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.

This work aimed to assess microbial inoculants (Lactiplantibacillus plantarum and Lentilactobacillus buchneri), chemical additives (natamycin and hexanoic acid), and their combination on fermentation characteristics and aerobic stability in total mixed ration (TMR) silage. The TMR consisted of 30% water bamboo shell (WBS), 10% alfalfa, 20% rice straw, and 40% concentrate. There were six treatments as follows: (1) deionized water (control, CON). (2) lactic acid bacteria (Lactiplantibacillus plantarum + Lentilactobacillus buchneri; LPB, 1 × 10⁶ cfu/g FW). (3) natamycin (NT, 0.02 g/kg FW). (4) hexanoic acid (HA, 0.02 g/kg FW). (5) lactic acid bacteria + natamycin (SLNT, 0.02 g/kg FW). (6) lactic acid bacteria + hexanoic acid (SLHA, 0.02 g/kg FW). After fermentation, laboratory silos (10 L) were opened to assess fermentation quality, followed by a 6-day aerobic stability test. The results showed that all silages were well fermented with high lactic acid (LA) content, low ammonia nitrogen (NH₃-N), and negligible butyric acid (BA) levels. Among all silages, SLNT silage exhibited the greatest LA, acetic acid (AA) levels, LAB counts, and the lowest pH and NH₃-N. For aerobic stability, all additives significantly (p < 0.05) enhanced aerobic stability, delayed (p < 0.05) the decrease in LA and water-soluble carbohydrates (WSC) and the increase in pH, and significantly (p < 0.05) minimized yeast proliferation. The SLNT silage showed the best aerobic stability, with SLHA, NT, HA, and LPB following. In conclusion, SLNT is recommended as the optimal additive in improving the fermentation quality and aerobic stability of TMR silage, with SLHA, NT, HA, and LPB following.

Silage quality and aerobic stability are the key factors affecting the utilization efficiency of silage feed, and ensiling density stands as the fundamental principle of silage making. The experiment presented here evaluates the effects of ensiling density on the silage quality and aerobic stability of alfalfa silage. In this experiment, alfalfa was harvested, wilted, chopped, and subsequently packed into 10 L laboratory silos. The ensiling densities were set to 800 g/L, 700 g/L, and 600 g/L, respectively, with three replicates in each group. Sampling and analysis were carried out at 45 days of silage and 8 days of aerobic exposure. The results showed that ensiling density significantly (p < 0.05) affected the content of ammonia nitrogen, Flieg score, the counts of yeast, and mold. After 45 days of ensiling, 800 g/L silage had the highest contents of dry matter, water-soluble carbohydrates, crude protein, lactic acid, and total organic acids, and the lowest pH and ammonia nitrogen compared to the 700 g/L and 600 g/L silage (p < 0.05). The Flieg score of 800 g/L silage was higher than those of the 700 g/L and 600 g/L silage. The counts of yeast and mold of 800 g/L silage was significantly lower than those of the 700 g/L and 600 g/L silage. During aerobic exposure, a consistent decrease in lactic acid and an increase in pH were observed among all silages. The aerobic stability of 800 g/L silage (156 h) was significantly higher than that in the 700 g/L (136 h) and 600 g/L silage (111 h). It was suggested that the increasing ensiling density above 800 g/L was an effective method to improve both the silage quality and the aerobic stability of alfalfa silage.

The effects of sorbic acid, ethanol, previously fermented juice and their combined additives on fermentation quality and residual water-soluble carbohydrates (WSC) of napiergrass (Pennisetum purpureum) were herein investigated. There were two experiments in total. The treatments of experiment 1 were as follows: control (no addition); sorbic acid at 0.1%, S; molasses at 1.0%, M; previously fermented juice at 5 mL/kg, P; SP; SM; SPM. The treatments of experiment 2 were as follows: control (no addition); ethanol at 1.5%, E; molasses at 1.0%, M; previously fermented juice at 5 mL/kg, P; EM; EP; EPM. The laboratory silos (10 L) were kept at room temperature (~25 °C), and opened after 120 days of ensiling and the chemical compositions of silage were analyzed. Sorbic acid addition significantly (p < 0.05) decreased the silage pH and increased the residual WSC and lactic acid (LA) contents as compared with control. Ethanol addition decreased pH, acetic acid (AA) and volatile fatty acids (VFAs) contents, and increased the ratio of LA/AA, LA and residual WSC contents. Molasses addition increased ratios of LA/AA and enhanced WSC content used by lactic acid bacteria (LAB). The PFJ addition increased AA and ammonia nitrogen/total nitrogen (AN/TN) and decreased the LA contents. Comparing the fermentation quality among all silages in the present study, the combined additives SM and EM performed best in improving the silage quality of napiergrass.

As the most abundant microbial entities on Earth, viruses established the crucial role in soil, marine and human gut ecosystems, but there remained unexplored on viral community dynamics and host interaction during low pH and high LA anaerobic fermentation environments. In this study, we used metagenomic analysis to compare the bacterial and viral community dynamics, and viral encoded auxiliary metabolic genes (AMGs) during the anaerobic fermentation of alfalfa with natural (AF) and Lactiplantibacillus plantarum (Lp) treatments. The results demonstrated that Lp treatments significantly increased lactic acid accumulation, suppressed ammonium nitrogen production, and shifted viral life strategies. Viruses followed ”kill-the-winner” dynamic with lytic activity dominating early succession in AF treatments, but ”piggyback-the-winner” dynamic in Lp treatments. Viruses to host ratio (VHR) analyses revealed that viruses exerted strong top-down lytic regulation to drive rapid microbial succession in the highly diverse AF treatments. Furthermore, we identified 186 carbohydrates and 196 amino acids viral AMGs. Lp treatments selectively enriched specific viral AMGs (e.g., ttdAB) to optimize carbon utilization and host stress adaptation, compared AF treatments with broadly energy generation and amino acid turnover. Together, our study provided a systematic characterization and theoretical foundation of viral community mediating host niche differentiation and biochemical cycling through the synergistic integration of top-down control and bottom-up horizontal genetic reprogramming during anaerobic fermentation.