| This study was conducted to investigate the influence of different dietary fibers on the growth performance,carcass traits,meat quality,nutrients digestibility and intestinal physiology of growing pigs.The expression of key genes and proteins associated with the intestinal immune barrier or on the pathway of glycolipid metabolism were also analyzed.Combining the microbial community and mian metabolites in the small intestine and hindgut,the possible mechanism for single or mixed ditary fibers influencing the performance and intestinal health of the animals were compared.Furthermore,the role of microflora in different intestinal segments during the regulation of different dietary fibers to the metabolism and intestinal health of host was discussed.In current study,a total of twenty-four healthy DLY growing pigs（32.42±1.95 kg）were randomly allotted to four groups according to the principle of no difference in body weight.Pigs in control group were fed with basal diet（CON）,and pigs in the other three groups were fed with basal diet plus 15%pea-hull dietary fiber（PF）,15%oat bran（OB）as well as the 7.5%pea fiber and 7.5%oat bran（MIX）,respectively.The whole study lasted for 56 days.Exp.1 The influence of different dietary fibers on the growth performance,carcass traits,meat quality,nutrients digestibility and intestinal physiology of growing pig.Results:1)Compared with CON group,the final body weight,ADFI,ADG,carcass weight and slaughter rate of pigs in PF group and the ADFI of pigs in OB group showed significantly decreased（P<0.05）.Compared with the PF group,the p H 45min and p H24h of longissimus dorsi（LM）of pigs in OB and CON group showed significantly decreased（P<0.05）.2)Compared with CON group,the digestibility of CP and NDF of pigs in PF group was significantly decreased,while the digestibility of EE and CF of these pigs showed significantly increased（P<0.05）.Meanwhile,the digestibility of DM,EE and ADF of pigs in OB group was significantly increased（P<0.05）,and the digestibility of EE,CF,and NDF of pigs in MIX group showed significantly increased（P<0.05）.3)Compared with CON group,no significant difference was found on the villus height and crypt depth of pigs fed with fiber containing diets（P>0.05）,but the jejunum crypt depth showed significantly reduced（P<0.05）.In addition,the p H value of colonic digesta of pigs in PF and MIX groups showed significantly decreased（P<0.05）compared with CON group.Results above indicates that the effect of dietary fibers on the growth performance and carcass traits of pigs is different depending on the types and sources of the fibers.Among the three dietary fibers,the poor growth performance and carcass traits of pigs fed with diet contain 15%pea fiber was probably associated with the lower digestibility of these pigs.In spite of this,the supplement of pea fiber improved the meat quality of these animals,which was mainly reflected in the improvement of the p H value of LM after slaughter.Although the supplement of 15%oat bran and mixed fiber in the diet showed an improvement on the digestibility of the pigs,no remarkerble impact on the growth performance and carcass traits was observed,which may be attributed to the shot experimental stage.We found that there was an increase in the digestibility of CF and ADF as well as a decrease of p H value in the colon of pigs fed with dietary fiber containing diets,f suggesting the role of intestinal microbes and their motablites during the degradation of these dietary fibers.Exp 2:The influence of different dietary fibers on the expression of genes associated with the lipid metabolism and glycolysis in the muscle of growing pigsResult:1)Compared with CON group,the concentration of LDL-C in the serum of pigs in OB group showed a decreased trend（P=0.051）,while the concentration of APOA1showed an increased trend（P=0.066）.Compared with MIX group,the concentration of serum APOB of pigs in OB group was significantly decreased（P<0.05）,while the concentration of APOA1showed a decreased trend（P=0.066）.2)Compared with CON group,the expression of PPAR-γgene in the LM of pigs in PF,OB,and MIX groups,and the expression of HSL gene in the LM of pigs in OB and MIX groups was significantly decreased（P<0.05）.The expression of LPL,PPAR-γ,FAS,and HSL genes in the back fat of pigs in PF group,the expression of HSL in the back fat of