Using γ-ray irradiation and epiphytic microbiota inoculation to separate the effects of chemical and microbial factors on fermentation quality and bacterial community of ensiled Pennisetum giganteum.

AIMS: This study aimed to separate the effects of chemical and microbial factors on the fermentation quality and bacterial community of ensiled Pennisetum giganteum. METHODS AND RESULTS: Fresh P. giganteum of two vegetative stages (stage I, GI ; stage II, GII ) was treated as follows: GI epiphytic microbiota + Î³-ray presterilized GI (MI CI ), GII epiphytic microbiota + Î³-ray presterilized GI (MII CI ), GI epiphytic microbiota + Î³-ray presterilized GII (MI CII ), and GII epiphytic microbiota + Î³-ray presterilized GII (MII CII ). Triplicates per treatment were sampled after 30 days of ensiling for chemical and microbial analyses and high-throughput sequencing. Silages made from CII (MI CII and MII CII ) had higher lactic acid concentration and the ratio of lactic to acetic acid, and lower pH and ammonia nitrogen concentration than silages produced by CI (MI CI and MII CI ). Species differential analyses showed that the changes of chemical composition rather than epiphytic microbiota significantly affected the relative abundance of Lactobacillus, Pediococcus and Pantoea in P. giganteum silages. CONCLUSION: These above results manifested that chemical composition was the main factor influencing the fermentation quality and bacterial community of P. giganteum silage in this study. SIGNIFICANCE AND IMPACT OF THE STUDY: The obtained results may, therefore, be the first record to provide an in-depth understanding of the relative contributions of chemical and microbial parameters on fermentation quality and bacterial community, which is of great importance for modulating silage fermentation and improving silage quality.