Biochanin A Inhibits Ruminal Nitrogen-Metabolizing Bacteria and Alleviates the Decomposition of Amino Acids and Urea In Vitro

Abstract

Biochanin A is a naturally occurring flavonoid compound that is found in plant species such as red clover (Trifolium pretense) and alfalfa (Medicago sativa). Flavonoids have been reported to regulate ruminal fermentation, and the objective of this study was to evaluate the effects of biochanin A on ruminal microbial composition and nitrogen metabolism. The experiment was performed by in vitro batch culturing of a control (without biochanin A) and a biochanin A treatment. Following a 24-h incubation, gas production and the amounts of ammonia-nitrogen (NH3-N), volatile fatty acid (VFA), and amino acids were measured. Microbial population using 16S rRNA gene sequence. We found that the addition of biochanin A significantly increased microbial gas production; but had no effect on VFA production. Biochanin A supplementation also resulted in reduced microbial urease activity with half the maximal inhibitory concentration of 320 nM and also inhibited the degradation rates of total amino acids, valine, lysine, methionine and leucine by 18%, 56%, 37%, 13%, and 12%, respectively. This inhibition of urease activity and amino acid decomposition resulted in a significant reduction in the NH3-N concentration. High-throughput sequencing of the 16S rRNA sequence to monitor microbial composition showed that biochanin A significantly reduced the abundance of the proteolytic bacteria Prevotella and ureolytic bacteria Selenomonas, but increased the abundance of the lactic acid metabolizing bacteria Veillonella and Megasphaera. In conclusion, biochanin A reduced the production of ammonia by inhibiting proteolytic bacteria and their decomposition of urea and amino acids.

Urea transport and hydrolysis in the rumen: A review

“…Natural products (mostly secondary metabolites from plants such as tannins, saponins and essential oils) are sources of potential compounds for urease inhibition ( Modolo et al., 2015 ). Most recently, Liu et al. (2020) reported that Biochanin A (a natural compound) effectively inhibited rumen urease and subsequent urea degradation, thereby reducing rumen NH 3 production.…”

“…In our previous research, we investigated efficient urea utilization mechanisms; and factors affecting urease activity such as dairy cow immunization against ureases in the rumen ( Zhao et al., 2015 ), and urease inhibitory compounds ( Liu et al., 2020 ). We have also published a review about ruminal microbial urease activation, ureolytic bacteria diversity and urea recycling, but no integrated review about urea transport and hydrolysis ( Jin et al., 2018 ).…”

Forestomach fermentation and microbial communities of alpacas (<i>Lama pacos</i><i></i>) and sheep (<i>Ovis aries</i>) fed maize stalk-based diet

“…Besides, the concentration of NH 3 -N in the rumen could be associated to the degradation of dietary protein and NH 3 -N absorption by ruminal microbes (Belanche et al, 2012;Ushida et al, 1986). In the present study, higher proportions of proteolytic bacteria Selenomonas spp., which significantly increased NH 3 -N production (Liu et al, 2020), was found in sheep rumen. In addition, fibrolytic bacteria are highly dependent on NH 3 -N availability as a source of N (Russel et al, 1992).…”

Effects of Allium mongolicum Regel ethanol extract on three flavor-related rumen branched-chain fatty acids, rumen fermentation and rumen bacteria in lambs

“…A similar result was found by Jelali and Ben Salem (2014) in a study with buffalo calves offered Moringa oleifera leaf that is rich in flavonoids. Liu et al (2020) also reported that flavonoids decrease ruminal NH 3 -N concentrations in in vitro experiments. This would indicate that the AME may reduce ruminal ammonia concentrations by increasing the utilization of amino acids or promoting the synthesis of microbial proteins.…”