Effect of epiphytic microbiota from napiergrass andSudan grass on fermentation characteristics and bacterial community in oat silage.

Abstract

To investigate the effects of epiphytic microbiota from napiergrass and Sudan grass on ensiling characteristics and microbial community of oat silage. By γ-ray irradiation sterilization and microbiota transplantation technology, the sterilized oat was inoculated as follows: (a) aseptic water (STOT), (b) epiphytic bacteria on oat (OTOT), (c) epiphytic bacteria on napiergrass (OTNP) and (d) epiphytic bacteria on Sudan grass (OTSD). STOT remained in the unfermented state based on similar chemical components with fresh oat. Compared with OTOT and OTSD, higher lactic acid content and ratio of lactic acid to acetic acid, and lower pH, acetic acid and ammonia nitrogen contents were observed in OTNP after 60days of ensiling. At the late stage, Lactobacillus was the most predominant in each group. Lactococcus was eventually replaced by Lactobacillus in OTSD, whereas Lactococcus was found throughout the whole ensiling process in OTNP. Higher abundance of Weissella was observed in OTSD at the early and late stages. The result of co-occurrence network analysis proved that Lactococcus was pivotal in determining the silage fermentation pattern during ensiling. According to the 16S rRNA gene-predicted functional profiles, the inoculation of epiphytic microbiota from oat enhanced the metabolism of amino acids, whereas the inoculation of epiphytic microbiota from napiergrass and Sudan grass accelerated the carbohydrate metabolism. The epiphytic microbiota on napiergrass promoted a homo-fermentative process, whereas the epiphytic microbiota on oat and Sudan grass facilitated a hetero-fermentative pattern in oat silage, which was closely related to the abundance and metabolism of Lactococcus, Weissella and Lactobacillus. The exogenous microorganisms that promote the carbohydrate metabolism and inhibit the metabolism of amino acids could be a good potential source to improve the silage quality of temperate grass.