| In order to find optimal alternatives to the high dose of copper in weaned piglet diet,this study was conducted to determine the effects of dietary supplementation with different levels of copper(copper sulfate)on growth performance,immune function and gut health of weaned piglets,under normal feeding and PEDV challenged conditions.Furthermore,this study investigated the possibility of dietary single plant essential(Oregano oil,O)and compound(Plant essential oils,PEO)plant essential oils to alternate the dietary high copper and their underlying antiviral mechanisms in piglets.In addition,the results of guide to formulating dies supplementaed with low-copper diets for weaned piglets.Exp.1 Effects of dietary supplementation with different levels of copper and oregano oil on growth performance,immune function and gut structure of weaned piglets challenged with PEDVThis experiment was conducted to determine the effects of dietary supplementation with different levels of copper and low dose of copper combination with oregano oil on growth performance,immune function and gut structure of weaned piglets challenged with PEDV.Thirty-six healthy DLY piglets(Duroc×Landrace×Yorkshire,7.14±0.32 kg)with25±1 days of old were randomly assigned into six treatments.Treatments included CON ? group(control I;basal diet),CON ? group(control II;basal diet),LC group(adding 25mg/kg copper),MC group(adding 120 mg/kg copper),HC group(adding 200 mg/kg copper),and LO group(adding 25 mg/kg copper+500 mg/kg oregano oil).Each treatment had six replicates with one piglet per replicate.The source of copper was copper sulfate.After 21 d normal feeding experiment,piglets in challenged groups(CON ?,LC,MC,HC,LO)were orally inoculated with PEDV solution 30 mL(2*10~4 TCID50/mL),piglets in unchallenged group(CON ?)received the same volume of saline.The trial lasted 28 days.(1)Compared with the control groups(CON ? and CON ?)under normal feeding conditions,MC and HC groups significantly improved ADG and ADFI,while decreased F/G(P<0.05).LO group increased ADG and ADFI of piglets by 9.6%and 4.6%(P>0.05),respectively,and reduced F/G by 4.2%(P>0.05).(2)Compared with unchallenged CON ? group,PEDV infection significantly decreased ADG and ADFI of piglets in CON ? group(P>0.05),and reduced the contents of serum complements(C3 and C4)and type I interferon(IFN-?,IFN-?)(P<0.05).The diarrhea incidence in CON ? group was greater than that of CON ? group(P<0.05).In addition,PEDV infection severely damaged structures of jejunal villus in CON ? group compared that of unchallenged CON ? group.(3)Compared with PEDV-challenged group(CON ?),dietary MC and HC supplementation significantly increased ADG and ADFI of piglets(P<0.05),and effectively alleviated the symptom of diarrhea.Compared with PEDV-challenged CON ? group,MC group increased the content of interleukin-4(IL-4)(P<0.05)in jejuna mucosa,tended to increase the level of IFN-?(P<0.10),and improved structures of jejunal villus.HC group had higher serum interleukin-10(IL-10),C3,C4,IFN-?and IFN-?concentrations than those of CON ? group(P<0.05).Compared with PEDV-challenged CON ? group,the serum concentrations of interleukin-10(IL-10)and complements(C3 and C4)of piglets in LO group was increased(P>0.05)by 29.5%,11.6%and 21.9%,respectively.(4)Compared with PEDV-challenged control group(CON ?),MC,HC and LO groups improved the morphological structural of jejunal villus in weaned piglets infected by PEDV,and HC group(200 mg/kg copper)showed obvious advantages.The results showed that,under normal conditions,the growth-promoting effects of dietary supplementation with MC and HC groups on piglets were better than that of piglets in LO group.Under PEDV challenged conditions,the protective functions of dietary LO supplementation on piglets was similar to that of piglets in MC group.LO group might increase serum content of anti-inflammatory cytokines and complement contents,improve intestinal structure,thereby resulting in effectively alleviating the injury caused by PEDV.Exp.2 Effects of low-copper diets supplemented with compound plant essential oil on the growth performance,immune function and intestinal health of weaned piglets challenged with PEDVThis experiment was conducted to determine whether low-copper diet supplemented with compound plant essential oil(PEO)could effectively alleviate the negative effects of PEDV infection on growth performance,immune function and intestinal health of weaned piglets.Twenty-four healthy DLY piglets(Duroc×Landrace×Yorkshire,7.07±0.37 kg)with 26±1 days of old were randomly assigned into four treatments.Treatments included CON ? group(control I;basal diet),CON ? group(control II;basal diet),LEO group(adding25 mg/kg Cu+200 mg/kg PEO),and MC group(adding 120 mg/kg copper).Each treatment had six replicates with one piglet per replicate.The source of copper was copper sulfate.After 21 d normal feeding experiment,piglets in challenged groups(CON ?,LEO,and MC)were orally inoculated with PEDV solution of 30 mL(containing 2*10~4 TCID50/mL),piglets in unchallenged group(CON ?)received the same volume of saline.The trial lasted 25 days.