EFFECTS OF PLANT CELL-WALL-DEGRADING ENZYMES AND LACTIC-ACID BACTERIA ON SILAGE FERMENTATION AND COMPOSITION

We investigated the effect of cell-wall-degrading enzymes and a bacterial inoculant on silage fermentation and composition. Under optimal conditions (pH 4.5 and 50-degrees-C for 7 d), high levels of a cellulase enzyme complex from Trichoderma reesei hydrolyzed more than 65% of a purified cellulose source. Growth of Lactobacillus plantarum in minimal medium with cellulose as the major carbon source also was stimulated by the inclusion of a cellulase enzyme complex. Wilted alfalfa (full bloom, 43% DM) was untreated or treated with either a bacterial inoculant (1 x 10(5) lactic acid bacteria/g of forage), cellulase and pectinase enzyme complex (1, 5, and 50 times a recommended dose; the 1 times dose was .6 filter paper units of cellulase and .02 apple pomace units of pectinase/454 g of forage), or combinations of the inoculant and enzyme complex. Microbial inoculation improved fermentation, but the cell-wall-degrading enzyme complex did not. The enzyme complex did not affect NDF or ADF contents relative to untreated silage. A high dose of cellulase (500 times the commercial dose) solubilized about 7% of alfalfa forage NDF (unensiled) under in vitro conditions (pH 4.5 and 50-degrees-C for 50 d). A cellulase enzyme complex (0, 5, and 50 times the commercial dose) was added to direct-cut (20% DM) or wilted (43% DM) alfalfa silage. The 50-fold level of cellulase caused reductions in final silage pH in direct-cut and wilted silage, the reduction being greatest in direct-cut silage. Reductions in NDF and ADF content were small.