| By LC-MS,GC-MS,NGS and other moden techniques,the effects of different dietary fiber on a)apparent digestibility;b)intestinal morphology;c)plasma metabolites;d)microbiota community and function in three intestinal segments of growing pigs were studied.From the view of plasma small metabolites and intestinal micro flora,to some extent,we elaborated the potential mechanisms which underlined the influence on nutrients metabolism induced by dietary fiber,and made clear inter-relationship among the host,microbiota and dietary fiber.The single factor completely randomized design was used in the trial,where 18 growing pigs were randomly divided into 3 groups with one pig per replicate.Each of the three experiemental groups of pigs were fed with 95% corn-soybean meal basal diet supplemented with 5% corn starch(CON),microcrystalline cellulose(MCC),or inulin(INU).The trial period was for 60 days.The results were showed as following.1)compared with CON group,inulin had a tendency of increasing ash digestibility(P = 0.08),while no change was observed in MCC group.INU had greater gross energy(GE),dry matter(DM)and carbohydrates digestibility in comparison with the MCC group(P < 0.05).INU,compared with MCC,also has significantly promoted body weight at D40(P = 0.04),D50(P = 0.04)and D60(P = 0.05).Adding dietary fiber had a trend to decrease the feed conversion ratio(P = 0.09)compared to the CON group.Compared with MCC,the inulin supplementation also tended to lower the feed conversion ratio(P = 0.08).Diets supplemented with inulin significantly increased the ileal villus height and the ratio of villus height to crypt depth(P < 0.05).An increasing trend was also observed in the ratio of villus height to crypt depth was observed in duodenum(P = 0.06)and duodenal crypt depth of MCC group was significantly lower than that of the CON group(P < 0.05).Compared with the CON group,the number of villi goblet cells(P = 0.056)was increased in the jejunum by the addition of dietary fiber.INU group and MCC group are significantly increased the number of pig colon crypt goblet cells in the colon(P < 0.05),and significant differences were also found between the two groups(P < 0.05).Ileal maltase enzyme of inulin group and MCC group differs significantly(P=0.03).The activities of lactase(P = 0.02)and maltase(P = 0.04)in the jejunum and maltase in the ileam(P = 0.04)was significantly higher in the INU group than that in the MCC group.2)The addition of MCC significantly reduced serum total cholesterol(TC)and low density lipoprotein cholesterol(LDL-C)levels(P < 0.05).Fasting serum glucagon levels were significantly decreased in the growing pigs from the INU and MCC groups(P < 0.05),but insulin levels and leptin levels were not affected(P > 0.05).Fifty-four metabolites were identified through GC-TOF/MS platform,including 9 of sugars,14 of amino acids,12 of fatty acids and 19 of other metabolites.There were considerable differences in plasma metabolites constitutions among the CON,INU and MCC groups.Compared with the CON group,growing pigs fed with dietary fiber mainly caused the changes of carbohydrate metabolism,amino acid metabolism and fat metabolism,which included 16 of metabolites.Among them,three of metabolites were involved in the carbohydrate metabolism(citric acid,erythritol and galactose);eight of metabolites were involved in amino acid metabolism(proline,leucine,isoleucine,phenylalanine,hydroxy proline,amino malonic acid,ornithine,and 5-MIAA);five metabolites were involved in lipid metabolism(heptadecanoic acid,cholesterol and oleic acid,linoleic acid,palmitic acid).Plasma ornithine was only detected in the control group.Five metabolites implicated in amino acid metabolism and one metabolite related to carbohydrate metabolism were also found differ between the MCC and INU groups.Compared with the CON group,inulin influenced the Arginine and proline metabolism pathway,and the addition of MCC mainly affected Arginine and proline metabolism;galactose metabolism;Phenylalanine metabolism;Pyruvate metabolism.Comparison between the INU and MCC groups showed the difference occured in Arginine and proline metabolism;Galactose metabolism;Linoleic acid metabolic pathway.There were negative correlations between plasma LDL-C with ornithine and erythrose(P < 0.05),and a positive correlation with the levels of proline(P < 0.05).Triglyceride,hydroxyproline and proline levels were positively correlated with TC(P < 0.05),while isoleucine,proline and hydroxyproline levels were positively related with total cholesterol(P < 0.05).The content of monounsaturated fatty acids and polyunsaturated fatty acids were positively correlated with TC levels,and wigh HDL-C and insulin,respectively(P < 0.05).3)Inulin and MCC affected the microbial community via increasing the proportion of different microbial population as well as the function of the microbial community.In different intestinal segments of growing pigs,microbial structure was modulated by DFs differently,where different key OTUs may be related to host metabolism or immunity.The COG classification system noted that strengthened function in defense mechanism,inorganic ion transport and metabolism genes in both cecum and colon of INU group,indicated by relative abundances of COGs in those dietary fiber groups.The KEGG pathway analyses showed that more metabolic pathways affected by the dietary fiber were found in the ileum than the colon.Multiple metabolic pathways implicated in the energy metabolism and disease immunity were affected by dietary fiber intake.4)The supplementation of INU and MCC both increased the percentage of butyric acid in cecum and colon,wherereas inulin increased the percentage of propionic acid,and decreased acetic acid and propionic acid ratio within the cecum and colon.Primary bile acids concentration was increased in the cecum and colon of INU group.The change in bile acids' composition and aomounts were probably due to the distinct SCFAs profile induced by different dietary fiber.Lactobacillaceae,Lachnospiraceae,Ruminococcaceae and other families of microorganisms were found to be associated with the SCFAs and primary bile acids profile and concentration.5)In order to explore the potential relationship between the variation in intestinal microbial community and metabolism of growing pigs.By multivariate statistical methods,Five,seven and six core OTUs were identified in the ileum,cecum and colon,respectively,which existed a mathematical association between the relative abundance and some of the plasma metabolites.The concurrent changes in some key bacterial species,such as Faecalibacterium prausnitzii and Lactobacillus amylovorus with a few plasma metabolites concentrations suggested that the bacteria may exert a key role of intestinal micro flora in regulating the host metabolism.Furthermore,the differed metabolites were co-products produced by microbiota and host and the biological significance needed further investigation. |
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