Ensiling characteristics and aerobic stability of direct-cut and wilted grass silages inoculated with Lactobacillus casei or Lactobacillus buchneri

Two experiments were conducted to study the effects of wilting and inoculating Lactobacillus casei or Lactobacillus buchneri on the fermentation and aerobic stability of grass silages. Chopped Italian ryegrass (IR) and Festulolium (FE) were ensiled with or without wilting and added L casei (>10⁶ cfu g^-1 fresh matter (FM)) or L buchneri (>10⁶ cfu g^-1 FM). Silos were opened after 120 days and microbial counts, fermentation products and aerobic stability were determined. Addition of L casei increased lactic acid and decreased acetic acid and dry matter loss regardless of wilting and forage species. Inoculation of L buchneri decreased lactic acid and increased acetic acid and 1,2-propanediol, while the effects appeared greater in direct-cut than in wilted grass silages. Although 1,2-propanediol accumulated in FE silage, the diol was degraded further to propionic acid and 1-propanol in IR silage. The activity of 1,2-propanediol degradation was lowered when IR was wilted prior to ensiling; 1,2-propanediol remained and the production of propionic acid and 1-propanol was less than one-third of that in direct-cut silage. Regardless of forage species, addition of L buchneri increased dry matter loss compared with the untreated control, whereas the loss was not significant in wilted silages. Ammonia production was increased by L buchneri in direct-cut but not in wilted silages. No heating was observed with or without inoculation in direct-cut IR silage after exposure to air. Other silages were deteriorated when L buchneri was not inoculated, while the spoilage was accelerated when L casei was added to FE.