14 



BULLETIN 459, U. S. DEPARTMENT OF AGRICULTURE. 



FEED REQUIREMENTS. 



Assuming that the foregoing table represents with a fair degree 

 of accuracy the amount of repair material (protein) on the one hand 

 and of energy on the other which the various feeding stuffs can 

 supply, we still need to know how much of each is required by the 

 bodies of animals of different kinds and kept for different purposes; 

 in other words, we need some formulation of the feed requirements 

 of farm animals. 



REQUIREMENTS FOR MAINTENANCE. 



Since the animal machine may not be stoj)ped when it is not in 

 active use, it requires, as was pointed out on page 4, and as is a 

 familiar fact of experience, a continual supply of feed. This amount 

 of feed, which is required simply to support the animal, is commonly 

 designated as the " maintenance requirement " — that is, it is the amount 

 required simply to maintain the animal when it is doing no work 

 and producing nothing. In other words, it is the least amount on 

 which life can be permanently maintained. 



The maintenance requirement is naturally greater for a large than 

 for a small animal. Experiment has shown, however, that this 

 increase is not proportional to the weight of the annual, but approxi- 

 mately to the amount of surface which it exposes, so that the large 

 animal requires less feed in proportion to its weight to maintain it 

 than does the small one. 



The following tables show the amounts of protein and of net 

 energy required per head for the maintenance of cattle, sheep, and 

 horses of different weights. The figures given for sheep include a 

 sufficient allowance for the normal growth of wool. No very satis- 

 factory figures for swine are available. It should be understood that 

 strict accuracy is not claimed for these figures, although they are sub- 

 stantially correct. In particular there seems to be reason to believe 

 that the maintenance requirement of fattening animals increases 

 somewhat more rapidly than these tables indicate. 



Maintenance requirements of cattle and horses, per day and head. 



Live 



Cattle. 



Horses. 











weight. 



Digestible 

 protein. 



Net 

 energy 

 value. 



Digestible 

 protein. 



Net 

 energy 

 value. 



Pounds. 



Pounds. 



Therms. 



Pounds. 



Therms. 



150 



0.15 



1.70 



0.18 



2.10 



250 



.20 



2.40 



.24 



2.90 



500 



.30 



3.80 



.36 



4,60 



750 



.40 



4.95 



.48 



6.00 



1,000 



.50 



6.00 



.60 



7.30 



1,250 



.60 



7.00 



.72 



8.50 



1,500 



.65 



7. 90 



.78 



9.60 