pigs in OB group,as well as the expression of LPL,FAS and HSL in the back fat of pigs in MIX group was also significantly decreased（P<0.05）.Compared with CON group,the expression of GPR43 gene in the liver of pigs in PF,OB and MIX groups showed significantly reduced（P<0.05）.3)Compared with CON group,the expression of My Hc IIb in the LM of pigs in PF group and the expression of My Hc IIx in the LM of pigs in MIX group was significantly decreased（P<0.05）.In addition,the expression of in the LM of pigs in PF group showed significantly lower than OB group（P<0.05）.The expression of HK-2,PKM and HTP-5B genes in the LM of pigs in PF and MIX groups,and the expression of HK-2 gene in the LM of pigs in OB group showed significantly decreased（P<0.05）compared to CON group.Results above suggests that the supplement of 15%pea-hull fiber in the diet of the growing pigs may reduce the glycolytic potential of LM in growing pigs,and in turn,to increase the p H value of muscle after slaughter.The supplement of 15%oat bran and the mixed fiber may reduce the catabolism of lipids in the LM of the growing pigs,which is beneficial to intramuscular fat deposition.The decreased expression of GPR43,a short-chain fatty acid（SCFAs）receptor gene,in the liver of pigs fed with fiber containing diets suggests that intestinal microbes and their metabolites probably mediate the reglulation of dietary fibers on the glycolipid metabolism of host.Exp 3:The influence of dietary fibers on the intestinal mucosal immune barrier of growing pigsResult:1)Compared with CON group,the expression of ZO-1 gene in the colonic mucosa of pigs in OB group was significantly decreased（P<0.05）..The expression of MUC1 and MUC2 gene in the colonic mucosa of pigs in PF,OB and MIX groups was significantly increased（P<0.05）.The expression ofβ-defensin 1 in the colonic mucosa of pigs in PF group was significantly increased（P<0.05）,while an increased trend of this gene expression was found in the colon of pigs in OF and MIX groups had（P=0.071,P=0.054）.2)In the mucosa of ilium,the expression of NOD1,TRAF6 and IL-1βgenes of pigs in PF group,and the expression of IRAK4 and TRAF6 of pigs in OB group was significantly decreased（P<0.05）,while the expression of IL-10 of pigs in OB group was increased（P<0.05）.Meanwhile,the expression of IRAK4,TRAF6 and RIPK2 genes of pigs in MIX group showed significantly decreased（P<0.05）,while the expression of IL-10 wasincreased（P<0.05）.In the mucosa of colon,compared with CON group,the expression of IL-6 gene of pigs in PF group,as well as the expression of RIPK2,TRAF6 and IL-6 genes of pigs in OB and MIX groups showed significantly increased（P<0.05）.Nevertheless,the expression of NF-κB protein showed significantly reduced in the ileum and increased in the colon of pigs fed with fiber containing diets compared to CON group（P<0.05）.Results above indicates that the supplement of 15%dietary fibers may help to enhance the defensive ability of the colonic mucus and the adaptive immunity of ilium to maintain the integrity of the intestinal barrier of growing pigs.The process of dietary fibers regluating the health of colon may be related to TLR4 and NOD involved signal pathways,while the improvement of ileum immune function may not depend on the NF-κB involved pathway.Exp 4:The influence of differnt dietary fibers on the microbial community and metabolites in the gut of growing pigsResult:1)Compared with CON group,the Shannon and Simpson index of microorganisms in the ilium of pigs in OB group was significantly decreased（P<0.05）,while PD index and Observed OTUs showed an increased trend（P=0.097,P=0.095）.The Chao1 index of microorganisms in the ilium of pigs in OB group showed an increased trend compared to PF and MIX groups（P=0.067,P=0.099）.Compared with CON group,theβdiversity index of microbes in the colon of pigs in MIX group was significantly increased（P<0.05）,while this index showed an increased trend in the colon of pigs in PF and OB groups（P=0.076,P=0.064）.2)The linear discriminant analysis and one-way ANOVA showed that the differential flora was observed among CON,OB and PF groups.All of the differential flora was identified belonging to phylum Firmicutes in the digesta of ilium of these pigs.Compared with CON group,the relative abundance of Lactobacillus was significantly increased,while the abundance of Turicibacter