201 



in the original material, the conditions of weather, the construction 

 of the silo, the treatment and the ferments concerned make silage a 

 very variable product and great care and much linowk'dge is needed 

 to secure uniformly good sihige. 



Kinds of fci-nioitx. — The kinds of ferments which cause changes in 

 the silo are numerous and as 3^et not sufficiently understood. They 

 include (1) yeasts, whicli cause ah'oliolic and other fermentations; 

 (2) bacteria, which cause the foi-mation of acids and the heating in 

 the silo and appear to aid in (he destructive changes, notably the 

 semij^utrid decomposition, accomi^anied by bad odors, which so often 

 occurs in old silage; {?>) molds, which also cause putrefaction. 



Alcoholic fermentation in silage — Yeasts. — It is doubtful if alco- 

 hol occui's in silage. If it does it is not ethyl alcohol — the compound 

 to which ill couHuon usage the name alcohol is applied — but butyl 

 alcohol or some allied form, and the fermentation which it produces 

 is due not to yeast but to bacteria. Yeast is at no time found in the 

 silo as a producer of alcohol. The species which does occur, often in 

 considerable (luantity. is not the familiar balcer's or brewer's yeast, 

 but another species, the Sac-haroirnjces mycoderma^ Rees, or Myco- 

 dcrma rini of Pasteur. This does not produce alcohol, except to a 

 limited exterit under special conditions not known to exist in the silo. 

 It is therefore not true, as has been claimed, that the so-called 

 '' sweet silage "" is the result of an alcoholic fermentation. 



Hot silage. — The hot fermentation which often takes place soon 

 after the silo is filled is not explained fully b}' the facts at hand and 

 demands much study. It is not due to yeast. The yeasts can not 

 retain their activity at anything like the temperature attained, which 

 reac-hes (;0° C (140° F.) or higher. Above 30° C yeast loses its 

 lH)wer of growth and development in an accelerating ratio as the 

 lieat iucreases. The high teiiiperature seems to be due to two or more 

 species of bacteria (rod-like bacilli) similar to those which appear to 

 cause butyric and like forms of fermentation. At least two species 

 were found. They thrive in newly filled silos at temperatures from 

 (■«0° to 70° C. These organisms are found in hot silage and in equally 

 hot uuuuire piles. They are anau'obic, that is to say, they do not need 

 free oxygen, or, in other words, they do not require air for life. Still 

 thev do not seem to cause the very high temperature often found in 

 the >ilo without a partial supply of air. The high temperature 

 occurring shortly after the material is put in the silo does not destroy 

 the bactiM-ia and molds which later cause acid fermentation and 

 putrefaction. After the heating, however, the silage settles and the 

 air is excluded. The initial high temperature wiiich these bacteria 

 induce is therefore probably most serviceable by causing this closer 

 l)acking of the silage and the exclusion of the air. rather than by 

 killiuir till' gei-ms of other ferments. 



