Effects of Sucrose, Glucose and Molasses on Fermentation Quality and Bacterial Community of Stylo Silage

To better understand the mechanism underlying water-soluble carbohydrates (WSC)-regulated silage fermentation, the bacterial community and fermentation quality of stylo (Stylosanthes guianensis) ensiled without (sterile distilled water) (CK) or with 10 g/kg sucrose (S), 10 g/kg glucose (G), and 10 g/kg molasses (M) were investigated. Each treatment was ensiled in three plastic bag silos for 30 days. The DM of stylo was 301.0 g/kg (fresh matter basis), while the contents of CP, WSC, NDF and ADF were 104.9, 12.3, 510.4 and 407.6 g/kg (dry matter basis), respectively. The bacterial community was characterized by using 16Sr DNA sequencing technology. The addition of WSC significantly altered both fermentation quality and the bacterial community of stylo silage. The additive treatment resulted in higher lactic acid (17.2 vs. 67.0 g/kgDM), lower pH (4.68 vs. 4.46), and lower acetic acid (37.0 vs. 28.9 g/kgDM) compared with the control. In addition, no propionic acid and butyric acid were detected in the additive treatment groups. These results indicated that WSC additives helped to produce greater quality stylo silage. Meanwhile, the Shannon index was higher, and the Simpson index was lower in the WSC additive-treated groups compared with the control, indicating that WSC improved microbial diversity. Furthermore, WSC treatments increased the abundance of acid-producing bacteria Megamonas and Bacteroides, decreased the abundance of Weissella, and inhibited the growth of the undesirable Enterobacter. Our results confirmed that sucrose, glucose and molasses have similar beneficial effects on both bacterial community and silage fermentation of stylo. Molasses was recommended to be used in stylo silage for economic benefit and resource utilization