52 



FEEDS AND FEEDING, ABRIDGED 



ever, the greater part of the food is required merely as fuel to keep up 

 the body temperature. Hence, except for the pig, maintenance rations 

 for the larger farm animals may consist largely of cheap roughages, 

 such as hay and straw, which furnish abundant heat but do not yield 

 much net energy. This has great practical importance, for it shoAvs 

 M^hy idle horses and stock cattle can be carried thru the winter on 

 roughage alone, without grain. 



It is commonly assumed in computing rations that the amount of 

 feed required to maintain an animal depends on its body weight. 



Fig. 14. — Heavily-fed Animals Ordinarily Have an Excess of Heat 



Heavily-fed fattening steers thrive best with .no shelter except an open shed, 

 but animals being carried thru the winter on scanty rations need warmer quar- 

 ters. (From Prairie Farmer.) 



Strictly speaking, however, the maintenance requirement depends not 

 on the live weight, but on the body surface. This is due to the fact 

 that the loss of heat from the body is proportional to the body sur- 

 face and not to its weight. A 1,600-lb. steer does not have twice the 

 body surface of" an 800-lb. one, and hence will not require twice as 

 much feed for maintenance. Individual animals of the same kind 

 and size may also differ somewhat in their requirements. For 

 example, a quiet animal uses up less body fuel than a nervous, active 

 one. Due chiefly to increased muscular action, an animal when stand- 



