Effects Of Quercetin Addition On Rumen Fermentation And Hoof Health In Goats Fed A High-concentrate Diet

In order to improve animal performance and economic profits,high-concentrate feeding has been widely used in modern intensive cattle and sheep breeding industry.However,recent studies have shown that long-term high-concentrate diet feeding has an adverse effect on rumen function and hoof health.Therefore,how to control the rumen fermentation,improve the anti-inflammatory ability and protect animal health in ruminants fed a high-concentrate diet has become the important directions in the field of ruminant nutrition research.It has been found that plant secondary metabolites have attracted more and more attention by researchers due to their antibacterial,anti-inflammatory and antioxidant effects.Quercetin,one of the secondary metabolites of plants,has strong antioxidant activity,but few reports are available on whether it can improve rumen function and hoof health in ruminants fed a high-concentrate diet.Therefore,this paper firstly explored the regulation effect of quercetin on rumen fermentation and microbial flora in vitro.On this basis,animal experiment was carried out to investigate its effect on rumen fermentation parameters in vivo.Last,we explored the function of abomasal supplementation of quercetin on performance,inflammatory cytokines and matrix metalloproteinase genes expression in goats fed a high-concentrate diet.The thesis is divided into three parts:1 Effects of quercetin addition on rumen fermentation with high concentrate as substrate in vitroThe objective of this part was to investigate the effects of quercetin supplementation on ruminal fermentation in vitro.The fermentation substrate consisted of 0.325 g concentrate,0.117 g leymus chinensis and 0.058 g alfalfa for a total of 0.5 g.The study was assigned into three groups.The supplementation amount of quercetin in the treatment group was 0.5,1.0,and 2.0 mM,respectively.Only the same substrate were existed in control group.No substrate and quercetin were existed in blank group.Each group had 4 replicates.The results revealed that,1 mM and 2 mM of quercetin addition significantly improved the total gas production of 24 hours(P<0.05).1 mM quercetin addition significantly improved the concentration of acetate(P<0.05)and butyrate(P<0.01).2 mM quercetin addition significantly improved the concentration of acetate(P = 0.01),propionate(P = 0.01),butyrate(P<0.01)and total VFA(P<0.05).2 mM quercetin addition significantly reduced 16S rRNA gene copies of Firmicutes and Bacteroidetes(P<0.01)in the fermentation liquid.The results indicated that quercetin could promote the degradation of high-concentrate diet.2 The effects of quercetin supplementation on rumen fermentation,rumen microbial flora and serum indices in goats fed a high-concentrate dietThe objective of this part was to investigate the effect of quercetin on microbial fermentation,plasma antioxidant,plasma biochemical parameters and the quantity of microbial flora of rumen in goats.Twelve goats were randomly divided into two groups:one fed high-concentrate diet without quercetin(control,n = 6)and the other fed high-concentrate diet with quercetin(treatment,n ＝ 6)for 6 weeks.Rumen content were sucked out via fistula at 0 h(before morning feeding)and 2,4,8 h after morning feeding at the 35th,38th and 41st day entering trial.Vein blood samples were collected on the 36th,39th and 42th day before morning feeding and 6 h after morning feeding.The results revealed that,the treatment group significantly increased the rumen pH value(P<0.05),isobutyrate(P<0.01),valerate(P<0.05),TAOC(P<0.05),GSH(P<0.01),serum urea(P<0,01),while decreased serum K+(P<0.01).Collectively,these results indicates that quercetin addition could improve the rumen pH value,enhance the antioxidant ability and may have a positive effect on health of the goats.3 Effects of abomasal supplementation of quercetin on performance,inflammatory cytokines,and matrix metalloproteinase genes expression in goats fed a high-concentrate dietThe objective of this part was to investigate the effect of abomasal supplementation of quercetin on performance,inflammatory cytokines,and matrix metalloproteinase genes expression in goats fed a high-concentrate diet.Ten abomasally fistulated,castrated male goats fed high-concentrate diet were assigned to either control(without quercetin,n = 5)or treatment(with quercetin,n = 5).Five goats were supplemented with quercetin(100 mg/kg BW)daily blended in physiological saline solution for 28 days,whereas the control goats added only the physiological saline solution.The results showed that supplementation of quercetin increased average daily feed intake,body weight and average daily gain significantly(P<0.01).Goats supplemented with quercetin had a higher concentration of free LPS in the rumen fluid(P<0.05).Quercetin supplementation decreased the IL-1β(P<0.05)expression and increased IL-10(P<0.05)expression in the liver when compared with control group.The expression levels of the IL-1β(P<0.01)in hoof was lower for goats supplemented with quercetin than control,and the TNF-α(P<0.05)mRNA expression also trend to decrease.The supplementation of quercetin decreased the expression of MMP-2(P<0.05)and MMP-9(P<0.01).In conclusion,abomasal supplementation of quercetin improved the animal performance,decreased the mRNA expressions of inflammatory cytokines in the liver and hoof tissues,and reduced the risk of laminitis in goats.