Abstract
This study was conducted to investigate the effects of different additives on the fermentation quality, nutrient composition, bacterial communities, and metabolic profiles of the silage of hybrid Pennisetum. The experiment was conducted using five treatments, i.e., CK, control group, MA, 1% malic acid of fresh matter (FM) basis, GL, 1% glucose of FM basis, CE, 100 U/g FM cellulase, and BS, 106 cfu/g FM Bacillus subtilis, with six replicates each treatment. After a 120-day fermentation, 30 silage packages were opened for subsequent determination. As a result, all four additives had positive effects on the fermentation quality and nutrient composition of the silage of hybrid Pennisetum. The high-throughput sequencing of V3–V4 regions in 16S rRNA was performed, and results showed that Firmicutes and Proteobacteria were the dominant phyla and that Aquabacterium and Bacillus were the dominant genera. MA, GL, CE, and BS treatment resulted in 129, 21, 25, and 40 differential bacteria, respectively. The four additives upregulated Bacillus smithii but downregulated Lactobacillus rossiae. Metabolic profiles were determined by UHPLC-Q/TOF-MS technology and the differential metabolites caused by the four additives were 47, 13, 47, and 18, respectively. These metabolites played antioxidant, antibacterial, and anti-inflammatory functions and involved in pathways, such as the citrate cycle, carbon fixation in photosynthetic organisms, and glyoxylate and dicarboxylate metabolism. In conclusion, silage additives promoted fermentation quality and nutrient composition by altering bacterial communities and metabolic profiles. This study provided potential biomarkers for the improvement of silage quality.
Highlights
The hybrid Pennisetum (Pennisetum americanum × Pennisetum purpureum), a kind of highstalk perennial plant belonging to the Poaceae family, is a fast-growing and high-yielding agricultural crop widely distributed in south China (Song et al, 2019; Cai et al, 2020)
Cellulase, and B. subtilis reduced the contents of NDF in hybrid Pennisetum silage (HPS) (p < 0.05)
Compared with CK, GL, CE, and BS were observed with increased crude protein (CP) and significantly decreased NDIN and ADIN (p < 0.05)
Summary
The hybrid Pennisetum (Pennisetum americanum × Pennisetum purpureum), a kind of highstalk perennial plant belonging to the Poaceae family, is a fast-growing and high-yielding agricultural crop widely distributed in south China (Song et al, 2019; Cai et al, 2020). The hybrid Pennisetum requires minimum management and can resist adverse conditions, including drought, flood, acid, and salt, and can grow on barren land due to its vigorous root system (Wang Y. et al, 2019). Additives Altered Microflora and Metabolism reported for use as feedstock for biogas and biofuel and as forage and ornamental plant (Wang et al, 2014; Suaisom et al, 2019; Zhao et al, 2019). The hybrid Pennisetum is recognized as a forage grass with high buffer capacity and low WSC content and is difficult to ensile (Shah et al, 2020b). Silage additives, including chemicals, enzymes, and LAB and nonLAB species, appear to be important as they play important roles in improving lactate fermentation, suppressing spoilage microorganisms, enhancing aerobic stability, and reducing nutrient degradation (Muck et al, 2018)
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