Study On The Protective Effects Of Palygorskite And L-Threonine On The Intestine Of Broilers

Intestinal health is an important factor that could influence the growth performance of broilers.This study selected palygorskite and L-threonine that possessed protective function on the intestinal health as experimental materials,and firstly investigated the effects of dietary supplementation with palygorskite and L-threonine on the intestinal health of broilers,respectively,and then studied the protective effects of of palygorskite and L-threonine supplementation on the intestinal health of broilers challenged with lipopolysaccharide(LPS)and related underlying mechanisms.This study consisted of the following 5 trials:Trial 1 was aimed to investigate the effects of palygorskite supplementation on the growth performance,relative weights of digestive organs,serum biochemical indices,apparent nutrient digestibility,and the digestive enzymes activities in the pancreas and jejunal chyme of broilers.A total of 144 one-day-old Arbor Acres broiler chicks were allocated into 3 dietary treatments,and each of which consisted of 6 replicates with 8 chicks per replicate(4 males and 4 females/replicate).Birds in the 3 treatments were given a basal diet supplemented with 0%(Control group),0.5%and 1.0%of palygorskite for 42 days,respectively.The results showed that dietary palygorskite supplementation did not alter growth performance of broilers(P>0.05).The concentrations of serum biochemical indices were unaffected by dietary palygorskite level(P>0.05).Compared with control group,the relative weight of pancreas was significantly increased by palygorskite supplementation at 42 day of age(P<0.05).1.0%palygorskite supplementation significantly increased apparent digestibilities of crude protein and organic matter of broilers during 32 to 34 day of age when compared with the control group(P<0.05).Similarly,dietary supplementation with 0.5%palygorskite significantly enhanced pancreatic and jejunal lipase activity at 21 day of age as compared with control group(P<0.05).In addition,birds fed the basal diet supplemented with 1.0%palygorskite exhibited a higher trypsin activity in the jejunum of broilers at 42 day of age as compared with control group(P<0.05).Trial 2 was conducted to study the effects of palygorskite supplementation on the intestinal barrier function,cecal microflora composition,immune function and antioxidant capacity of broilers.The experimental design in this trial was the same to that in the trial 1.Compared with control group,the supplementation of 1.0%palygorskite significantly decreased diamine oxidase(DAO)activity in the serum of broilers at 21 day of age(P<0.05).Broilers fed the basal diet supplemented with 1.0%palygorskite exhibited increased villus height in both jejunum and ileum of broilers at 21 day of age(P<0.05).Dietary palygorskite supplementation increased the ratio of villus height to crypt depth in both jejunum and ileum of broilers at 21 day of age(P<0.05),and the extent to increase the ratio of villus height to crypt depth in the jejunum was more pronounced when its dosage was 1.0%(P<0.05).The 1.0%palygorskite supplementation significantly increased goblet cell density in the jejunum and ileum of broilers at 21 day of age(P<0.05).Similarly,0.5%palygorskite supplementation significantly increased ileal goblet cell density of broilers at 21 day of age(P<0.05).Palygorskite supplementation significantly reduced cecal Salmonella colonies(P<0.05).Dietary 1.0%palygorskite supplementation significantly increased the concentrations of immunoglobulin M(IgM,P<0.05)and secretory immunoglobulin A(sIgA,P<0.05)in the ileal mucosa of broilers at 21 day,and the activity of superoxide dismutase(SOD)in the jejunal and ileal mucosa of broilers at 21 day(P<0.05)as well as SOD activity in the jejunal mucosa of broilers at 42 day(P<0.05).The supplementation of 1.0%palygorskite significantly increased mRNA abundances of mucin 2(MUC2,P<0.05)and zonula occludens-1(ZO-1,P<0.05),whereas significantly reduced mRNA expressions of toll-like receptor 4(TLR4,P<0.05)and interferon-y(IFN-y,P<0.05)in the ileal mucosa of broilers at 21 day.Additionally,the supplementation of 0.5%palygorskite significantly increased trefoil factor 2(TFF2)mRNA abundance in the jejunal mucosa(P<0.05),but significantly downregulated the expression of IFN-y mRNA in the ileal mucosa of broilers at 21 day of age(P<0.05).Trial 3 was designed to investigate the effects of L-threonine supplementation on the growth performance,relative weights of digestive organs,serum biochemical indices,apparent nutrient digestibility,and the digestive enzymes activities