Lactobacillus plantarum Inoculants Delay Spoilage of High Moisture Alfalfa Silages by Regulating Bacterial Community Composition

Abstract

The objective of this study was to investigate the mechanism of Lactobacillus plantarum (L. plantarum) involved in improving fermentation quality of naturally ensiled alfalfa under poor conditions. High-moisture wilted alfalfa was ensiled without inoculants (CK) or with inoculation of two L. plantarum additives (LPI and LPII). The pH and fermentation products of silage were determined after 30 and 90 days of ensiling. Additionally, the bacterial community compositions were analyzed. The L. plantarum inoculants significantly promoted lactic acid accumulation, and Lactobacillus abundance for both periods. At 90 days, silage in CK exhibited a high pH, a loss in dry matter, and a high concentration of ammoniacal nitrogen. The inoculations of L. plantarum significantly inhibited the growth of Clostridia, and reduced ammoniacal nitrogen concentration in silage (P < 0.05). Thus, inoculation with L. plantarum improved the fermentation quality of alfalfa silage and inhibited the growth of spoilage microorganisms, and further delayed spoilage of alfalfa silage under adverse ensiling conditions.

The potential and effects of saline-alkali alfalfa microbiota under salt stress on the fermentation quality and microbial

“…The fermentation time has an important influence on silage fermentation quality and microorganisms [ 20 ]. After 30 days of ensiling, the content of CP and WSC decreased, due to LAB fermentation.…”

Assessment of Bacterial Community Composition and Dynamics in Alfalfa Silages With and Without Lactobacillus plantarum Inoculation Using Absolute Quantification 16S rRNA Sequencing

“…The microbial community plays an important role in the ensiling process. The development of PCR-based techniques enables us to define the microbial communities more accurately, and recent studies applying high through put sequencing technology have illustrated the dynamics and compositions of relative abundance of microorganism groups in alfalfa silage during ensiling process ( Guo et al, 2018 ; Ogunade et al, 2018 ; Yang et al, 2019 , 2020 ). However, the relative quantitative analyses cannot reflect the true absolute abundance of microorganism groups in a sample.…”

Effects of Lactic Acid Bacterial Inoculants on Fermentation Quality, Bacterial Community, and Mycotoxins of Alfalfa Silage under Vacuum or Nonvacuum Treatment

“…The content of NH 3 -N was determined using the phenol-hypochlorite procedure [22]. Organic acids including LA, butyric acid (BA), propionic acid (PA), and acetic acid (AA) were quantified by HPLC system (Waters Inc., Milford, MA, USA; column: Carbomix H-NP 10:8% (7.8 × 300 mm × 10 µm), Sepax Technologies, Inc., Santa Clara, CA, USA; Waters Inc.; mobile phase: 0.0254% H 2 SO 4 ; flow rate: 0.6 mL min −1 ; detector: UV detector; temperature: 55 • C; wavelength: 214 nm; injection volume: 10 µL; retention time: 22 min) [23]. The concentration of each standard solution in the standard solution was: LA, 30 mg/kg; AA, 30 mg/kg; PA, 20 mg/kg; and BA 20 mg/kg.…”

“…The WSC content in pre-ensiled alfalfa was also a key factor affecting fermentation quality, in which sufficient WSC content exceeding 60 g/kg DM was conducive to alfalfa fermentation, producing LA to reduce pH and form an acidic silage environment [3]. The WSC in alfalfa is low, and this is exacerbated after wilting [23]. In this study, the WSC content of 5.13 g/kg DM in pre-ensiled alfalfa was lower than the threshold for well-preserved silage.…”

“…In this study, silage inoculated with either LAB additive had lower NH 3 -N levels than CK. This may be due to LAB inoculation because the acidic substances produced by LAB fermentation rapidly lower pH, and the bacteriostatic and bactericidal effects of organic acids reduce fermentation by Clostridium [34], which is recognized as a typical cause of NH 3 -N accumulation [23]. This is consistent with the results of Wang et al [35], who found that inoculating one commercial inoculant of Lactobacillus plantarum and three isolated LAB strains significantly decreased the NH 3 -N levels compared with controls both in Italian ryegrass and oat silages.…”