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 stopped 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 ’’—thatis, itis the amount 
required simply to maintam the animal when it is domg 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 animal, 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. 
Cattle. Horses. 
Live Tees 
weight. Digestible ances Digestibl aoe 
protein. Sales Brahe value 
0.15 1.70 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 
5 65 7.90 9. 60 
