Dynamics of gas and greenhouse gases production during fermentation of barley silage with lactic acid bacteria

Abstract

Abstract Greenhouse gases (GHGs) are generated during fermentation in silages, especially in barley silage. However, little is known regarding the dynamics of GHG production in silages during fermentation. In the present study, GHG accumulation and reduction were assessed in barley silage. Barley was harvested at the milk stage and ensiled without (CK) or with two commercial lactic acid bacterial (LAB) additives (L1 or L2). Gas and GHG (CO2, N2O, and CH4) production, fermentation quality, fermentation weight loss (FWL), and bacterial communities were analyzed at d 0, 1, 3, 6, 15, 35, and 90 after ensiling. Gas and GHG production rapidly increased in CK during the first 3 days and in L1 and L2 during the first day and then decreased (P < 0.05), and these values were higher in CK than in L1 and L2 from d 1 to d 35 (P < 0.05), with the peak production of gas and GHG observed at d 6 in CK and at d 3 in L1 and L2. Gas and GHG production were positively correlated with the count of Coliforms and the abundances of Enterobacter, Klebsiella, and Atlantibacter from d 0 to 6 (P < 0.05) but were negatively correlated with the abundances of Lentilactobacillus, Lactiplantibacillus, and Lacticaseibacillus from d 1 to 35 (P < 0.05). L1 and L2 had increasing pH and acetic acid (AA) and decreasing lactic acid after d 15 (P < 0.05). Lentilactobacillus in L1 and L2 dominated the bacterial communities from d 35 to 90 and correlated positively with pH and AA, and negatively with LA from d 6 to 90 (P < 0.05). FWL had a positive correlation with gas and GHG from d 1 to 35 (P < 0.05). The ensiling fermentation process can be divided into gas accumulation and reduction phases. Inoculation with LAB reduced gas and GHG production. The activities of enterobacteria were the main contributors to gas and GHG accumulation. Lentilactobacillus activity mainly caused deterioration of fermentation quality during the late fermentation phase. The GHGs generated in silage contributed to the FWL during fermentation. Graphical Abstract

Keywords

• Bacterial communities
• Barley silage
• Fermentation weight loss
• Gas accumulation phase
• Gas reduction phase
• Greenhouse gases