Chemical and Bacteriological Changes in Grass Silage during the Early Stages of Fermentation I. Chemical Changes

Abstract

Important differences were observed between aerated and sealed silages examined in this study. Aerated silages showed high temperatures and generally poorer quality than the sealed silages. The sealed silages which were tramped and weighted gave few temperature increases. Chemical composition of the silages usually varied according to treatment. In the poorer aerated silages high pH values were observed, along with increased amounts of butyric acid and ammonia nitrogen. Lactic acid always decreased as the fermentation progressed. The rate and development of organic acids could not be correlated with the treatment of the forages. Some silages contained a small amount of acid after 24 hr and others practically none. Most of the acids formed were observed after the most active period of bacterial growth and when the sugar was depleted. The initial levels of sugars in the forages appeared to have little effect on the amount of acids formed in the silages. The total acids were higher in sealed than aerated, which suggested that some of the substrate initially present was destroyed as a result of aeration. High levels of sugars did not ensure silage of superior quality unless the forage was properly ensiled. Since considerably more acids were formed than could be accounted for by the initial sugar content, it was suggested that other substrates are available and utilized by silage bacteria as a source of energy when the sugar is depleted. Among these were included the hemicellulose fraction of plants and plant acids. © 1962, American Dairy Science Association. All rights reserved.