Ensiling density has significant importance for the quality and preservation of silage. Appropriate ensiling density could improve the nutritional value, extend the storage time of silage and reduce the risk of mold and spoilage. This work aimed to evaluate the effect of ensiling densities on the fermentation quality and aerobic stability of rice straw. The rice straw was obtained after threshing, then chopped and ensiled into a 10 L laboratory silo with three ensiling densities (high density at 700 g/L, medium density at 600 g/L and low density at 500 g/L). Five silos per density were opened after 3, 5, 7, 14, 30 and 60 days of ensiling, and then, the fermentation quality and aerobic stability were analyzed. During ensiling, high density had the highest lactic acid content, and the lowest pH and ammonia nitrogen. There was no difference (p > 0.05) in the propionic acid, butyric acid and ethanol contents among all silage, and the contents of propionic acid and butyric acid were trace amounts. On day 60 of ensiling, the Flieg’s point of high density and medium density were higher than the low density. During aerobic exposure, the continuous lactic acid decrease and pH increase were observed in all silage. The aerobic bacteria and yeasts count in the high density and medium density were lower than that in the low density. The aerobic stability of the high density (26 h) and the medium density (24 h) were higher than that of the low density (13 h). It was suggested that if the ensiling density is higher than 600 g/L, it could effectively improve the fermentation quality and aerobic stability of rice straw.

The current work aimed to evaluate the effect of ensiling density on the fermentation quality and aerobic stability of Pennisetum giganteum silages. The silage was ensiled in laboratory silos (1 L), and three treatments were designed according to different ensiling densities: (1) low density (LD, 750 kg/m³); (2) medium density (MD, 900 kg/m³); and (3) high density (HD, 1050 kg/m³). During ensiling, the silage was sampled for a fermentation quality analysis. All silages were well preserved, as indicated by the high lactic acid (LA) content and low pH (<4.2). The MD treatment had the highest acetic acid content (24.9 g/kg dry matter) and the HD treatment had the lowest ammonia nitrogen (NH₃-N) content (68.2 g/kg total nitrogen, TN) among all silages after 45 days of ensiling. The aerobic stability of HD, MD, and LD persisted for 51 h, 54 h, and 48 h, respectively. The NH₃-N contents of HD and MD were below 80 g/kg TN during aerobic exposure. These results show that the increase in ensiling density improved the fermentation quality and aerobic stability of Pennisetum giganteum silages.