0670 the Effect of Lactobacillus Brevis and Fibrolytic Enzymes on Fermentation of Switchgrass Silages

The objective of this study was to determine the effect of Lactobacillus, enzymes, and Lactobacillus + enzymes mixture on fermentation characteristics, nutritive value, and microbial diversity of switchgrass silage. Switchgrass (Panicum virgatum L.) was harvested at vegetable stage and treated with distilled water (control), Lactobacillus brevis, fibrolytic enzymes, and L. brevis + fibrolytic enzymes (denoted C, LB, E, and LB+E, respectively) before ensiling. Treated switchgrass was ensiled in sealed 1.0-L plastic jars. Inoculation accelerated the decline of silage pH. Compared with other treatments, LB+E had the greatest decline (P < 0.05) in pH during the first 3 d of ensiling. After 30 d, for C, LB, E, and LB+E, pH declined to 5.3, 4.6, 4.8, and 3.7, respectively. There was no butyric acid detected in LB and LB+E. Lactic acid concentration of LB and LB+E increased by 5.53 times and 21.75 times than that of C, respectively. Acetic acid concentration of LB and LB+E decreased by 36.34 and 9.40%, respectively. NH3–N concentration of LB, LB+E, and E decreased by 67.7, 74.55, and 69.88%, respectively. Treatments with enzymes (E and LB+E) effectively (P < 0.05) decreased NDF and ADF concentration. Neutral detergent fiber concentration of E and LB+E decreased by 8.09 and 8.43%, respectively. Acid detergent fiber concentration of E and LB+E decreased by 3.03 and 10.88%, respectively. Crude protein content of C, LB, E, and LB+E was 77.6, 96.2, 88.0, and 97.0 g/kg DM, respectively, suggesting that inoculation increased CP content of switchgrass silage (P < 0.05). The 16S rRNA gene-based pyrosequencing was used to analyze the community of the 30-d silage, and results indicated that the diversity of microorganisms differed among treatments (P < 0.05). Enterobacter was the dominant genus in C, and the relative abundance of Enterobacter was 53.60%. Enterobacter was the dominant species in E, although the relative abundance of Enterobacter decreased to 40.67% and that of Lactobacillus increased to 26.13% in E. In LB and LB+E, Lactobacillus was the advantageous species (91.19 and 96.89%, respectively), and Enterobacter was effectively inhibited. In conclusion, the addition of bacterial and enzymatic additives can improve the switchgrass silage fermentation quality at different extent. Adding the mixture of L. brevis and fibrolytic enzymes worked more efficient than adding either L. brevis or fibrolytic enzymes, respectively.