Novel mechanistic understanding that Lactiplantibacillus plantarum is more capable of improving the ensiling performance of wheat straw silage than xylanase by driving certain key metabolites

Microbial and enzyme additives can improve silage performance, but there is limited comparative research on the effects of microbial and enzyme additives on improving silage fermentation quality, and the underlying microbial and metabolic pathways remain unclear. This study investigated the effects without inoculants (CK treatment) or with Lactiplantibacillus plantarum (LP treatment), xylanase (XY treatment) and their combination (LPXY treatment) on the fermentation quality, as well as on the microbial communities and metabolite profiles of the wheat straw silage. The results demonstrated that the LP treatment has a better effect on improving the fermentation quality of wheat straw silage compared to other treatments, as evidenced by markedly (p < 0.05) decreased the pH (4.06), acid and neutral fiber (ANF, NDF, 23.43 and 31.69%DM), and increased the lactic acid (LA, 965.89 mg/L) and acetic acid (AA, 656.10 mg/L) concentrations. After the fermentation process, the LP treatment significantly (p < 0.05) enhanced the abundance of Lactobacillus, reduced bacterial Shannon (p < 0.05) and increased some key metabolites content. The structural equation models (SEMs) and Pearson’s correlation results proved that the LP treatment improved the wheat straw silage fermentation quality via increasing the abundance of Lactobacillus, decreasing the diversity of bacterial community and enriching the content of certain key metabolites. The present study provides mechanistic evidence that Lactiplantibacillus plantarum additive is superior to xylanase additive and their combination on improving fermentation quality of wheat straw silage, that is, by enriching certain key metabolites to increase AA and LA concentrations, providing a reference for the cross study of silage feed fermentation microbiome and metabolome.