Regulation Of Low-level Protein Diets Supplemented With Bacillus Subtilis And Xylo-oligosaccharides On Growth Performance And Intestinal Barrier Function Of Weaned Piglets

Low-protein diets can significantly reduce the use of protein feedstuff,and dietary supplementation with probiotics and prebiotics can alleviate weaning stress and promote growth of piglets,which is important to alleviate the shortage of protein resources and improve the feeding efficiency of weaned piglets in China.The present study investigated the effects of supplementing 500 g/t Bacillus subtilis(BS)in normal protein diets(NP,28–48days of age,CP level 19.99%;49–70 days of age,CP level 19.02%)and low protein level diets(LP,28–48 days of age,CP level 17.71%;49–70 days of age,CP level 16.72%),as well as supplementing 500 g/t BS and 250 g/t xylooligosaccharide(XOS)in LP diets on growth performance and intestinal health in Landrace × Yorkshire castrated boars weaned at 21 days of age,and explored the underlying mechanisms in terms of nutrient metabolism,antioxidant capacity,immune function,and intestinal microecology to provide a basis for their application in pig production.The results indicate that:1.Effects of dietary protein levels and BS supplementation on growth performance and blood parameters of weaned pigletsThe LP diet decreased ADG and increased F/G on days 1-42 of the experiment(P<0.05).Dietary BS supplementation increased(P<0.05)ADG on days 1-14,as well as ADFI on days29-42,while decreased F/G on days 1-14(P<0.05).The LP diet increased plasma TG content and LDH activity on day 14,and blood MPV content and plasma T-AOC activity on day 42.Dietary BS supplementation increased(P<0.05)plasma TP content and T-AOC and GSH-px activities on day 14 of the experiment;increased plasma TP content and T-AOC,GSH-px,and ALT activities while decreased BUN content on day 28(P<0.05);increased plasma TB,GLU and Ig G contents and CAT activity while decreased LDH activity(P<0.05)on day 42.2.Regulation of dietary protein level and BS supplementation on intestinal barrier function in weaned pigletsThe LP diet increased the m RNA expression of IL-1? in jejunum and IL-2 in ileum and colon,as well as the contents of cadaverine and indole in colon,while decreased the skatole content in colon(P<0.05).Dietary BS supplementation increased the m RNA expression of IL-10 and VH and VH/CD in jejunum;the m RNA expression of IL-2 and Occludin-1,acetate content,and VH and VH/CD in ileum;the m RNA expression of Occludin-1 and IL-1?,and tryptamine and tyramine contents in colon;while decreased indole content in colon(P<0.05).NMDS results showed that dietary CP level altered gut microbiota structure.Lef Se analysis showed that 28,7,and 22 unique OTUs were identified in the jejunum,ileum,and colon,respectively.In the jejunum,the relative abundances of Proteobacteria and Bacteroidetes were higher in the LP group and LPBS group than the NP group and NPBS group(P<0.05);in the ileum,the relative abundance of Proteobacteria was higher in the LP group than the NP group and NPBS group(P<0.05),and the relative abundance of Lactobacillus was higher in the NP group and NPBS group than the LP group(P<0.05);in the colon,the relative abundance of Spirochaetes was higher in the NP group than the LP group and LPBS group(P<0.05),and the relative abundance of Brevundimonas was higher in the LP group and LPBS group than the NP group(P<0.05).Association analysis showed that the relative abundance of Cyanobacteria in the ileum was positively correlated with acetate concentration in the NPBS group(P<0.05),the relative abundance of Dorea in the colon was positively correlated with phenethylamine and cadaverine concentrations in the LPBS group,while the relative abundance of Faecalibacterium was negatively correlated with acetate concentration in the LP group and LPBS group(P<0.05).3.Effect of LP diets supplemented with BS and XOS on growth performance and blood parameters of weaned pigletsThe LP diets supplemented with XOS increased ADGI and ADG while decreased F/G(P<0.05)on days 15-28 of the experiment,increased ADFI on days 29-42 and ADFI and ADG on days 1-42(P<0.05),and BS and XOS had an interaction effect on F/G on days15-28(P<0.05).The BS supplementation in LP diets increased plasma GSH-px activity and decreased BUN content on day 14 of the experiment(P<0.05);increased plasma TP,GLU,and Ig G contents,as well as ALT,CAT,and T-AOC activities,while decreased BUN,IL-1?,and IFN-? contents on day 28(P<0.05);and increased plasma ?-AMY and CAT activities,while decreased BUN and IL-2 contents on day 42(P<0.05).The XOS supplementation in LP diets increased plasma TP,Ig G,and GSH contents,as well as ALT,AST,and GSH-px activities,while decreased IL-1? content on day 14 of the experiment(P<0.05);increased plasma TP,GLU,Ig G,and IL-10 contents,as well as SOD and T-AOC activities,while decreased BUN content on day 28(P<0.05);and increased GSH content and ?-AMY,CAT,and GSH-px activities in plasma,as well as Eos,Bas,and MCHC contents in blood,while decreased plasma BUN content on day 42(P<0.05).4.Regulation of LP diets supplemented with BS and XOS on intestinal barrier function in weaned pigletsThe LP diets supplemented with BS increased the m RNA expression of Occludin-1 and VH and VH/CD in jejunum and ileum,increased the m RNA expression of IL-10 in ileum and colonic tryptamine and butyrate content,and decreased colonic skatole content(P<0.05).The XOS supplementation in LP diets increased(P<0.05)the m RNA expression of IL-10 and VH and VH/CD in jejunum and ileum,ileal butyrate content,and tryptamine and spermidine contents and m RNA expression of Occludin-1 and ZO-1 in colon;while decreased colonic indole content(P<0.05).The XOS supplementation increased jejunal microbial alpha diversity.NMDS results showed that XOS addition altered the microbiota structure in jejunal and ileal contents,while BS addition altered the microbiota structure in ileal content.Five and 14 unique OTUs were identified in the jejunum and ileum,respectively,by Lef Se analysis.Compared with the control group,in jejunum,the relative abundance of Coprococcus was increased in the BS group(P<0.05),the relative abundance of Ochrobactrum was increased and the relative abundances of Staphylococcus and Streptococcus were decreased in the XOS group(P<0.05),the relative abundance of Lactobacillus was increased and the relative abundances of Staphylococcus and Streptococcus were decreased in the BS-XOS group(P<0.05);in ileum,the relative abundances of Proteobacteria and Firmicutes were increased in the XOS group(P<0.05),and the relative abundances of Actinobacteria and Coprococcus were increased in the BS group(P<0.05);in colon,the relative abundance of Bifidobacterium was increased in the BS group and XOS group(P<0.05).Association analysis showed that the relative abundance of Actinobacteria was positively correlated with acetate concentration in the BS group and XOS group,while the relative abundance of Coprococcus was negatively correlated with acetate concentration in the BS group(P<0.05);the relative abundance of Firmicutes was positively correlated with valerate concentration in the XOS group(P<0.05);the relative abundance of Bifidobacterium was positively correlated with tryptamine concentration in the BS group and XOS group,and the relative abundance of Ralstonia was negatively correlated with skatole concentration in the BS group(P<0.05).In conclusion,the LP diets reduced the late growth performance of weaned piglets,while LP diet supplemented with BS could improve the early growth performance,and XOS could improve the middle and late growth performance.There was an interaction between BS and XOS in growth performance.The BS addition in diets with different protein levels,as well as BS and XOS in LP diets,can improve the antioxidant and immune functions of weaned piglets,while enhance the intestinal barrier function by improving intestinal structure,tight junctions,and intestinal microbiota balance.