Response Of Blood And Intestinal Mucosal Barrier As Well As Oxidative Stress Related Parameters In Suhuai Finishing Pigs To Diets With Varying Levels Of Defatted Rice Bran

China is the largest producer and consumer of pork in the world,pigs are mainly fed with diets based on corn-soybean.However,in recent years,demand and supply chain of conventional feedstuffs is stretched,in this situation,corn and soybean meal need to be imported in large quantity.In order to minimize the cost of breeding,the lean-type breeding pig breed that is resistant to high-fiber diets-Suhuai pigs is gradually recognized and welcomed.However,the suitable dietary fiber level is unknown in the promotion of Suhuai pigs.Rice bran has become the most representative non-conventional feed source because of its low price and wide source.It has been reported that rice bran can be used by pigs to develop its probiotics and antioxidant properties.In this experiment,varying levels of defatted rice bran were used to replace corn to form five fiber-level diets for feeding Suhuai pigs.The present work aimed to evaluate the response of blood and intestinal mucosal chemistry,immune barrier and oxidative stress-related parameters in Suhuai finishing pigs to diets with varying levels of defatted rice bran(DFRB)and preliminarily identify the optimal replacement level of corn by DFRB from the perspective of gut health,providing theoretical reference for reasonable addition of defatted rice bran and other fibrous feed materials in the diet of Suhuai finishing pigs.A total of 35 Suhuai finishing pigs with body weight(BW)of 62.90±0.78 kg were selected and allotted to five dietary treatments(7 replicates for each treatment):a control group with basal diet and four experimental diets where corn was equivalently substituted by 7%,14%,21%,28%DFRB,respectively.The whole experiment period was divided into 10-d pre-feeding of basal diet and 28-d of formal feeding of grouped diet.During the entire experiment.All pigs were housed in a temperature-controlled room with partially slatted floors.Pigs from each treatment were individually housed in pens which were equipped with the FIRE and water saving type stainless-steel drinker to allow the pigs access to feed and water ad libitum.Slaughtering was conducted on the last day.Blood samples were collected from the jugular vein of each pig for routine blood test,serum biochemistry,serum immunoglobulin G(Immunoglobulin G,IgG),immunoglobulin A(Immunoglobulin A,IgA)and immunoglobulin M(Immunoglobulin M).Mucosa samples collected from jejunum,ileum and colon were detected by Enzyme Linked Immunosorbent Assay for Secretory Immunoglobulin A(SIgA),IgM,interleukin 1β(IL-1β),interleukin 6(IL-6),interleukin 10(IL-10),interleukin 12(IL-12)and interferon y(IFN-y).Real-time quantitative PCR was used to detect the chemical barrier-related indicators including Mucin 2(MUC2),Porcine beta defensin 1(PBD1),Proline arginine rich antimicrobial peptide Proline-arginine-rich antimicrobial peptides(PR39)and oxidative stress-related indicators including nuclear factor erythroid-2 related factor-2(Nrf2),NAD(P)H:quinone oxidoreductase 1(NQOl)and hemeoxygenase-1(HO-1).The results are as follows:1.Response of routine blood test,serum biochemistry and immunoglobulin in Suhuai finishing pigs to diets with varying levels of DFRB.With the DFRB level increased in the diets,neutrophils percentage was decreased(linear and quadratic,P<0.05),lymphocytes percentage linearly increased(P<0.01),NLR linearly decreased(P<0.05),platelet distribution width exhibited cubic(P<0.05)fluctuation.With the DFRB level increased in the diets,the level of serum albumin and amylase tended to increase linearly(P=0.087 and P=0.094,respectively).There was no difference in other serum biochemistry parameters.Serum immunoglobulins(1g)showed no response to varying levels of DFRB.2.Response of intestinal mucosal barrier and oxidative stress-related parameters in Suhuai finishing pigs to diets with varying levels of DFRB.In the jejunum,with the DFRB level increased in the diets,interleukin 10(IL-10)exhibited cubic(P<0.05)fluctuation and interleukin 12(IL-12)tended to cubic(P=0.069)fluctuate.Nrf2 showed a quadratic response(P<0.05).NQO1 tended to quadratic(P=0.059)and cubic(P=0.088)response,HO-1 tended to linear(P=0.079)and quadratic(P=0.081)response.In ileum,with the DFRB level increased in the diets,IL-10 showed a trend of cubic response(P=0.064),and MUC2 expression level was up-regulated(linear,P<0.05;quadratic.P<0.05;cubic.P<0.01).The expression level of PBD1 tended to be down-regulated(linear.P=0.090;quadratic,P=0,088).The expression of Nrf2 showed linear(P<0.05)and quadratic(P<0.01)response.The expression of NQO1 tended to quadratic(P=0.093)response.The expression of HO-1 gene showed linear(P<0.05),quadratic(P<0.01)and cubic(P<0.01)response.In colon,with the DFRB level increased in the diets,the contents of IgM and IL-12 tended to increased linearly(P=0.096 and P=0.056,respectively).The content of SIgA exhibited cubic(P<0.05)fluctuation.MUC2 was up-regulated(linear,P<0.05;quadratic,P<0.05;cubic,P<0.01).The gene expression level of PR39 tended to increased linearly(P=0.057).Nrf2 and NQO1 genes showed linear response(P<0.05)and cubic(P<0.1),quadratic response(P<0.1),respectively.HO-1 showed a linear(P<0.01)and quadratic response(P<0.05).3.Calculation of the optimal replacement level of corn by DFRB.For SIgA in colon,IL-10 in jejunum,MUC2 in colon and ileum and HO-1 in ileum,the optimum levels of rice bran were 16.67%,14.00%,12.00%,12.02%and 17.14%,respectively.In conclusion,the following conclusions can be drawn:(1)Dietary rice bran can be used to improve the immune status of Suhuai finishing pigs by reducing the percentage of neutrophils,increasing the percentage of lymphocytes and lowering the level of NLR.(2)Serum immunoglobulins(Ig)showed no response to varying levels of DFRB.(3)SIgA of colonic mucosa and IL-10 contained in jejunal mucosa can play a positive role in the intestinal immune barrier in Suhuai pigs by using dietary fiber,the optimal replacement of corn by DFRB were 16.67%and 14%respectively.(4)Suhuai finishing pigs can use dietary fiber to promote MUC2 of ileum and colon in Suhuai finishing pigs,which can actively guide the intestinal chemical barrier.The optimal replacement of corn by DFRB were 12.00%and 12.02%,respectively.(5)Suhuai finishing pigs can use dietary fiber to reduce the relative expression of Nrf2 and HO-1 in ileum and Nrf2,NQO1 and HO-1 in colon.The optimal replacement of corn by DFRB was 17.14%according to the HO-1 contained in ileum.