SEVENTEENTH ANNUAL YEAR BOOK— PART VIII 467 



acid formed. About one-half of the sugar present is ordinary cane 

 sugar. This is first broken up into simpler sugars, such as glucose, 

 and then the simple sugars are changed into alcohol and acid. 



Other recent experiments show that the amount of simple sugars in 

 the silage is at first increased by the breaking up of some of the. starch; 

 but the total amount of sugar present, after fermentation is over, is 

 much less than in the green plant material. Sometimes practically all 

 the sugar is used up. The amount of sugar in the green plant, and, 

 therefore, the amount of acid in the silage, depend upon the maturity 

 of the plant when harvested. The amount of sugar in the plant de- 

 creases as the plant approaches maturity. 



Another characteristic change is the breaking down or digestion of 

 protein matter, or the flesh-building constituent of foods. This merely 

 anticipates some of the digestive processes in the alimentary tract of 

 the animal which eats the silage, and therefore does no harm, since little 

 or no nutritive value is lost. 



THE CHANGES COME RAriDLY. 



These various changes take place wath the greatest rapidity during the 

 first five days, and are practically complete at the end of 10 or 12 days. 

 The writer measured the amount of carbonic acid gas produced in several 

 instances, and found that the rate at which the gas was produced was al- 

 ways greatest during the first 24 hours after the corn was put into the 

 silo. The development of heat at the surface of the silage and some 

 of the changes in the sugar are generally most rapid in the first day or 

 two, while the formation of acid is often more rapid somewhat later, 

 or during the second, third, and fourth days. After the fermentative 

 changes which have just been described are finished, or after the first 

 two weeks, there is practically no further change in the silage. Silage 

 has been kept for years in a tight silo without losing either its palatabil- 

 ity or its value. 



The losses which occur during the fermentation process are apprecia- 

 ble, but can be greatly reduced by taking proper precautions, especially 

 by making the silo absolutely tight, including the bottom, and by cover- 

 ing the top with well-packed straw, stover, or other materials. These 

 losses are more than made up for by the incl'eased efficiency of the 

 feed. 



THE CAUSE OF SLLAGE FERMENTATION. 



Ever since silage was first made, there has been doubt about the 

 causes of these important preservative changes in the fermentation of 

 silage. At first, bacteria were thought to be responsible, as in the case 

 of vinegar. Later, other investigators claimed that the cells of the 

 plant itself carried chemical substances called enzymes,* which were 

 the only agents actually concerned. Other writers have taken one side 

 or the other on the subject. 



♦Enzymes are substances produced by living cells of plants and ani- 

 mals, which carry on the life processes of the plant or animal. For ex- 

 ample, enzymes in the stomach and intestines of animals digest its food, 

 and enzymes in the corn plant cause it to grow. 



