498 



NUTRITION OF FARM ANIMALS 



of the milk would retain a larger percentage of the chemical 

 energy of the digestible matter from which it was formed than 

 would the increase of body tissue which that same digestible 

 matter could produce. 



593. Computation of equivalent net energy values for fat- 

 tening. Let it be assumed that the digestible protein and 

 carbohydrates of the feed may be converted into the corre- 

 sponding compounds of milk without loss and that the expendi- 

 ture of energy in the production of milk fat from carbohydrates 

 is the same as that observed by Kellner (769) for the production 

 of body fat. Then each gram of protein or carbohydrates in 

 the milk would require the supply in the feed of one gram of 

 digestible protein or carbohydrates respectively, while each 

 gram of milk fat if manufactured from carbohydrates would 

 require about 3.9 grams of the latter. 



The corresponding amounts of energy recovered in milk 

 production and in fattening respectively would, according to 

 the foregoing assumptions, be as follows : 



TABLE 136. COMPUTED ENERGY RECOVERED IN MILK PRODUCTION AND 

 IN FATTENING 



On this basis, it is easy to compute approximately the amount 

 of net energy for fattening which would be required for the 

 production of a given amount of milk of known composition. 

 Thus average four per cent milk, according to Table 144 (604), 

 contains 3.08 per cent of protein, 4.85 per cent of carbohy- 

 drates and 4.0 per cent of fat. The actual amount of energy 

 contained in a pound of such milk would be 336 Cals., while 

 the amount of energy which would have been recovered from 

 the same feed if used for fattening would have been only 252 

 Cals. Conversely, an amount of feed containing 252 Cals. of 

 net energy as computed from the results of fattening experi- 



1 Kellner's factors. 



