1739
The effect of a citrus extract rich in flavonoids (bioflavex®) and its main components on rumen fermentation and microbial population under in vitro system using steers fed high concentrate diet as rumen liquor donors
To evaluate the effect of flavonoids on rumen fermentation and microbial population an in vitro assay was designed. Four sets of incubation series (batches) were separately conducted using a complete randomized block design. Four steers fed high concentrate ration (90:10 comemercial concentrate:barley straw) were used as donors. Serum glass bottles (120 ml) were filled with 80 ml of an incubation solution under a CO2 stream. A mixture of the same concentrate and barley straw (600:60 mg/bottle) was used as substrate. Bioflavex® (BF) was tested against its main flavonoid components (Hesperidine [HS]; Isonaringine [IN]; Naringine [NG]; Neoeriocitrine [NE]; Neohesperidine [NH] and Poncirine [PC]) at 200µg/g DM, and the substrate without flavonoids was considered as a control (CTR). Bottles were incubated at 39±1◦C and two bottles per treatment opened after 12 h, and sampled for pH, NH3-N, volatile fatty acids (VFAs) and microbiota analyses. The DNA was extracted using QIAamp DNA Stool Mini Kit. qPCR was used to quantify the protozoa and hydrogenotrophic methanogenic archaea (HMA) concentration, moreover specific primers were used to determine the relative abundance of Streptococcus bovis, Selenomonas ruminantium and Megasphaera elsdenii in relation to the total bacteria while HMA and the acetoclastic Methanosarcina spp. were refered to total archaea. The treatments did not alter pH and no differences were recorded in NH3 nor in total VFA concentration. However, in relation to the CTR, the addition of flavonoids (except for HS), altered the VFA profile, reducing acetate and increasing propionate proportion. Ciliate protozoa concentration was reduced by BF, NG, NH and PC (P<0.05) . Flavonoids, did not alter the relative abundance of S. bovis as lactate producing bacteria, (except for NE) although they enhanced (P<0.05) M. elsdenii propotion in relation to the CTR (except for HS, IN and NE). A clear inhibition of flavonoids on the relative abundance of HMA was observed although only PC, NH, NG and BF reduced the relative abundance of Methanosarcina spp.(P<0.05). Flavonoids exert significant changes in the fermentation end products and also altered the concentration and composition of lactate-utilizing bacteria, methanogenic population and ciliate protozoa. However, the different tested flavonoids substances did not interact homogeneously against rumen population.
Keywords: Absolute and relative microbiota quantifications, in vitro incubation and Pure flavonoids