Ensiling characteristics and ruminal degradation of Italian ryegrass and lucerne silages treated with cell wall-degrading enzymes

Two experiments were carried out to investigate the effect of added cell wa ll-degrading enzymes at ensiling on the fermentation and in situ degradatio n of grass and legume silages. Primary growths of Italian ryegrass (Lolium multiflorum Lam) and lucerne (Medicago sativa L) were wilted and ensiled in laboratory-scale silos with or without enzymes. Silages were opened at 2, 5, 15 and 45 days after storage; the fermentation quality and the contents of cell wall components (NDF, ADF, ADL) were determined. The 45 day silages were subjected to in situ incubation experiments, and the kinetics of DM a nd NDF degradation was estimated. The enzyme treatment enhanced the lactic acid production (P < 0.01) and reduced the pH value (P < 0.01) of both Ital ian ryegrass and lucerne silages. The contents of cell wall components, how ever, were not affected by enzymes, except for NDF of Italian ryegrass sila ge. The in situ incubation experiments revealed that added enzymes increase d the rapidly degradable DM (P < 0.01) and appeared to decrease the rate of degradation of DIM and NDF of Italian ryegrass silage. The rapidly degrada ble DM was not altered when lucerne was treated, but the rate of degradatio n of NDF was significantly reduced (P < 0.05). These results suggest that a lthough added cell wall-degrading enzymes could improve the preservation of grass and legume silages, the effects on ruminal degradation may be differ ent according to the herbage treated. Enzymatic hydrolysis during ensilage may be restricted to easily digestible cell walls, leaving relatively less digestible components that would be retained in treated silages. (C) 1999 S ociety of Chemical Industry.