Changes in mono-and disaccharides compositions of guineagrass (Panicum maximum Jacq.) silage during early stages of ensiling

The dynamics of fermentation during the early stage of ensiling was studied with guinea-grass (Panicum maximum Jacq.) ensiled in the laboratory silos of 100 ml capacity. The silos were kept in the room set at 25°C, and then were opened on 0.5, 1, 2, 3, 5 and 7 days after ensiling, respectively. The samples were taken from three silos at each sampling time for chemical analyses. The results showed a slow decrease in pH and a slow increase in lactic acid content during the early stage of ensiling. The rate and extent of the full fermentation process was restricted, causing a high final pH value, low contents of lactic acid, acetic acid, total VFAs and total organic acids. No or only small amounts of butyric acid, valeric acid and propionic acid and low values of AN/TN at the end of ensiling implied that the silage was stable. However, there was an evidence that ethanol increased continuously as the major fermentation product and only detected level of residual mono-and disaccharides (fructose, glucose and sucrose) were found at the end of the experiment, indicating that alcoholic fermentation had taken place due to yeasts activity. The contents of mono-and disaccharides showed the largest decreases within the initial 0.5 day of ensiling, however, very low contents of fermentation products were detected, suggesting that the loss was caused mainly by plant respiration in this period. The rate of reduction in mono-and disaccharides compositions within initial 5 days of ensiling was ranked in the order of glucose〉fructose〉sucrose, suggesting that glucose and fructose might be more favorably utilized by microorganisms than sucrose.