Interaction effect of silo density and additives on the fermentation quality, microbial counts, chemical composition and in vitro degradability of rice straw silage

•As the silo density increased, the quality of rice straw silages improved.•Lactic acid bacteria (LAB) improved fermentation quality of rice straw silages.•Combination of enzymes and LAB and high silo density (>400 kg/m3) reached the best. This research evaluated the effect of molasses (M), cellulosic enzymes (E) and lactic acid bacteria (LAB) alone or in combination (M + LAB and E + LAB) on the fermentation quality, microbial counts, chemical composition and in vitro degradability of rice straw silages in different silo densities (200, 300, 400 and 500 kg/m3). The M or E groups alone increased the dry matter (DM) losses at low silo densities. Acetic acid produced by LAB-related groups significantly inhibited yeast and mould at the silo density of 300 kg/m3. Under high silo densities (>400 kg/m3), LAB-related additives significantly improved the fermentation quality and reduced the DM losses. The use of E + LAB further improved the in vitro degradability of rice straw silages at high silo densities. In conclusion, higher silo density and appropriate complex additives were of great significance to improve the quality of rice straw silage.