and unidentified genus belonging to Clostridiaceae showed significantly decreased in the ilium of pigs in PF and MIX groups（P<0.05）.Meanwhile,the abundance of unidentified genus belonging to Clostridiaceae in the ilium of pigs in OB group was also increased（P<0.05）.The differential flora in the colon among pigs in CON,OB and PF groups was identified belonging to phyla WPS,Firmicutes and Bacteroidetes.Compared with CON group,the unknown genus belonging to Clostridiaceae was significantly increased in OB group（P<0.05）,with a decrease of Lachnospira and Lactobacillus（P<0.05）.In addition,the abundance of genera Lactobacillus and Lachnospira belonging to Firmicutes in PF group and the abundance of Anaerovibrio in MIX group showed significantly increased（P<0.05）,while the abundance of Streptococcus and[Prevotella]and CF231 belonging to Bacteroidetes in PF group,as well as the abundance of Lachnospira,Streptococcus and CF231 in MIX group showed significantly decreased（P<0.05）.3)Compared with CON group,the number of Enterobacteriaceae belonging to Proteobacteria was decreased in the ilium of pigs in PF group（P=0.083）,while the number of Escherichia coli in the colon of pigs of this group showed significantly increased（P<0.05）.Meanwhile,the number ofγ-Proteobactria in the colon of pigs in MIX group showed significantly increased（）.The number of Escherichia coli in the colon of pigs in OB group was sigfnicantly lower than that in the PF group（P<0.05）4)Compared with CON group,the concentration of acetate,propionate and total SCFAs in the ileum of pigs in PF group was significantly decreased（P<0.05）,with an increase of the propionate ratio（P<0.05）.The concentration of acetae,propionate,butyrate and total SCFAs in the ilium of pigs in MIX group was significantly decreased（P<0.05）,with an increase of the acetate ratio（P<0.05）.Compared with OB group,the concentration of propionate in the colon of pigs in MIX group was significantly increased and the acetate ratio was decreased（P<0.05）.Compared with PF group,the propionate ratio in the colon of pigs in MIX group was significantly increased（P<0.05）.The ratio of acetate to propionate in the colon of pigs in MIX group was significantly lower than that in PF and OB groups（P<0.05）.Results above indicates that the supplement of 15%dietary fibers can particularly promote the growth of fiber degradation associated bacteria in the ilium and colon of growing pigs.The supplement of 15%oat bran may targetingly improve the proliferation of bacterial genera belonging to Clostridiaceae in the gut of growing pigs.The supplement of 15%pea-hull fiber can specificly promote the growth of genera Lactobacillus and Lachnospira in the colon,and the growth of Lactobacillus in the ileum,while the genus Anaerovibrio may be the targeting bacteria of mixed dietary fibers（7.5%pea fiber and 7.5%oat bran）in colon.The anlysis of SCFAs confirmed that these change of microbial community might directly impact the microbial metabolites in the digesta,and then induce the alteration of fermentation of dietary fibers in the hindgut.Meanwhile,the abundance and numbers of conditional pathogenic bacteria can be altered by the supplement of different dietary fibers,which is closely related to the enhancement of innate immune function of host.In summary,the supplement of 15%different fibers in the diets of growing pigs was confirmed to improve the intestinal health of these pigs.And this supplement can targetingly alter the microbial community,which showed an intestinal segment-specificity.Certain sources of dietary fibers can specificly impact the number of probiotics or pathogenic bacteria in the digesta to participate in the regulation of the innate immune function of host.The adaptability of intestinal microflora to fibrous substrates can in turn promote fiber degradation and achieve a so called"additional energy effects".There are complex interactions between the phenotypes such as growth performance,carcass traits and meat quality,intestinal physiology and immune barrier function of pig,and the regulation of dietary fibers on these phenotypes depends on their structures.During this process,the composition of the microorganisms in the small intestine and hindgut presents different changes,indicating an important mediating of gut microbes. |
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