Synergistic Effects of Exogenous Lactobacillus plantarum and Fibrolytic Enzymes on Fermentation Quality, Fiber Degradation, and In Vitro Digestibility of Napiergrass (Pennisetum purpureum) Silage

This experiment aimed to evaluate the effects of exogenous L. plantarum, fibrolytic enzymes, and their combination on fermentation quality, structural carbohydrate components, and in vitro dry matter digestibility (IVDMD). The treatments included (i) no additives (control), (ii) L. plantarum (L), (iii) fibrolytic enzymes (E), and (iv) a combination of fibrolytic enzymes and L. plantarum (EL). After being fermented for 1, 3, 7, and 30 days, the silos were opened for subsequent analysis. L and EL increased the lactic acid content and decreased the pH value and NH3-N content compared to silages without the addition of L. plantarum (p < 0.05). Compared to the control, enzymes alone or combined with L. plantarum improved enzymatic hydrolysis with higher water-soluble carbohydrates being retained at the early stage of ensiling; lower contents of NDF, ADF, hemicellulose, and cellulose were observed at the end of ensiling (p < 0.05). The IVDMD was improved in E and EL silage, and the highest IVDMD was observed in E. The L silage showed no significant difference in terms of the structural carbohydrate components or IVDMD compared to the control (p > 0.05). A principal component analysis showed that L. plantarum addition did not contribute to an increase in IVDMD, whereas LA fermentation was further enhanced when EL was synergistically involved.