232 VETERINARY HYGIENE 



what compression is adopted, and this air is utilized in 

 producing the needful fermentation ; once the oxygen in it 

 is used up in this process, no more should be able to find 

 access. 



The chemical changes occurring in silage, were at one 

 time believed to be such that out of useless material useful 

 fodder resulted. This is not so, and even with sound good 

 food there is a loss as the result of this method of preserva- 

 tion ; the proteids suffer on the whole a reduction, some- 

 times a considerable reduction over the amount originally 

 existing. The amides may be increased, due to some of 

 the i^roteid being converted back ; the fat at times is 

 increased, but more often, perhaps, the increase is not a 

 real one, but due to the formation of lactic and other acids, 

 which are taken up by the analytical process employed in 

 extracting the fat ; finally the carbohydrates are diminished. 



It is calculated that there is an absolute loss of organic 

 substance in silage, amounting to from 15 per cent, to 

 20 per cent, of the dry matter originally contained in it. 

 This loss occurs principally during the first six months, 

 after that time it becomes much less. 



Silage is described as siveet or sour. The former has an 

 aromatic smell, while sour silage has a powerfully un- 

 pleasant odour. These two conditions of silage are pro- 

 duced at will, the question being one of temperature within 

 the silo. At or about 120° F. sweet silage is produced, 

 for the organisms which cause lactic, butyric, and acetic 

 fermentations, are destroyed at this temperature. At a 

 lower temperature sour silage is formed by the production 

 of the acids above mentioned. 



If the silo be filled slowly the temperature of the mass 

 can be raised, while if it be quickly filled and closed, the 

 lower temperature favourable for sour silage results. 



Sour silage produces a more succulent food, and is 

 generally preferred by animals. 



If the temperature in the silo rises above 160° E., the 

 fodder gets burned, it turns very brown, loses a great deal 

 of its proteid substances, and becomes indigestible. 



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