USES OF FEED BY ANIMALS FEEDING STANDARDS 45 



digestible carbohydrates,, and 0.1 pound digestible fat per 1000 

 pounds body weight (7.3 pounds digestible carbohydrates and fat). 

 Of late years the amount of net energy which different feed 

 components and feeding stuffs supply is generally taken to repre- 

 sent their value for feeding purposes!. The maintenance require- 

 ments of different animals per thousand pounds or one hundred 

 pounds body weight formulated by Armsby are as follows 1 : 



Maintenance Requirements, According to Armsby 



* Illinois Bulletin 163. The amount of digestible protein is crude, and not true protein 

 (p. 11). 



The figures given for the amounts of digestible protein and 

 energy values for maintaining swine at an even weight are derived 

 from 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), tem- 

 perament, external conditions tending to affect the degree of 

 muscular activity, condition or amount of fat tissue carried, and 

 external temperatures. 2 It is believed, however, that the feeding 

 standards show with a considerable degree of accuracy the average 

 amount 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(Wir) 8 or l-48 pounds, and a 1600- 

 pound cow, 12.7 pounds. 



Feeding for Production. Under ordinary farm conditions, 

 animals are supplied with sufficient feed to more than cover the 



1 Farmers' Bulletin 346 ; U. S. Dept. Agr. Bui. 459. 



8 Pennsylvania Bulletin 111; Mo. Res. Bui. 18. , ; - 



