Fermentation quality and bacterial community of delayed filling stylo silage in response to inoculating lactic acid bacteria strains and inoculating time

Abstract

Abstract Background Filling silos generally takes much time in practice, which may negatively affect silage fermentation and feed intake. To clarify the effects of inoculating time, lactic acid bacteria (LAB) strains and filling time on the silage fermentation and microbes of stylo (Stylosanthes guianensis) and its silage, ensiling was quickly performed (quickly filling, QF) with or without LAB (Lactobacillus plantarum SXC48, Lb. plantarum CCZZ1 and Enterococcus faecalis XC124), and was performed after stylo inoculated with or without LAB was placed for 1 day (delayed filling, DF1) and 2 days (DF2). Results Delayed filling significantly increased pH, buffering capacity, microbial counts and lactic acid, acetic acid and NH3–N contents of stylo prior to ensiling. Inoculating Lb. plantarum SXC48 and CCZZ1 improved the fermentation quality of QF silage, indicated by more lactic acid, as well as lower pH and butyric acid content. Inoculating time significantly affected the pH and lactic acid content of silages. For the DF2 silages, inoculating SXC48 at filling was better than at chopping, while inoculating CCZZ1 had good fermentation quality, regardless of inoculating time. The results of 16S rRNA sequencing indicated that delayed filling enhanced the bacterial diversity of materials and silage, and inoculating significantly changed the composition of silage microbes. Kosakonia, Pseudomonas and Pantoea jointly dominated the fresh material, while Pantoea and Lelliottia jointly dominated the DF2 material. For the QF silages, inoculating SXC48 and CCZZ1 increased the relative abundance of Lactobacillus from 16.4% in the control silage to 76.5% and 82.0%, respectively. Pantoea and Lelliottia jointly dominated the DF silages. Inoculating SXC48 and CCZZ1 also increased the relative abundance of Lactobacillus in the DF stylo silages. Conclusions Under the present research conditions, delayed filling increased the lactic acid content and reduced the acetic acid, propionic acid and NH3–N contents of stylo silage, however, increased the bacterial diversity and relative abundance of undesirable bacteria, such as Pantoea and Lelliottia. The inoculating effectiveness varied with the LAB strains and inoculating time. Inoculating strian SXC48 at filling was better than at chopping, while inoculating strian CCZZ1 at both chopping and filling obtained the similar benefit. Graphical Abstract