Lactic acid bacteria metabolism affects the composition of volatile organic compounds (VOCs) in alfalfa silage, which results in differences of odor and quality. The aim of this study was to reveal the effects of commercial Lactobacillus plantarum (CL), screened Lactobacillus plantarum (LP), and screened Pediococcus pentosaceus (PP) on quality, microbial community, and VOCs of alfalfa silage based on volatile metabolomics and metagenomics. The results showed that the LP and PP groups had higher sensory and quality grades, and the dominant bacteria were Lactiplantibacillus plantarum and Pediococcus pentosaceus. The main VOCs in alfalfa silage were terpenoids (25.29%), esters (17.08%), and heterocyclic compounds (14.43%), and esters such as methyl benzoate, ethyl benzoate, and ethyl salicylate were significantly increased in the LP and PP groups (P < 0.05). Correlation analysis showed that terpenoids, esters, and alcohols with aromatic odors were positively correlated with Lactiplantibacillus plantarum and Pediococcus pentosaceus. Microbial functions in carbohydrate and amino acid metabolism, biosynthesis of secondary metabolites, and degradation of aromatic compounds were significantly enriched. In conclusion, the addition of lactic acid bacteria can increase the aromatic substances in silage and further improve silage odor and quality.

The objective of this study was to evaluate the effects of Lactiplantibacillus plantarum or cellulase on the fermentation characteristics and bacterial community of mixed alfalfa (Medicago sativa L., AF) and Leymus chinensis (LC) silage. The harvested alfalfa and Leymus chinensis were cut into 1–2 cm lengths by a crop chopper and they were thoroughly mixed at a ratio of 3/2 (wet weight). The mixtures were treated with no addition (CON), Lactiplantibacillus plantarum (LP, 1 × 10⁶ cfu/g fresh material), cellulase (CE, 7.5 × 10² U/kg fresh material) and their combination (LPCE). The forages were packed into triplicate vacuum-sealed, polyethylene bags per treatment and ensiled for 1, 3, 5, 7 and 30 d at room temperature (17–25 °C). Compared to the CON groups, all the additives increased the lactic acid content and decreased the pH and ammonia nitrogen content over the ensiling period. In comparison to the other groups, higher water-soluble carbohydrate contents were discovered in the CE-inoculated silages. Compared to the CON groups, the treatment with LPCE retained the crude protein content and reduced the acid detergent fiber content. The principal coordinate analysis based on the unweighted UniFrac distance showed that individuals in the AF, LC, CON and LPCE treatment could be significantly separated from each other. At the genus level, the bacterial community in the mixed silage involves a shift from Cyanobacteria_unclassified to Lactobacillus. Lactobacillus dominated in all the treatments until the end of the silage, but when added with Lactiplantibacillus plantarum, it was more effective in inhibiting undesirable microorganisms, such as Enterobacter, while reducing microbial diversity. By changing the bacterial community structure after applying Lactiplantibacillus plantarum and cellulase, the mixed silages quality could be further improved. During ensiling, the metabolism of the nucleotide and carbohydrate were enhanced whereas the metabolism of the amino acid, energy, cofactors and vitamins were hindered. In conclusion, the relative abundance of Lactobacillus in the mixed silage increased with the addition of Lactiplantibacillus plantarum and cellulase, which also improved the fermentation quality.

Silage of native grasses can alleviate seasonal forage supply imbalance in pastures and provide additional sources to meet forage demand. The study aimed to investigate the effects of Lactobacillus plantarum (LP), Lactobacillus buchneri (LB), and Lactobacillus plantarum in combination with Lactobacillus buchneri (PB) on the nutritional quality, fermentation quality, and microbial community of native grass silage at 2, 7, 15, and 60 days after ensiling and at 4 and 8 days after aerobic exposure. The results showed that dry matter content, crude protein content, the number of lactic acid bacteria, and lactic acid and acetic acid content increased and pH and ammonia nitrogen content decreased after lactic acid bacteria (LAB) inoculation compared with the control group (CK). LP had the lowest pH and highest lactic acid content but did not have greater aerobic stability. LB maintained a lower pH level and acetic acid remained at a higher level after aerobic exposure; aerobic bacteria, coliform bacteria, yeast, and molds all decreased in number, which effectively improved aerobic stability. The effect of the compound addition of LAB was in between the two other treatments, having higher crude protein content, lactic acid and acetic acid content, lower pH, and ammonia nitrogen content. At the phylum level, the dominant phylum changed from Proteobacteria to Firmicutes after ensiling, and at the genus level, Lactiplantibacillus and Lentilactobacillus were the dominant genera in both LAB added groups, while Limosilactobacillus was the dominant genus in the CK treatment. In conclusion, the addition of LAB can improve native grass silage quality by changing bacterial community structure. LP is beneficial to improve the fermentation quality in the ensiling stage, LB is beneficial to inhibit silage deterioration in the aerobic exposure stage, and compound LAB addition is more beneficial to be applied in native grass silage.

