Ruminal Degradation of Puerarin and Its Effects on In Vitro Ruminal Fermentation, Methane Emission, and Microbial Community Structure.

Few studies have examined the effects of puerarin (PE) on ruminant parameters and methane production. Therefore, we determined the degradation of PE in the rumen and evaluated the effect of PE on in vitro fermentation, methanogenesis, and microbial community structure. A completely randomized design was used for the in vitro fermentation, and 4 gradient dosages of PE (0 mg/kg, 50 mg/kg, 100 mg/kg, and 150 mg/kg of DM) were applied in this trial. The in vitro fermentation was carried out in three runs at 6 h and 48 h, with four replicates per treatment per time point. Each run included 40 samples: eight treatments × four replicates and eight blank samples. Based on the fermentation results, both the PE treatments and the control group (CON) at 48 h were chosen for further analysis to explore the effects of PE on the bacterial community structure. Meanwhile, we determined the degradation rate and degradation products of PE in vitro ruminal fluid using high-performance liquid chromatography (HPLC). In this trial, PE may be isomerized into daidzin by rumen microorganisms; the in vitro degradation results of PE indicated that 70% of PE was degraded within 6 h, with the degradation rate reaching nearly 85% by 12 h. The concentrations of NH