Influence of Epiphytic Microorganisms on Silage Quality and Aerobic Exposure Characteristics of Grass Pastures

In this study, we investigated whether epiphytic microorganisms of fresh forage affect silage quality and aerobic exposure of silage by determining the changes in chemical composition, fermentation characteristics and microbial population of two grass forages (sugarcane tops and corn stover) under aerobic exposure treatments (fresh, end-of-storage and aerobic exposure periods). There were nine replicates for each of the two forage silages. The total silage time was 60 days, after which the cellar was opened for a 12-day period for aerobic exposure measurements. At the end of ensiling, the lactic acid content of corn stover silage (116.78 g/kg DM) was significantly higher than that of sugarcane top silage (16.07 g/kg DM; p < 0.01), and the corn stover (3.53) had a significantly lower pH than sugarcane tops (4.46) (p < 0.01). Weissella was the most abundant epiphytic lactic acid bacteria (LAB) in sugarcane tops and corn stover (19.08% and 11.15%, respectively). The relative abundance of epiphytic Pediococcus was higher in sugarcane tops (0.17%) than in corn stover (0.09%; p < 0.05). The relative abundance of Pediococcus was significantly higher in sugarcane top silage (2.24%) than in corn stover silage during the aerobic exposure period (p < 0.01). The acetic acid content of corn stover silage was significantly reduced during aerobic exposure (p < 0.01) due to the abundance of Paenibacillus (62.38%). The fungal genus Candida affected the aerobic exposure of sugarcane top (37.88%) and corn stover silage (73.52%). In summary, Weissella was the genus of lactic acid bacteria present in the highest abundance in sugarcane tops and corn stover, favoring early and rapid acidification. In addition, Candiada, which consumes organic acids in large numbers, was the fungal genus that influenced the aerobic exposure of sugarcane top silage versus corn stover silage.