(1)Compared with CON ? and CON ? groups under normal feeding conditions,LEO and MC groups improved ADG and ADFI,and reduced F/G of piglets(P<0.05).Dietary supplemented with LEO significantly decrease diarrhea index of piglets compared with CON ? and CON ? groups under normal conditions(P<0.05).Compared with the unchallenged CON ? group,PEDV infection reduced ADG and ADFI in CON ? group(P<0.05),and increased the diarrhea rate and diarrhea index of piglets(P<0.05).Compared with the PEDV-challenged CON ? group,dietary supplementation with LEO or MC improved ADFI(P<0.05),and tended to decrease the diarrhea index of piglets challenged with PEDV(P<0.10).(2)Compared with CON ? and CON ? groups under normal feeding conditions,LEO and MC both enhanced serum levels of anti-inflammatory cytokines(IL-4 and IL-10)(P<0.05),and MC improved the content of serum complement C3 of piglets(P<0.05).Compared with unchallenged CON ? group,PEDV infection in CON ? group reduced the concentration of serum LZM(P<0.05),and increased the serum levels of TNF-?and IFN-?(P<0.05).Compared with the PEDV-challenged CON ? group,LEO and MC significantly improved serum IL-4 and LZM concentrations(P<0.05),and reduced serum TNF-?level(P<0.05).LEO effectively decreased serum IL-6 and DAO levels compared with the PEDV-challenged CON ? group(P<0.05).Meanwhile,diets supplemented with MC increased IFN-?content compared with PEDV-challenged CON ? group(P<0.05).(3)Compared with CON ? and CON ? groups under normal feeding conditions,LEO and MC both significantly increasedactivities of T-AOC,T-SOD and CAT in serum(P<0.05),and LEO improved the level of serum GSH-PX in weaned piglets(P<0.05).Compared with unchallenged CON ? group,PEDV infection in CON ? group decreased the content of T-SOD in serum and jejunal mucosa(P<0.05),while PEDV infection in CON ? group increased(P<0.05)serum MDA concentration,and decreased serum T-AOC and CAT contents(P<0.05).Compared with PEDV-challenged CON ? group,diets supplemented with LEO and MC both enhanced the levels of T-AOC and T-SOD in serum and jejunal mucosa(P<0.05),and decreased serum MDA concentration(P<0.05).Furthermore,LEO improved activities of serum CAT in and T-SOD in jejuna mucosa compared with PEDV-challenged CON ? group(P<0.05).(4)Compared with unchallenged CON ? group,PEDV infection in CON ? group significantly reduced sIgA content in jejunal mucosa(P<0.05).Compared with the PEDV-challenged CON ? group,diets supplemented with LEO and MC both improved IL-4 level in jejunal mucosa(P<0.05).Diets supplemented with MC enhanced sIgA and IFN-?concentrations in the jejunal mucosa compared with PEDV-challenged CON ? group(P<0.05).(5)Compared with unchallenged CON ? group,PEDV infection in CON ? group tended to increase serum D-LA concentration and DAO activity(P<0.10).Compared with PEDV-challenged CON ? group,LEO significantly decreased serum DAO activity of piglets(P<0.05).Compared with unchallenged CON ? group,PEDV infection in CON ? group down-regulated the gene expression of Occludin in jejunal mucosa(P<0.05),and tended to decrease Claudin-1 mRNA expression level(P<0.10).Compared with the PEDV-challenged CON ? group,LEO and MC groups both inhibited the down-regulation of the Occludin and Claudin-1 mRNA expressions in jejunal mucosa(P<0.05).(6)Compared with unchallenged CON ? group,PEDV infection in CON ? group up-regulated the gene expressions of RIG-1,IFN-?,IFN-?and IL-10(P<0.05),and tended to increase IFN-?mRNA expression level in jejunal mucosa(P<0.10).Compared with PEDV-challenged CON ? group,LEO group up-regulated expressions of IFN-?and STAT1 mRNA(P<0.05),and MC group increased TLR3,IFN-?,STAT1,and IL-10 mRNA expressions in jejunal mucosa ofweaned piglets challenged with PEDV(P<0.05).These results showed that dietary 25 mg/kg copper and 200 mg/kg compound plant essential oil combination supplementation could significantly improve growth performance and exert antiviral function in weaned piglets under normal feeding and PEDV challenged conditions,which resulted from improving immune function and antioxidant capacity,enhancing genes expression of TLR3 and RIG-I signaling pathways in jejunal mucosa,and inhibiting replication of virus,maintaining integrity of the intestinal barrier function.In conclusion,PEDV infection significantly reduced immune function and antioxidant capacity of piglets,and damaged the integrity of intestinal structure and function,which resulted in the decrease of growth performance and increase of diarrhea rate of weaned piglet.Dietary supplementation with 120 mg/kg or 200mg/kg copper(copper sulfate)effectively alleviated the negative effects of PEDV infection to weaned piglets.Furthermore,low-copper diets(25 mg/kg copper)supplemented with compound plant essential oil inhibited PEDV replication,and maintained the intestinal health via regulating PRRs-mediated immune response.The results indicated that compound plant essential oils could be used as an effective alternative to the high-copper in diets of piglets. |
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