100 11,620 7.22 



1,200 . 12,280 7.72 



1,300 13,010 8.18 



1,400 13,720 8.62 



1,600 14,420 9.06 



The researches of Armsby and Fries with the respira- 

 tion calorimeter, in a study of the fasting katabolism of a 

 steer, furnish us data much more reliable than can be 

 seciu-ed in any other way. 



410. Fasting katabolism as a measure of mainte- 

 nance needs. — ^The exact maintenance needs of a given 

 animal are most accurately determined while the animal 

 is fasting. When an animal is receiving no food there is 

 no cessation of the vital activities. In the maintenance of 

 these activities there is necessary a certain amount of 

 protein cleavage and a sufficient oxidation of organic com- 

 pounds to meet the energy needs of the animal. The 

 material that is so used is taken from the body structure, 

 and by determining the metabolic nitrogen excreted, 

 and the gaseous products resulting from oxidation, the 

 exact maintenance needs of the animal are ascertained. 

 This is a determination of the fasting katabolism of the 

 animal body. 



The investigation by Armsby and Fries was conducted 

 with a steer which first was fed daily 3.2 kilograms of 

 timothy hay, an amount not sufficient to maintain the 



