The effect of Bioflavex® and its pure flavonoid components on in vitro fermentation parameters and methane production in rumen fluid from steers given high concentrate diets

An in vitro assay was designed to analyze the effect of either Bioflavex® (BF) or each of its pure flavonoid components [Neoeriocitrine (NE), Naringine (NG), Isonaringine (IN), Hesperidine (HS), Neohesperidine (NH), Poncirine (PC)] added at 200 μg/g dry matter (DM) incubated substrate on rumen fermentation, methane production (CH4) and microbial population. A treatment without flavonoids was also included as a control (CTR). Rumen liquor harvested from four steers fed with high concentrate diets was used as inoculum in four 72 h incubation series. Two samples were taken at the onset of each incubation series (Time 0), and two bottles per treatment were also opened after 12 h and sampled for pH, NH3-N, volatile fatty acids (VFA) and microbiology analyses [total bacteria, Streptococcus bovis, Selenomonas ruminantium, Megasphaera elsdenii, total archaea (TA), hydrogenotrophic methanogenic archaea (HMA) and Methanosarcina spp. (as acetoclastic methanogen)] using quantitative PCR. The addition of BF or its flavonoid components mitigated the cumulative gas production (P<0.01), except for NE and PC, but no differences (P>0.10) were recorded in the gas production rate (mL/h). At 12 h post incubation methane production (mL/g DM) was reduced (P<0.01) by flavonoid addition, except for NE and NG, that did not differ from CTR. No changes were detected in total VFA concentration, but flavonoids increased propionate to the detriment of acetate proportion (P<0.01). The abundance of HMA population was reduced (P<0.01) by BF and its main components (NG and NH). Relative quantification of the lactate producing bacteria S. bovis was not affected by the addition of flavonoids except for a significant increase recorded with NE (P<0.01), whereas the concentration of the lactate consuming M. elsdenii was increased by BF, NG, NH and PC (P<0.01). Relative quantification of HMA was clearly inhibited (P<0.01) by the addition of flavonoids, this effect being more pronounced with BF, NH and NG. Concentration of Methanosarcina spp. was also inhibited by PC, NH, NG and BF (P<0.01). Addition of flavonoid substances enhances fermentation efficiency by improving propionate in detriment of acetate production and clearly depressed HMA communities.