The ban on using antibiotics as feed additives, antibiotic resistance and the inherentproblems of developing new vaccines make a compelling case for developing alternativesfor in-feed antibiotics.The alternatives of choice have to be considered under theenvironmental conditions of the animal.Flavonoids, a group of polyphenolic compoundsfound mainly in fruits and vegetables, are one of the widely researched alternatives to theantibiotic feed additives in anma1 nutrition.The results of several in vitro studies indicatethat flavonoids could exhibit a variety of potential beneficial effects.The evidence,however, In vivo is conflicting and the real contributions of such compounds to animalperformance (including health challenges) and the mechanisms through which they actare still unclear.Biological activity of flavonoids depends on the presence or absence ofthe glycoside.After ingestion, the flavonoid glycosides are hydrolyzed into the aglycones which are then absorbed, metabolized by liver and intestinal enzymes, distributed totissue and excreted in urine.Metabolism by the got microflora is an important factor fortlavonoids bioavailability and can be affected by dietary modification. Recently there hasbeen much interest in the isolation of flavonoids degrading bacteria and identification ofdietary components that may contribute to flavonoids bioavailability.With these facts inmind,research was conducted to evaluate the in vivo growth and health responses inflavonoids fed broiler chickens while the aim of in vitro study was to isolate flavonoidsdegrading bacteria from chicken and to examine the effects of dietary components onflavonoids bioavailability.　　 IN YIVO STUDY:　　 The effects of hesperidin and genistein treatments on growth, metabolism and healthstatus were studied in meat type chickens (Gallus gallus).A total of 768 day-old broilerchickens were randomly divided into 8 groups.The birds~fed either a basal diet(control) or the basal diet supplemented with either 2.5 mg hesperidinlkg (HD1), 5 mghesperidin/kg (IiD2), 10 mg hesperidin/kg (HD3), 20 mg hesperidinlkg (HD4) 2.5 mggenistein/kg (GS 1), 5 mg genistein/kg (GS2) and 10 mg of genisteinlkg (GS3) of diet.Nosignificant differences in body weights and feed conversion ratio were observed betweencontrol and treated chicks.Glucose showed detectable decrease only on day 42 betweencontrol and chicks treated with 2.5 genistein/kg feed (GS 1 group).Cholesterol loweringeffects were observed by hesperidin (all groups) on day 21 and 2.5 to 10 mg/kg ofhesperidin and genistein on day 42.The hepatic expression of type-1 IGF receptor (IGF-1R) was stimulated with high dose of hesperidin (HD4) and low and medium doses ofgenistein (GSl and GS2) on 21 days while all doses of hesperidin and high dose ofgenistein (GS3) elevated IGF-1R gene expression on day 42.Analysis of EndocrineIndices showed that plasma triiodothyronine (T3) mostly remained unaffected whilethyroxine (T4) was elevated except that high dose of genistein (GS3) and two last dosesof hesperidin (HD3 and HD4) showed non significant effects on day 21 and 42,respectively.Glucagon designated increasing trend in a dose dependent manner for bothhesperidin and genistein supplementation on day 42.Oxidative analysis revealed thathesperidin and genistein supplementation generally reduced the plasma malondialdehyde(MDA) concentrations in a dose-related fashion.Hesperidin and genistein alsosuppressed total antioxidant capacity (TAOC) and superoxide dismutase (SOD) activityon day 21 and 42 except that high dose of genistein (GS3) did not show any significanteffect on day 42.Hesperidin, taken as a whole, resulted in marked decline in heat shockprotein 70(HSP70) gene expressions.In case of genistein, hepatic expression of HSP70decreased in GS1 and GS2 groups while increased in the GS3 group on day 21.In theantiinflammatory parameters investigation, hesperidin significantly suppressed plasmaprostaglandin E2 (PGE2) and leukotriene B4 (LTB4) levels on day 42 and hepaticinductible Nitric Oxide Synthase (iNOS) and cyclooxygenase-2 (COX-2) geneexpression on day 21.iNOS mRNA level was also