This experiment was carried out to evaluate the effects of adding fast-sile (FS), previous fermented juice (PFJ), sucrose (S) or fast-sile + sucrose (FS + S) on the fermentation characteristics and carbohydrates fractions of alfalfa silages by the Cornell net carbohydrates and proteins systems (CNCPS). Silages quality were well preserved determined by pH, lactic acid (LA), acetic acid (AA), propionic acid (PA), butyric acid (BA) and (NH3-N, % of TN). Except for the silage with no addition of (CK), all other silages were well preserved. FS + S addition showed the lowest pH and contents of AA, PA, BA, and the highest contents of LA. The contents of WSC (Water soluble carbohydrate) in all alfalfa silages decreased with the extension of ensiling time, especially in the former 15 days and decreased sharply in the first 2 days. The content of sucrose in all alfalfa silages in the residual mono and disaccharides was highest, and the content of fructose was the least. The contents of all these sugars decreased sharply in the first 2 days. The content of hemicellulose decreased during ensiling, while no obvious change on content of cellulose. The content of ADL (acid detergent lignin) in alfalfa silages increased during ensiling. The content of starch in silages reduced rapidly in the former days, and then had not obvious change.Key words: Carbohydrate fractions, alfalfa silage, additives, water soluble carbohydrate (WSC)
