SILOS AND SILAGE 



249 



are the same materials dried. A German experiment 1 showed 

 that the horse expended one third more energy in chewing hay 

 than was required to masticate similar foodstuffs in a green 

 state. This is one reason why stock do so much better on 

 pastures than on hay. Another important reason is that the 

 stock relish green feed 

 better than cured feed, 

 and therefore eat more. 

 323. How silage 

 keeps. It was difficult 

 at first to make people 

 believe that a green 

 material like corn or 

 sorghum would keep in 

 a silo when they knew 

 it would decay if thrown 

 into a pile in the open 

 air. But a silo is almost 

 air-tight (Fig. 118), 

 and, after the silage 

 has settled, little air 

 reaches it. Excluding 

 most of the air, how- 

 ever, is not the only con- 

 dition necessary to the 

 preservation of silage. 

 A certain amount of 

 acid must be present to 



preserve or pickle the feed. While there are a number of 

 acids produced in silage, there are only two with which we are 

 particularly concerned lactic acid, the principal acid of sour 

 milk ; and acetic acid, the principal acid of vinegar. These 

 acids preserve the silage in much the same way that vinegar 

 preserves pickles. To produce these acids there must be pres- 

 ent in the materials put into the silo either sugar or substances 



1 Kellner, The Scientific Feeding of Animals, p. 88. 



FIG. 118. Two types of cylindrical silos 



The silo at the left is constructed of cement and was 



built inside of forms. The silo at the right is made 



of wooden staves held in place by iron rods 



