Boussaada, AArhab, RabahCalabrò, SGrazioli, RMusco, NFerrara, MTudisco, R2025-05-062025-05-062021-12-13978-9931-9827-4-6http://dspace.univ-oeb.dz:4000/handle/123456789/22275Quercetin is a flavonoid produced as secondary metabolite by several plants; flavonoids have recently acquired considerable interest in animal nutrition for changing microbial activity and fiber digestion, increasing volatile fatty acids production and reducing methane emission (CH4). Livestock contribute to greenhouse due to CH4 resulting from rumen fermentation of feeds. Methanogens associated with protozoa are responsible for rumen CH4 production. The aim of this study was to verify the in vitro effect of pure Quercetin, added to a dairy cow diet on microbial activity, CH4 production and protozoa count. Using In vitro fermentation a diet (forage: concentrate ratio 60:40) alone as (control) and with 150 mg of pure quercetin (Sigma-Aldrich) at 39°C, under anaerobic conditions with buffered cow rumen fluid, the main fermentation parameters (pH, total gas,CH4, truly organic matter digestibility (IVOMD), VFA) were determined after 24h of incubation and protozoa count by FLOTAC technique. The addition of quercetin significantly affected most of in vitro parameters. Quercetin reduced CH4 and protozoa number, these effect can be explained by the antimicrobial activity of quercetine. FLOTAC proved useful for protozoa detection on rumen materialfrQuercetin; Fermentation; Methane; Protozoa; FLOTEC technique.Image