Altering the bacterial community: sour soup decreased CO2 production and improved the fermentation quality of Broussonetia papyrifera, Tritriale and mixed silages

Abstract

Introduction: Carbon dioxide (CO₂) generated during the ensiling process is a source of greenhouse gas emissions and a reason for the loss of nutrients during ensiling.

Methods: Broussonetia papyrifera (B), Tritriale (T) and their mixtures (B7T3, B5T5 and B3T7) were ensiled with sour soup (S) and Lactobacillus acidophilus (LAB) to investigate the effects of additives on silage quality, CO2 production and bacterial communities.

Results: After 45 days of fermentation, the B3T7 treatment resulted in the lowest CO₂ production, a relatively high lactic acid content (pH < 4.2), and relatively high relative abundances of Lactiplantibacillus and Weissella after fermentation; the quality of silage in all the treatments with additives was greater than that in the CK treatment, and the CO₂ content was significantly lower than that in the CK treatment (P < 0.05). In addition, the overall silage quality was better than that of CK after the addition of additives, the CO₂ content was significantly lower (P < 0.05), and adding sour soup resulted in a greater effect than adding LAB. CO₂ production was positively correlated with the relative abundances of Lactococcus, Enterococcus, and Neoscardovia and negatively correlated with the relative abundances of Lactiplantibacillus, Weissella, and Sphingomonas.

Conclusions: In summary, selecting an appropriate proportion of different forages for mixed silage and adding sour soup may be effective ways to improve silage quality and reduce CO₂ production during ensiling.

Keywords: bacterial communities; carbon dioxide; fermentation; silage; sour soup.

Figure 1

Microbial communities in silages after 60 days of ensiling. Bacterial communities are reported at the phylum level (A), the genus level (B) and the relative abundances of Lactiplantibacillus (C) and Weissella (D). CK, Control treatment (devoid of any additives); S, included the application of 6 milliliters per kilogram FW of sour soup; LAB, included the addition of 1 × 10⁶ colony-forming units per gram FW of high-quality Lactobacillus acidophilus; B10T0, obtained by mixing chopped Broussonetia papyrifera and Tritriale at ratios of 100:0; B7T3, obtained by mixing chopped Broussonetia papyrifera and Tritriale at ratios of 70:30; B5T5, obtained by mixing chopped Broussonetia papyrifera and Tritriale at ratios of 50:50; B3T7, obtained by mixing chopped Broussonetia papyrifera and Tritriale at ratios of 30:70; B0T10, obtained by mixing chopped Broussonetia papyrifera and Tritriale at ratios of 0:100.

Figure 2

Pearson analysis between nutrient indices, fermentation indices and CO₂ production and the bacterial community after ensiling. LA, lactic acid; AA, acetic acid; TG, total gas; PA, propionic acid; AN, ammonia nitrogen. This study utilized Pearson correlation coefficients for the heatmap analysis. Red squares indicate a positive correlation (values approaching 1) between taxa and production parameters, while blue squares represent a negative correlation (values approaching−1). Significance is denoted by *P < 0.05, **P < 0.01, and ***P < 0.001, with all P-values adjusted using the FDR method.