MICROORGANISMS AND HEAT PRODUCTION IN SILAGE 



FERMENTATION 



By O. W. Hunter, 



Dairy Bacteriologist, Kansas Agricultural Experiment Station 



INTRODUCTION 



Heat formation is characteristic of silage fermentation. The amount 

 of heat liberated varies as affected by different factors. The average 

 temperature limits of fermenting forage in the center of the silo range 

 between 30° and 40° C. This represents the temperature of normal 

 fermenting silage. There is a marked difference in the degree of heat 

 noted between the fermenting forage at the top and center of the silo. 

 The amount of oxj'gen present governs to a large extent the amount 

 of heat formed. More oxygen is present in the surface forage than in 

 the center of the silo, which accounts for the higher temperature at the 

 top of the silo. 



In European countries silage is referred to as sweet or sour silage, the 

 amount of heat produced governing the type of fermentation. Sweet 

 silage results when the temperature rises to 50° C, while sour silage is 

 formed if the temperature does not exceed 40° C. 



PREVIOUS INVESTIGATIONS 



Heat production in fermenting forage has never been satisfactorily 

 explained. While it can not be interpreted from previous investigations 

 that this heating results from the major fermentation processes in silage, 

 it seems highly probable. Investigators differ widely regarding the 

 causative agents concerned in silage ripening. Their conclusions may 

 be briefly summarized as follows: Fermentation processes in silage are 

 due to — 



(i) Intramolecular respiration of the tissue cells. 



(2) Intramolecular respiration of the tissue cells, and microorganisms. 

 The former action is essential, v/hile the latter is of secondary importance. 



(3) Microorganisms. 



Fry (yy and Babcock and Russell (i, 2, 3) support the first hypothesis, 

 contending that heat production results from the activity of the plant 

 cells. Russell (12), Kayser (10, p. 367-390), and Samarani (13) state 

 that intramolecular respiration is the most important, but that certain 

 bacilli exert a secondary action. Wollny (15, p. 444-460) likev/ise 

 believes that heat production is caused by the activity of the plant cells, 

 but that the lactic and acetic acids formed are from the action of bacteria. 



' Reference is made by number to " Literature cited, pp. 82-83. 



Journal of Agricultural Research, Vol. X, No. 2 



Washington, D. C. July 9, 1917 



ip Key No. Kans. — 7 



(75) 



