Abstract
Types of microorganisms in grass and silages, and their changes during ensilage were discussed mainly based upon the authors' experimental results. Lactic acid bacteria, especially lactobacilli, are found in relatively small numbers on fresh herbage. Provided that sealing of silo is perfect and sufficient amounts of water soluble carbohydrates are available, rapid increase in lactobacilli and concomitant decrease in aerobic Gram-negative bacteria take place in a short period after ensiling. The resulting low pH inhibits the growth of clostridia. Invasion of air into a silo for a certain period after ensiling definitely brings about undesirable fermentation according to the following mechanism: Under the aerobic condition thus induced, active multiplication of Gram-negative bacteria is promoted. As a result, growth of lactobacilli is suppressed therefore pH does not fall satisfactorily. Following the sealing of the silo, Gram-negative bacteria rapidly consume the remaining oxygen and brings about anaerobic condition. Thus the combined high pH and anaerobic conditions promote the growth of clostridia, finally producing silage of very poor quality with large amounts of butyric acid. Inoculation of herbage with Lactobacillus plantarum, combined with glucose addition at ensiling, could overcome the adverse effect of the air invasion and produce high quality silage. Types and behaviour of yeasts and fungi, which are responsible for aerobic deterioration of silages after opening silo, were also described.
