Dec. 2, 1908.] Agricultural Gazette of N.S. W. 1019 



The Chemical Chaijges takiijg place durii]g tlje 



Eijsilage of Maize. 



EDWARD J. RUSSELL, D.Sc. (Lond.), 

 Rothamsted Experiment Station. 



When the green parts of living plants are cut up and packed in a loosely 

 covered vessel allowing entrance of air, mould soon makes its appearance and 

 decomposition begins ; the mass becomes alkaline and is ultimately converted 

 into black humic bodies quite unfit for cattle food. But if air is excluded 

 the change is fumlamentally different ; no mould developes, the temperature 

 rises, the mass takes on a greenish -brown colour and characteristic odour, it 

 becomes acid, and for a long period is suitable for cattle food. The former is- 

 a putrefactive change, the latter gives rise to silage. 



The general chemical changes known to take place during ensilage are the 

 conversion of sugar and similar bodies into carbon dioxide and water, the 

 production of volatile acetic and butyric acids and of non-volatile lactic acid,, 

 and the conversion of protein into non-protein^ material. 



Several hypotheses have been put forwai-d to account for the silage 

 changes, and to explain why the product keeps so long. According ta 

 one — perhaps the commonest — fermentations set up by micro-organisms- 

 evolve so much heat that everything is killed and the mass becomes 

 sterilised. Another view is that certain thermophilous organisms bring 

 about the observed changes.- WollnyS considered that the lactic and acetic^ 

 acids were formed by bacteria, but that the rise of temperature was a respira- 

 tion effect. On the other hand, Pasteur's work on anaerobic respiration led 

 Fry* to conclude that the changes are not due to bacteria at all, but to the 

 cell, and are the result of the altered conditions in which the cell now finds- 

 itself. In absence of air oxidation of sugar does not go as far as carbon 

 dioxide and water, but stops at alcohol and acetic acid. This view has been 

 developed by Babcock and H. L. Russell^ in an important paper published 

 in 1902 ; they found that silage could be made perfectly well in the presence 

 of ether or chloroform, and they therefore conclude that bacterial activity 

 cannot be an essential factor in the process. No acid was produced in tins 

 case, however ; but acidity appeared when the cells were not killed, and the- 

 longer the cells lived the more acid was formed. 



'Sometimes called '• amides, " but it is highly desirable that this term should be 

 dropped. The word "amide" lias a definite chemical significance, and many of tlie 

 nitrogenous non-protein bodies in plants are not " amides" but amino-acids, etc. 



- E.g. — Griffiths, Chtm. Xeics, 1894, 70, 273 : see also Lafar, 7VcA. Mijcology, p. 262. 



' Die Zersetzung der Organischen Stojj'e, 1897. 



♦ Su-eet Si/age, 1885, Agric. Press Co., London. 



^ Centr./iir Bakt. 1902, 9, 81. 



