Synergistic bacterial‒fungal interactions modulate the fermentation quality and in vitro degradation rate of triticale silage.

Abstract

Background: The humid climate and frequent rainfall during the harvest season substantially hinder the utilization of triticale as feed. Although ensiling technology can effectively preserve nutrients, its fermentation quality depends on complex microbial interactions, the core mechanisms of which remain unclear. This study proposes and validates the hypothesis that "bacterial-fungal synergy" can enhance silage fermentation. By inoculating triticale silage with Aspergillus niger (AN), Lactiplantibacillus plantarum (LP) or their combination (ANLP) and performing multi-omics analyses, the mechanism underlying this synergistic effect was systematically elucidated in this study.

Results: Compared with the control treatment, triticale silage inoculated with ANLP presented significant decreases in the neutral detergent fiber (NDF), acid detergent fiber (ADF), and ammonia nitrogen (NH₃-N) contents and significant increases in the water-soluble carbohydrate (WSC), crude protein (CP), and lactic acid (LA) contents (P < 0.05). More crucially, ANLP treatment specifically enriched Delftia, indicating a special functional role for this bacterium in triticale silage. Further metabolomic and correlation analyses revealed that the synergy between A. niger and L. plantarum not only promoted the proliferation of Delftia but also activated the phenylalanine, tyrosine, and tryptophan biosynthesis pathways. This activation drove the synthesis of phenolic acid compounds with antimicrobial and antioxidant activities, such as coumaric acid and indole derivatives. These bioactive metabolites effectively inhibited the growth of harmful microorganisms. In vitro digestibility trials confirmed that the ANLP-treated group achieved the highest dry matter and protein degradation rates, thereby validating the pathway from the microbial mechanism to end-use feed value.

Conclusions: Overall, the synergistic effects of bacteria (L. plantarum) and fungi (A. niger) can improve the fermentation quality and nutritional content of triticale by promoting amino acid metabolism and increasing the production of bioactive substances, providing a new strategy for increasing its utilization as a feed resource for ruminants.