Effects of Formic Acid and Lactic Acid Bacteria on the Fermentation Products, Bacterial Community Diversity and Predictive Functional Characteristics of Perennial Ryegrass Silage in Karst Regions

Abstract

The effects of additives on perennial ryegrass (Lolium perenne L., LP) silage’s metabolites, microbial diversity and microbial metabolic pathways have been less studied in karst areas. This experiment sought to ascertain the impact of formic acid (F) and lactic acid bacteria (LAB) preparations introduced in karst locations on the fermentation products of LP silage, the makeup of bacterial population and the projected functional characteristics. The experiment proceeded as follows: (1) for the CK treatment, 5 mL kg−1 fresh weight (FW) of distilled water was added; (2) for the F treatment (88%), 5 mL kg−1 FW of formic acid was added; (3) for the L treatment, Lactobacillus plantarum was mixed with Lactobacillus brucei at 2 × 107 cfu/g FW. For 7, 15 and 45 days, the silage samples were kept at room temperature (20–25 °C). On day 45, the amount of lactic acid (LA) in the silage samples was substantially higher (p < 0.05) in the F (6.56% DM) and L (6.94% DM) treatments than in the CK treatment (4.47% DM), and the F treatment also had significantly lower pH and NH3-N contents than the CK and L treatments. The concentration of lactic acid (LA) was significantly higher (p < 0.05) in the F (6.56% DM) and L (6.94% DM) treatments than in the CK treatment (4.47% DM). On day 45, the dominant genera for the F and L treatments were Lactiplantibacillus (28.78% and 20.34%), Lentilactobacillus (18.85% and 12.67%) and Secundilacillus (5.01% and 13.25%), while Hafnia-Obesumbacterium (16.94%) had a higher abundance in the CK treatment. The F and L treatments promoted microbial metabolic pathways such as “metabolism”, “genetic information processing” and “organismal systems”. They reduced other microbial metabolic pathways such as “membrane transport”, “signal transduction” and “ABC transport”. In summary, F and L can enhance the quality of LP silage in karst areas by improving the structure and function of microbial communities.