Effects of Different Moisture Levels and Additives on the Ensiling Characteristics and In Vitro Digestibility of Stylosanthes Silage

Simple Summary The silage fermentation of Stylosanthes is one of the most effective solutions to solve the shortage of feed due to the inability of Stylosanthes to grow in winter. In our previous study, it was found that the effect of direct silage fermentation was poor due to factors such as the high buffer energy value and high fiber content. In this study, we used the transgenic engineered lactic acid bacteria independently developed by our team as additives to explore the effects of cellulase-producing engineered lactic acid bacteria on the fermentation quality and in vitro digestibility of Stylosanthes silage under different raw material moisture contents. The results are discussed in terms of chemical composition. We found that lactic acid bacteria can produce a large amount of cellulase in the process of Stylosanthes silage fermentation, significantly reduce the fiber content in Stylosanthes, and improve the quality and in vitro digestibility of Stylosanthes silage. Our research results provide a deeper understanding of the influence of moisture content and lactic acid bacteria additives on Stylosanthes silage, and provide technical support and a theoretical basis for guiding production practice and further in-depth research, development and utilization of more warm-season forage silage. The present study aims to estimate the dynamic effects of moisture levels and inoculants on the fermentation quality and in vitro degradability of Stylosanthes silage. In this experiment, Stylosanthes was ensiled with (1) no additive (control), (2) Lactobacillus plantarum (LP), (3) Lactobacillus plantarum carrying heterologous genes encoding multifunctional glycoside hydrolases (xg), or (4) LP + xg and was wilted until different moisture levels (60% and 72%) were attained. The ensiled bags were unpacked after different storage periods to determine the chemical composition and fermentation quality of the Stylosanthes silage. Moreover, the in vitro degradability was also determined 45 days after the ensiling process. The results show that the silage prepared with freshly mowed Stylosanthes also had a lower pH and NH3- N content. Adding transgenic engineered lactic acid bacteria xg not only decreased the NDF and ADF content of the silage, but also improved the in vitro digestibility significantly. We concluded that the addition of xg to Stylosanthes silage can improve its quality and increase in vitro digestibility and gas production. The results provide technical support and a theoretical basis for the utilization of warm-season forage silage.