Inoculation of Lactobacillus parafarraginis enhances silage quality, microbial community structure, and metabolic profiles in hybrid Pennisetum

Abstract Background This study investigated the effects of inoculating Lactobacillus parafarraginis alone or in combination with citric acid on the silage quality, microbial community structure, and metabolic characteristics of hybrid Pennisetum. The experiment included three treatments: (1) addition of 10 ml distilled water (CON); (2) addition of 1 × 106 cfu/g L. parafarraginis (LP); (3) addition of 1 × 106 cfu/g L. parafarraginis and 1% citric acid (LCA). The fermentation was maintained at 25 ℃ for 60 days. Results The addition of L. parafarraginis increased the dry matter, water-soluble carbohydrates, and crude protein content of the silage and decreased the fiber contents. Moreover, lactic acid content was notably higher, and pH values were lower in the L. parafarraginis group, with higher lactic acid bacteria (LAB) compared with the CON. The microbial community analysis indicated that adding L. parafarraginis promoted the proliferation of beneficial LAB and inhibited spoilage bacteria, such as Clostridium. In the LCA, amino acid metabolism was improved, particularly with an increase in L-tyrosine concentration, along with significant enrichment of pathways related to tryptophan metabolism. Conclusions The addition of L. parafarraginis improved the fermentation quality of the silage, reduced undesirable microorganisms, and increased the content of organic acids, indicating its potential to enhance the flavor of the silage. Compared with individual treatments, the combination of L. parafarraginis and citric acid improved amino acid metabolism and enriched pathways related to tryptophan metabolism, further enhancing the quality of the silage. These findings highlight the potential of L. parafarraginis, especially in combination with citric acid, as an effective additive for producing high-quality, nutritious hybrid Pennisetum silage.