438 PRINCIPLES OF AGRICULTURAL CHEMISTRY 



portion is greater than the gain, and increases as the animal be- 

 comes fatter. 



Temperature of Drinking Water. Water consumed must 

 have its temperature raised to the temperature of the animal 

 body. That, of course, requires heat, the amount required being 

 considerable if the water is cold. For an example, an ox weigh- 

 ing 1,000 pounds requires for maintenance, food having the pro- 

 ductive value of 750 grams fat per day. Such an animal may 

 consume 50 kg. water per day. If this water has the temperature 

 of 5 C. the temperature must be raised to 39, that is, 34, and 

 the heat required is 34 x 50 = 1,700 calories, which is equal to 

 about 190 grams fat. This is about 25 per cent, of the main- 

 tenance ration. Cold drinking water must thus be compensated 

 for by more feed. 



Value of Protein for Maintenance. Proteids alone will main- 

 tain the animal body. The quantity of proteids required is con- 

 siderably in excess of the amount of body proteids oxidized by a 

 starving animal. By experiments on dogs, starved, and then fed 

 on lean meat, it has been found that for 100 parts body proteids 

 oxidized, 369 parts proteids in lean meat must be consumed to 

 maintain equilibrium. 



The proteids in the body are in two forms, circulatory and 

 body proteids. The circulatory proteids are rapidly oxidized, 

 while the body proteids are much more resistant. Thus, the 

 amount of proteids oxidized by a starving animal will depend at 

 first upon the quantity of circulatory proteids in the animal, 

 which in turn depends upon the quantity of proteids previously 

 fed. The quantity of proteids oxidized while an animal is 

 starving, rapidly decreases until it becomes nearly constant. 



The amount of proteids destroyed the first day depends upon 

 the previous ration, but after the fifth day it becomes nearly 

 constant. 



Ammonium acetate, asparagin, and other nitrogenous, non- 

 proteid bodies, have little or no value for maintenance. An 

 animal fed upon them, together with starch, fat, etc., will starve 

 to death for want of proteids. 



