This study aimed to evaluate the fermentation quality, bacterial community, and nitrate content of sorghum-sudangrass silage with two ensiling densities [550 kg fresh weight (FW)/m3 (low density, LD) and 650 kg FW/m3 (high density, HD)] stored at two temperatures [10°C (low temperature, LT) and 25°C (normal temperature, NT)] for 60 days. The fermentation parameters, microbial counts, bacterial community, nutritional composition, and nitrate and nitrite levels were assessed. The pH and ammonia nitrogen (N) in all silages were below 4.0 and 80 g/kg total N, respectively. Compared with LT treatments, NT treatments had lower pH and lactic acid (LA) bacteria and yeasts counts and contained higher LA and LA/acetic acid (LA/AA) (p < 0.05). The LT-LD contained more ammonia–N than LT-HD (p < 0.05) and had higher nitrate and lower nitrate degradation than other treatments (p < 0.05). Lactobacillus was the most dominant genus with all treatments (57.2–66.9%). The LA, LA/AA, and abundances of Pantoea, Pseudomonas, and Enterobacter in the silage negatively correlated with nitrate concentration and positively correlated with nitrate degradation (p < 0.05). Moreover, pH and ammonia–N were positively correlated with nitrate concentration and negatively correlated with nitrate degradation (p < 0.05). Overall, all silage had satisfactory fermentation quality, and the silage with HD and NT had better fermentation quality and higher nitrate degradation. The bacterial communities in all silages were dominated by Lactobacillus. The nitrate degradation during the fermentation process might be related to the fermentation quality and the activity of Pantoea, Pseudomonas, and Enterobacter in silage.

This study aimed to evaluate the effects of Bacillus subtilis or Lentilactobacillus buchneri on the fermentation quality, aerobic stability, and bacterial and fungal communities of whole plant corn silage during aerobic exposure. Whole plant corn was harvested at the wax maturity stage, which chopped to a length of approximately 1 cm, and treated with the following: distilled sterile water control, 2.0 × 105 CFU/g of Lentilactobacillus buchneri (LB) or 2.0 × 105 CFU/g of Bacillus subtilis (BS) for 42 days silage. Then, the samples were exposed to air (23–28°C) after opening and sampled at 0, 18 and 60 h, to investigate fermentation quality, bacterial and fungal communities, and aerobic stability. Inoculation with LB or BS increased the pH value, acetic acid, and ammonia nitrogen content of silage (P < 0.05), but it was still far below the threshold of inferior silage, the yield of ethanol was reduced (P < 0.05), and satisfactory fermentation quality was achieved. With the extension of the aerobic exposure time, inoculation with LB or BS prolonged the aerobic stabilization time of silage, attenuated the trend of pH increase during aerobic exposure, and increased the residues of lactic acid and acetic acid. The bacterial and fungal alpha diversity indices gradually declined, and the relative abundance of Basidiomycota and Kazachstania gradually increased. The relative abundance of Weissella and unclassified_f_Enterobacteria was higher and the relative abundance of Kazachstania was lower after inoculation with BS compared to the CK group. According to the correlation analysis, Bacillus and Kazachstania are bacteria and fungi that are more closely related to aerobic spoilage and inoculation with LB or BS could inhibit spoilage. The FUNGuild predictive analysis indicated that the higher relative abundance of fungal parasite-undefined saprotroph in the LB or BS groups at AS2, may account for its good aerobic stability. In conclusion, silage inoculated with LB or BS had better fermentation quality and improved aerobic stability by effectively inhibiting the microorganisms that induce aerobic spoilage.

This study aims to investigate the effects of adding Lactobacillus buchneri (LB), Lactobacillus brevis (LBR) and Bacillus subtilis (BS) on the fermentation quality, nitrate degradation and bacterial community of sorghum-sudangrass silage. The results showed that the addition of LB significantly increased the pH and acetic acid content (p < 0.05), but high-quality silage was obtained. The addition of LBR and BS improved the fermentation quality of sorghum-sudangrass silage. The use of additives reduced the nitrate content in sorghum-sudangrass silage. The LB group increased the release of N2O at 3–7 days of ensiling (p < 0.05), and LBR and BS increased the release of N2O at 1–40 days of ensiling (p < 0.05). On the first day of ensiling, all silages were dominated by Weisslla, over 3 days of ensiling all silages were dominated by Lactobacillus. Acinetobacter, Serratia, Aquabacterium, and unclassified_f_enterobacteriaceae showed significant negative correlations with nitrate degradation during sorghum-sudangrass ensiling (p < 0.05). The BS and LBR groups increased the metabolic abundance of denitrification, dissimilatory nitrate reduction, and assimilatory nitrate reduction (p < 0.05). Overall, the additive ensures the fermentation quality of sorghum-sudangrass silage and promotes the degradation of nitrate by altering the bacterial community.