Effects of the citrus flavonoid extract Bioflavex or its pure components on rumen fermentation of intensively reared beef steers

Two experiments were performed to study the effects of the citrus flavonoid extract Bioflavex (BF; Interquim SA, FerrerHealthTech, Sant Cugat, Barcelona, Spain) or its components on the rumen fermentation of a high-concentrate diet. In an in vivo experiment, eight Friesian steers (398 +/- 12.2 kg bodyweight) fitted with a rumen cannula were given a basal concentrate (CTR) or a CTR supplemented with BF (450 mg/kg dry matter, DM) in a 2 x 4 crossover design. No differences were observed in performance parameters of BF and CTR steers. Diet BF increased pH values and the molar proportion of propionate and reduced lactate concentration as a result of an increase in the relative abundance of lactate-consuming microorganism Selenomomas ruminantium (P < 0.01) and Megaesphaera elsdenii (P = 0.06). In an in vitro experiment, the effect of BF and its pure flavonoid components added to the incubation medium was studied separately. Bioflavex and its main components naringine, neohesperidine (NH) and poncirine (PC) were added to the incubation medium at 500 mu g/gDM, with the unsupplemented substrate also included as a control (CTR). After 12 h of incubation, flavonoid mixture and NH and PC reduced (P < 0.01) the volume of gas produced and the molar proportion of acetate (P < 0.01), and increased that of propionate (P < 0.01). PC reduced the relative quantification of Streptococcus bovis, whereas NH and BF increased the relative quantification of M. elsdenii in relation to CTR (P < 0.01). Bioflavex supplementation in steers in feedlot was effective in preventing a collapse in pH and it enhanced rumen fermentation efficiency through modifying the activity of lactate-consuming bacteria and a greater molar proportion of propionate and a reduction of that of acetate, suggesting its positive role in modulating the activity of rumen microbiota.