The aim of this study was to evaluate the effects of cellulase (CE) and lactic acid bacteria (LAB) on Caragana korshinskii silage by analyzing the fermentation parameters, chemical composition, and bacterial community. The Caragana korshinskii was harvested at the fruiting period and treated with cellulase and LAB alone as a control treatment with no additive (CK). The ensiling performance and bacterial community were determined after 3, 7, 15, 30, and 60 days of fermentation process. Compared with the CK group, the pH, dry matter loss, and ammonia nitrogen content were significantly (p < 0.05) decreased in the LAB and CE treatments. Compared with the CK and LAB group, the contents of acid detergent fiber, neutral detergent fiber, and acid detergent lignin in the CE group decreased significantly (p < 0.05), and the water-soluble carbohydrates, acetic acid, and lactic acid concentrations increased significantly (p < 0.05). At the genus level of microorganisms, the addition of cellulase and LAB significantly reduced the microbial diversity. Compared with the CK group (78.05%), the relative abundance of Lactiplantibacillus in the CE group (90.19%) and LAB group (88.40%) significantly (p < 0.05) increased. The relative abundance of Pediococcus in the CE group (3.66%) and LAB group (2.14%) was significantly (p < 0.05) lower than that in the CK group (14.73%). Predicted functional profiling of 16S rRNA genes revealed that the addition of cellulase and LAB increased the pyruvate metabolic pathway during Caragana korshinskii silage, thereby increasing the accumulation of lactic acid concentration. The addition of cellulase expressed a better advantage in the biosynthetic capacity of lysine. In summary, the addition of cellulase and LAB could adjust the bacterial community to improve the silage quality of Caragana korshinskii, and the addition of cellulase exhibited better results than the LAB additives.

Most oat forage has low water-soluble carbohydrates (WSC), which may be the main limited factor for silage fermentation safely, but oat is rich in cellulose and hemicellulose; therefore, we assume that xylanase and cellulase as additives can reduce the content of cellulose and xylan in oat silage, increase the microbial fermentable sugar content, and improve the fermentation quality of the silage. After wilting, oats were treated as follows: (i) distributed water (CK); (ii) silages inoculated with xylanase (X); (iii) silages inoculated with cellulase (C), ensiling for 3 days (early stage of silage) and 60 days (late stage of silage), respectively, after ensiling 60 days for a 5-day aerobic exposure study. The pH, neutral detergent fiber (NDF), and acid detergent fiber (ADF) were significantly reduced by xylanase and cellulase treatment during the late stage of silage, and the concentration of lactic acid, acetic acid, and ammonia nitrogen increased remarkably. The WSC content reached its peak with xylanase treatment during the late stage of silage. The content of crude protein (CP) was not affected by additives but by the silage period; CP and ether extract (EE) significantly increased during the late stage of silage compared to the early stage. After ensiling, the bacterial community showed that xylanase and cellulase treatment increased the relative abundance of lactic acid bacteria. Lactobacillus has a higher relative abundance with cellulase treatment after 60 days of ensiling; this can effectively reduce the pH of silage and ensure long-term, stable storage of silage. Cellulase and xylanase increased bacterial diversity during aerobic exposure and improved the aerobic stability of silage significantly. This study indicated that different additives and silage periods had significant effects on chemical compositions, fermentation quality, and bacterial community; meanwhile, both additives improved the aerobic stability of silage. In summary, when the WSC of oat is low, cellulase and xylanase have good effects as silage additives, and the comprehensive effect of cellulase is more prominent.

L. indica L. cv. Mengzao, a medicinal plant of the Ixeris genus, is rich in flavonoids. In order to thoroughly analyze the the distribution and dynamic change of major flavonoids in its various parts from different growth periods, the flavonoids extracted from L. indica L. cv. Mengzao were identified and quantitatively analyzed by ultra-high-performance liquid chromatography mass spectrometer (LC-MS/MS). Results indicated that 15 flavonoids were identified from L. indica L. cv. Mengzao, and rutin, luteolin, luteolin-7-O-glucoside, kaempferol, quercetin, and apigenin are the major flavonoids in L. indica L. cv. Mengzao. In general, the total flavonoids’ content in different parts of L. indica L. cv. Mengzao followed the order flowers > leaves > stems > roots. Flowers and leaves are the main harvesting parts of L. indica L. cv. Mengzao, and the flowering period is the most suitable harvesting period. This study provides valuable information for the development and utilization of L. indica L. cv. Mengzao and determined the best part to harvest and the optimal time for harvesting.