PRESERVATION OF FORAGE 39 



31. Silage. Silage is made by the natural fermen- 

 tation of green fodder in receptacles from which the 

 access of air is excluded. In some form this process has 

 been employed over a century. Originally pits in the 

 earth either lined or unlined were used, and such are 

 still employed, but in recent times specially constructed 

 buildings called silos have become common. These may 

 be built of wood, brick, tile, concrete, or steel. Most 

 commonly they are cylindrical in form, and much taller 

 than broad. (Silage is sometimes called ensilage ; but this 

 word is properly a verb meaning to place material in the 

 silo, or to make silage, as to ensilage corn. The verb is 

 sometimes shortened, in the vernacular, to ensile.) 



The proper fermentation requires only the exclusion of 

 air, but practically this is best secured by close packing. 

 Usually this is promoted by cutting the fodder fine and 

 often by trampling and the use of weights. The cut 

 fodder also has the advantage of being more easily re- 

 moved from the silo when used. The volume decreases as 

 fermentation proceeds, so provision must be made for even 

 settling. 



The fermentation results in the formation of various 

 acids and the loss of some substance as gas. While fer- 

 menting, a considerable degree of heat is engendered. 

 The fermentation is complete in from two to eight weeks, 

 but corn silage is as a rule ready for use in four weeks. 

 In contact with air silage decays, due to the attacks of 

 fungi and aerobic bacteria. 



To provide the necessary conditions silos are con- 

 structed with air-tight walls smooth on the inside, and 

 the fodder is cut small so as to pack closely and settle 

 evenly. In filling a silo, the top should not be left ex- 

 posed more than a day or two, as decay then ensues. 