in the pancreas and jejunal chyme of broilers.A total of 144 one-day-old male Arbor Acres broiler chicks were distributed into 3 dietary treatments,and each treatment was composed of 6 replicates with 8 chicks each.Birds in the 3 treatments were given a basal diet supplemented with 0%(Control group),0.1%and 0.3%of L-threonine for 42 days,respectively.The threonine in the basal diet met the NRC requirement of broilers.Dietary L-threonine supplementation did not affect growth performance of broilers(P>0.05).Compared with control group,the supplementation 0.1%L-threonine significantly increased the relative weight of ileum of broilers at 21 day of age(P<0.05).The supplementation of L-threonine significantly increased the concentration of glucose in the serum of broilers at 21 day of age(P<0.05).Dietary supplementation with L-threonine did not affect apparent digestibilities of dry matter,organic matter,ether extract,or crude protein(P>0.05).Dietary L-threonine supplementation increased activity of pancreatic lipase of broilers at 42 day of age(P<0.05).Trial 4 was aimed to study the effects of L-threonine supplementation on the intestinal barrier function,cecal microflora composition,immune function and antioxidant capacity of' broilers.The experimental design in this trial was the same to that in trial 3.Compared with control group,the supplementation of L-threonine significantly decreased serum D-lactic acid(D-LA)content of broilers at 21 day of age(P<0.05).The supplementation of L-threonine significantly increased villus height in the ileum,and the ratio of villus height to crypt depth in both jejunum and ileum of broilers at 21 day of age(P<0.05),and the extent to increase above measured parameters was more pronounced when the dosage of L-threonine was 0.3%(P<0.05).Moreover,the supplementation of' 0.3%L-threonine significantly increased villus height in the jejunum of broilers at 21 day of age(P<0.05).Goblet cell density in the jejunum and ileum was significantly increased by L-threonine supplementation(P<0.05).The supplementation of 0.3%L-threonine significantly reduced Escherichia coli and Salmonella colonies(P<0.OS),whereas increased lactic acid bacteria colonies(P<0.05)in the cecal contents of broilers at 21 day of age(P<0.05).The supplementation of 0.3%L-threonine significantly increased relative weight of thymus of broilers at 21 day of age(P<0.05).Similarly,the relative weight of spleen was significantly increased by the supplementation of 0.1%L-threonine at 21 day of age(P<0.05).The immunoglobulin G(IgG)content in the jejunal mucosa was significantly increased by the supplementation of L-threonine at 21 day of age(P<0.05).Broilers fed the basal diet supplemented with 0.1%L-threonine exhibited increased concentrations of IgM(P<0.05)and sIgA in the jejunal mucosa of broilers at 21 day of age(P<0.05).Likewise,0.3%L-threonine supplementation significantly increased sIgA content in the ileal mucosa of broilers at 21 day of age(P<0.05).The malondialdehyde(MDA)content in the jejunal mucosa at 21 day of age,and MDA content in the serum at 42 day of age were both significantly reduced by L-threonine supplementation(P<0.05).Additionally,a higher level of L-threonine supplementation(0.3%)also reduced MDA content in the serum at 21 day of age(P<0.05).The supplementation of 0.3%L-threonine upregulated MUC2 mRNA expression(P<0.05),whereas downregulated the mRNA abundances of IFN-y and interleukin-1?(IL-1?)in the ileal mucosa of broilers at 21 day of age(P<0.05).Trial 5 was aimed to investigate the protective effects of palygorskite and L-threonine supplementation on the intestine of LPS-challenged broilers.A total of 192 one-day-old male Arbor Acres broiler chicks were allocated into 4 treatments consisting of 6 replicates with 8 chicks each.The 4 treatments were given as follows:(1)Positive control group(PC group):normal broilers given the basal diet;(2)Negative control group(NC group):LPS-challenged broilers given the basal diet;(3)Palygorskite group:LPS-challenged broilers given the basal diet supplemented with 1.0%palygorskite;(4)L-threonine group:LPS-challenged broilers given the basal diet supplemented with 0.3%L-threonine.Broilers were intraperitoneally injected with either 1.0 mg/kg body weight LPS or sterile saline at 17,19 and 21 day of age,respectively.Compared with PC group,LPS challenge significantly reduced growth performance of broilers(P<0.05).Broilers in the L-threonine group exhibited a higher average body weight whereas a lower feed/gain ratio when compared with the NC group(P<0.05).LPS challenge significantly increased the relative weights of liver and spleen(P<0.05)as well as the content