down-regulated on day 42 in chickenssupplemented with 10 to 20 mg/kg of hesperidin.Age and dose specific effects ofgenistein were observed for anti-inflammatory parameters.PGE2 increased in high dose(GS3) group on day 21 whereas decreased in GS 1 and GS2 groups on day 42.LTB4 alsoreduced in GS1 and GS2 groups on both experiment days.Hepatic iNOS gene expressionaugmented with all doses of genistein on day 21 and with high dose (GS3) on day 42.However, iNOS mRNA level was down-regulated with 2.5 to 5 mg genisteinlkg feed onday 42.Hepatic COX-2 gene expression increased on day 21 and decreased on day 42 inchickens on GSl diet while results were vice versa for high dose (GS3) group.Analysisof immunity indices showed significant down-regulation for hepatic interferon-gamma(IFNy) gene expression by first two doses of hesperidin (HD1 and HD2) and upregulation for interleukin-10(IL-10) by first two doses of both hesperidia and genisteinon day 21.Hesperidin (all doses) also elevated the IL-10 mRNA level on day 42 whileIFNy gene expression increased only with high doses (HD3 and HD4).In contrast tohesperidin, high dose of genistein (GS3) decreased IFN-y gene expression on day 42.Hepatic interleukin-4 (IL-4) mRNA level did not show detectable differences betweencontrols and chicks treated with both genistein and hesperidin except that it was up-regulated with high dose of hesperidin (HD4).Intestinal intraepithelial lymphocytes(iIELs) increased in hesperidin and genistein treated chickens on both day 21 and 42depending on the dose applied.Intestinal secretary IgA (sIgA) production, overall,increased with hesperidin treatment and decreased with genistein treatment on day 21 and42.Hesperidin and genistein supplementation (10 mg/kg diet) decreased the total shortchain fatty acids (SCFA) contents in the cecum while DGGE profile remained unaffected.The present study suggests dose and age specific modulation of performance and healthindices by hesperidin and genistein in broilers.This work also provides new insights intothe mechanisms underlying the effect of these two flavonoids in vivo.　　 IN VITRO STUDY:　　 Cecal mcrobiota of chicken was screened for the bacteria involved in thebiotraasfonnatioa of flavonoids.Four anaerobic Lactobacillus like strains designated asMF-Ol, MF-02 and MF-03 and MF-07 were isolated from the cecum of chicken.MF-O1,MF-02 and MF-03 were capable of converting tlavonoid diglycosides (hesperidin andrutin) into bioactive aglycones while MF-07 was active in the deglycosylation of theisoflavone genistin and further degradation of aglycone genistein.The degradation ratesof flavonoids and influence of different carbon sources, following incubation withisolated strains, were assessed.The role of consortium in the degradation of tlavonoidsdiglycosides and modulation of bioconversion after supplementation with prebiotic(fructooligosaccharide) and organic acids to the fermentation medium was also monitored.Organic acids (lactate, acetate, butyrate or propionate) supplementation suppressed theflavonoids degradation while fructo-oligosaccharide (FOS) appeared to have prebioticpotential by preserving aglycones in vitro.These Lactobacillus microorganisms may leadto a combination of benefits as probiotics as well as that from transformation of flavonoiddiglycosides to bioactive aglycones.　　 CONCLUSIONO:　　 verall, the findings of this endeavor will be relevant to further understanding in vivoeffects of flavonoids in animals, particularly chickens.The dose and age related fashionin the biological activity of hesperidin and genistein may assist in explaining the largevariation between animals in the health beneficial effects of flavonoids intake.In addition,the present work may further aid in establishing age specific recommendations for the useof flavonoids in chickens.This is timely considering the current interest in thebiodegradation of flavonoids by gut microflora and use of dietary components tomodulate flavonoids bioavailability.Furthermore, it could be concluded that use of FOSmay help in preserving the deglycosylated metabolites depending upon the subclass offlavonoids.