Study On The Effect Of Citrus Flavonoids On Growth Performance,Antioxidant Function And Intestinal Health Of Weaned Piglets

The aim of this study was to investigate the effects of citrus flavonoids supplementation on growth performance,immune performance,antioxidant function,small intestinal mucosa morphology,intestinal related protein and gene expression as well as colonic microflora changes in weaned piglets,and evaluate whether citrus flavonoids can replace antibiotics as well.Fifty 28-day-old healthy weaned piglets(Duroc×Landrace×Yorkshire)were randomly divided into 5 groups(10 replicates per group with one pig per replicate): the control group was fed with basic diet(CON);75 mg / kg of chlortetracycline was added into the basic diet as the antibiotic group(CTC group);the three test groups respectively added the 20,40,or 80 mg / kg of citrus flavonoids into the basic diet(CF20,CF40 or CF80).The piglets were restrictively housed and fed individually.The trial lasted for 28 days.The experimental results showed that:(1)Compared with the CON group,the CF40 and CF80 groups significantly improved the final weight,ADG and ADFI of weaned piglets(P< 0.05),and the CF40 and CF80 groups significantly reduced the feed-to-weight ratio and diarrhea index(P< 0.05).(2)There was no significant effect on the organ index of weaned piglets among all group,compared with the CON group,the CTC,CF40 and CF80 groups significantly reduced the p H value of the middle duodenum of piglets(P< 0.01).(3)Compared with the CON group,citrus flavonoids can significantly increased the activity of pepsin,jejunal lipase,ileal lipase,jejunal alpha-amylase,ileal alpha-amylase and trypsin(P< 0.05).(4)Compared with the CON group,citrus flavonoids significantly increased serum alkaline phosphatase activity(P< 0.01).Serum aspartate aminotransferase and alanine aminotransferase activities were significantly decreased in CF80 group(P< 0.01),but the diamine oxidase in serum was significantly increased(P< 0.01).CF40 and CF80 significantly reduced the contents of D-lactic acid and endotoxin in serum(P< 0.01)and increased the contents of IGF-Ⅰ(P< 0.01)and prostaglandin E2(P< 0.05).The CF40 group significantly increased the content of nitric oxide(P< 0.05).(5)Compared with the CON group,citrus flavonoids significantly increased the concentrations of serum IgA,IgM and IgG(P< 0.01),and increased the contents of IL-4,IL-10 and TGF-β in serum(P< 0.01)but the contents of IL-2,IL-6,IL-8,IFN-γ and TNF-α decreased in serum(P< 0.05).(6)Compared with the CON group,CF40 significantly increased serum and liver T-AOC and T-SOD in piglet(P< 0.05),but decreased the activity of MDA(P< 0.05).Citrus flavonoids and CTC increased CAT in piglet serum and liver(P <0.05),and CTC increased serum and liver GSH-Px(P <0.05).(7)Compared with the CON group,CF80 significantly increased the duodenal villi height / crypt depth ratio(V/C)(P< 0.01);CF40 and CF80 significantly increased the jejunum V/C(P< 0.01),and the number of lymphocytes in CF80 group was significantly larger than CTC and CON groups(P< 0.01);CF80 significantly increased the ileal villi height and the number of goblet cells(P< 0.05),and increased the ratio of V/C as well as the number of lymphocytes(P< 0.01).(8)Compared with the CON group,citrus flavonoids significantly increased the relative expression of HO-1,NQO-1 and Nrf2 proteins in the liver(P< 0.05).Citrus flavonoids and CTC increased the relative expression level of HO-1,NQO-1,Nrf2 and Occludin proteins in intestinal mucosa of piglet(P< 0.05),but CF40 and CF80 groups reduced the relative expression level of NF-κB.(9)Compared with the CON group,citrus flavonoids increased the relative expression level of intestinal tight junction proteins ZO-1 and Occludin mRNA(P< 0.05),and increased the relative expression of immune factor IL-10 mRNA(P< 0.05),the relative expression levels of NF-ΚB,TLR2 and TNF-α mRNA were reduced(P< 0.05).Citrus flavonoids also increased the relative expression levels of antioxidant protein gene Nrf2,antioxidant enzymes HO-1 and NQO-1 m RNA(P <0.05).(10)Compared with the CON group,citrus flavonoids and CTC significantly increased the number of microbial OTU in piglet colonies(P< 0.05),and the Alpha diversity index(Chao1,ACE,Shannon,Simpson)of the microbial community in each group was not significantly influenced(P> 0.05).At the phylum level,there was no significant effect on the Firmicutes,Bacteroidetes,Proteobacteria of piglet colonic microorganisms among all group(P> 0.05),compared with the CON group,citrus flavonoids significantly reduced the relative abundance of Cyanobacteria in the colon of piglets(P< 0.05).At the family level,compared with the control group,the CTC,CF40 and CF80 groups significantly reduced the abundance of S24-7 and Paraprevotellaceae(P<0.05).At the genus level,compared with the CON group,CTC,CF40 and CF80 significantly increased Prevotella(P< 0.05),decreased Anaerovibrio,Prevotella and Ruminococcus(P< 0.05),there was a significantly decreased of Megasphaera in CTC and CF80 groups(P< 0.05).In summary,the addition of citrus flavonoids in the diet improves the growth performance of weaned piglets,reduces the rate of diarrhea in weaned piglets,improves intestinal health and promotes immunity and antioxidant capacity.It also enhances the intestinal barrier function,improves the colonic microflora diversity and relative abundance of the intestine as well as improve the intestinal microflora.Citrus flavonoids are expected to be used as a substitute for antibiotics.The addition of citrus flavonoids at 80 mg/kg is the best.