of serum globulin(P<0.05).The apparent nutrient digestibility(dry matter,organic matter and crude protein)of broilers was significantly reduced by LPS challenge(P<0.05).The apparent nutrient digestibility of broilers in the palygorskite and L-threonine group was similar to that in the PC group(P>0.05).LPS challenge significantly increased the Escherichiacoli colonies(P<0.05),whereas significantly decreased lactic acid bacteria colonies in the cecal contents of broilers(P<0.05).The increased Escherichia coli and decreased lactic acid bacteria colonies in the cecal contents of LPS-challenged broilers were reversed by the supplementation of palygorskite and L-threonine(P<0.05).LPS challenge significantly increased the counts of white blood cells,mononuclear cells,and neutrophils in the blood(P<0.05).The supplementation of L-threonine significantly reduced the numbers of white blood cells in the blood of broilers challenged with LPS(P<0.05).LPS challenge significantly increased DAO activity and D-LA content in the serum of broilers(P<0.05),and the activity of DAO in the serum of LPS-challenged broilers was reversed with the supplementation of palygorskite and L-threonine(P<0.05).The serum D-LA concentration in the palygorskite group was significantly lower than that in the NC group(P<0.05).LPS challenge significantly decreased villus height in the jejunum,and the ratio of villus height to crypt depth and goblet cell density in both jejunum and ileum(P<0.05).Dietary palygorskite supplementation significantly promoted the ratio of villus height to crypt depth in the jejunum of LPS-challenged broilers(P<0.05).The supplementation of L-threonine significantly increased jejunal villus height,the ratio of villus height to crypt depth in the jejunum and ileum,and ileal goblet cell density of LPS-challenged broilers(P<0.05).LPS challenge significantly increased the concentrations of IL-1? and tumor necrosis factor-a(TNF-a)in the serum,IL-1?,TNF-a and IFN-y in the spleen,IFN-y in the jejunal mucosa,and IL-1? in the ileal mucosa of broilers(P<0.05).The supplementation of palygorskite and L-threonine reduced the concentration of TNF-a in the serum of broilers challenged with LPS(P<0.05).The concentration of IFN-y in the jejunal mucosa of LPS-challenged broilers was significantly reduced with the supplementation of palygorskite and L-threonine(P<0.05).LPS challenge significantly increased concentration of MDA in the serum and jejunal mucosa of broilers(P<0.05),but significantly decreased the content of glutathione(GSH)in the spleen,and jejunal and ileal mucosa of broilers(P<0.05).The supplementation of palygorskite and L-threonine significantly decreased MDA content in the jejunal mucosa of LPS-challenged broilers(P<0.05),whereas significantly increased the content of GSH in the jejunal mucosa of LPS-challenged broilers(P<0.05).LPS challenge significantly increased mRRNA abundances of MUC2,claudin-3(CLDN3),TLR4 and IFN-y in the jejunal mucosa(P<0.05),and IL-1? in the ileal mucosa(P<0.05),whereas decreased mRNA expression of ZO-1 in the ileal mucosa(P<0.05).The mRNA abundances of MUC2,CLDN3 and IFN-y in the jejunal mucosa,and mRNA abundance of ZO-1 in the ileal mucosa of LPS-challenged broilers were reversed with supplementation of L-threonine and palygorskite(P<0.05).Additionally,the mRNA abundance of IL-1? in the the ileal mucosa of broilers challenged with LPS was reduced by L-threonine supplementation(P<0.05).Based on the aforementioned results,it can be therefore concluded that:(1)Dietary palygorskite supplementation did not alter growth performance of broilers,but could improve the digestive function of broilers to a certain extent.(2)Dietary L-threonine supplementation especially when its dosage was 1.0%could improve intestinal barrier function and integrity,cecal microflora composition,intestinal immunity and antioxidant status of broilers at 21 day of age.(3)The addition of L-threonine to the diet that could meet the NRC requirement for threonine of broilers did not affect growth performance of broilers,whereas L-threonine supplementation would improve the digestive function of broilers.(4)Intestinal barrier function and integrity,cecal microflora composition,and intestinal immune function and antioxidant status of broilers at 21 day of age can be improved by the supplementation of L-threonine especially when its dosage was 0.3%.(5)The supplementation of palygorskite and L-threonine could exert beneficial consequences on the intestine of LPS-challenged broilers by improving digestive function,intestinal barrier function and integrity,cecal microflora composition,intestinal immunity and antioxidant capacity.