USES OF FEED BY ANIMALS : 35 
feed components and feeding stuffs supply is generally taken to 
represent their value for feeding purposes, as will be shown pres- 
ently (p. 44). This has come largely through the studies of Stoh- 
mann, Rubner, and Kellner in Germany, and Armsby in this 
country. 
The maintenance rations for different animals per thousand 
pounds or one hundred pounds body weight formulated by Armsby 
are as follows:! 
Armsby Standard Maintenance Rations 
Digestible true Energy value, 
Live weight . protein therms 
Cathe nica Rabari enka 1000 pounds 
0.50 pound 6.0 
Horse iss shot iss aes aes 1000 pounds 1.00 pound 7.0 
Sheep see cee. ce cass ov ws 100 pounds 0.10 pound 1.0 
Swine? ose. caseecwe das 100 pounds 0.10 pound 1.12 
ie ip Bulletin 163. The amount of digestible protein is crude, and not true protein 
The figures given for the amounts of digestible protein and 
energy values for maintaining swine at an even weight are derived 
from recent investigations by Professor Wm. Dietrich, formerly of 
the Illinois Experiment Station. 
There are a number of factors that influence the maintenance 
requirements of animals; among these may be mentioned: The 
muscular activity of the animals (whether standing or lying), 
temperament, external conditions tending to affect the degree of 
muscular activity, condition or amount of fat tissue carried, and 
external temperatures.” It is believed, however, that the feeding 
standards show with a considerable degree of accuracy the average 
amounts of digestible true protein and energy values required by 
the different classes of farm animals given for the maintenance of 
an even body weight. 
It is generally assumed that the maintenance requirements of animals 
are proportional to their live weights; i.e., a cow weighing 1200 pounds will 
require 50 per cent more feed for. the maintenance of her body weight than 
an 800-pound cow. This is not correct, however, although sufficiently so for 
most practical purposes. ‘The maintenance requirements increase with the 
surface of the animal, and this is approximately proportional to the squares 
of the cube-roots of the weights of similar animals. If a cow weighing 800 
pounds requires, say, 8 pounds of digestible nutrients for maintenance, a 
1200-pound cow would require 8 X V (4229)2 or 10.48 pounds, and a 1600-pound 
cow, 12.7 pounds. 
1 Farmers’ Bulletin 346, 
? Pennsylvania Bulletin 111. 
