Dynamic changes in butyrate-producing bacterial communities during alfalfa ensiling and their potential metabolic...

Butyrate-producing bacteria are the primary microorganisms responsible for butyric acid fermentation in alfalfa silage. However, their succession dynamics remain poorly understood.

but (butyryl-CoA: acetate CoA-transferase) and buk (butyrate kinase) gene-specific primers were utilized to investigate the dynamic changes in the butyrate-producing bacteria during alfalfa ensiling, with metabolic functions predicted based on sequence data. Enterobacter was the most abundant genus during ensiling, followed by Weissella. In the but pathway, Klebsiella and Weissella were the predominant genera. With respect to the buk pathway, the relative abundance of Enterobacter increased to 36.9% within the first three days and remained consistently elevated above 33.0% throughout the subsequent period. Concurrently, the relative abundance of Clostridium stabilized within a range of 30.5%-38.2% from day 10. Redundancy analysis revealed that butyric acid and lactic acid were the key physicochemical factors influencing butyrate-producing bacteria in the but pathway, whereas acetic acid and butyric acid played a critical role in regulating these bacteria in the buk pathway. Carbohydrate metabolism and amino acid metabolism were the main metabolic pathways associated with butyrate-producing bacteria in these two functional groups.

Butyrate-producing bacterial communities in alfalfa silage exhibit significant changes. Butyric acid and acetic acid are the most critical physicochemical factors that influence the dynamics of butyrate-producing bacteria through the but and buk pathways, respectively.