Microbial Activities in Alfalfa and Orchard Grass Ensiled Under Certain Conditions in Experimental Silos

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Abstract
Numbers of micro-organisms, utilization of plant sugars, pH, and production of ammonia were the primary measures of microbial activity. Differential media and studies of bacterial cultures also provided information on differences in microbial activity as it occurred in ensiled high moisture and wilted forages and as affected by sealing the silo and addition of sulfur dioxide. The predominant chromogenic and coliform bacteria on the forage were rapidly replaced by various lactic acid bacteria after ensiling. Lactic acid bacteria were associated with the greatest microbial activity and acid production early in the storage period and their growth were enhanced in forage high in sugar and moisture. Late in the storage period secondary activity occurred in high moisture silages deficient in plant sugars. Forages low in moisture such as caused by wilting reduced and prolonged microbial activity but wilting was advantageous as was sulfur dioxide in checking continued activity and the secondary fermentation. Sealing the silo accentuated growth of lactic acid bacteria, acid production, and prevented top spoilage. Results indicated that controlled fermentation requires either a proper balance between moisture and carbohydrate such as by wilting of forages low in sugar and high in moisture or the use of additives selective against destructive bacterial activity.