Effects Of Different Types Of Dietary Fiber On The Growth Performance,Nutrient Digestion And Liver Metabolism In Growing Pigs

In animal production,fiber is an important part of animal diets.The function of fiber is not to directly provide animals with the substances needed for growth and development,but to affect the health of the body by changing the composition of host’s intestinal microbiota and the state of fermentation.Because the special structure of the dietary fiber can resist the action of digestive enzymes and not be hydrolyzed,dietary fiber can not directly provide energy for the body.After entering the hindgut,dietary fiber can be used as fermentation substrates for microbiota in the hindgut.Fermentation produces(such as lactic acid,short-chain fatty acids and other beneficial products for the body),which are absorbed by the intestinal wall and then affect the metabolism and health of the body.Inulin,resistant starch,and pectin are several dietary fibers that are common and readily available in nature.Previous studies have showed that they can affect the digestion and absorption of other nutrients in the diet,however,different types of fibers had different effects on the absorption of other nutrients.At the same time,different types of fibers could selectively stimulate the abundance and activity of intestinal microbiota.The different structure of the microbial community will lead to the change of the combination and proportion of the fermentation products,and the effect of different fermentation products on the status of the overall metabolism of the body is different.Few studies have compared the different types of dietary fiber and the effect of different types of dietary fiber on the metabolic status of the liver,the main organ of the body’s metabolism.The purpose of this paper was to compare the effects of different dietary fiber on the growth performance,nutrient digestion and liver metabolism of growing pigs.The full paper consists of the three parts as follow:1.Effects of different types of dietary fiber on growth performance,apparent nutrient digestibility,serum and liver biochemical parameters of growing pigsThis part of the experiment mainly aimed to investigate the effects of three different types of dietary fiber on piglet growth performance,apparent nutrient digestibility,serum and liver biochemical parameters of growing pigs.28 healthy Duroc × Landrace × Large White growing pigs aged 35 days were randomly divided into 4 groups:corn starch group(control group,CON),inulin group(INU),raw potato starch group(RPS)and pectin group(PEC),each group had seven replicates,one pig for each replicate.The diets of the control group were configured with a corn-soybean meal-based diet based on the NRC nutrition standard.The inulin,resistant starch,and pectin groups were replaced corn starch with 8%inulin,raw potato starch,and pectin.The trial period lasted for a total of 40 days.In the third week of the experiment,0.3%Cr2O3 was added to the diet as an indicator,and fecal samples were collected for three consecutive days.All growing pigs fed and drank freely during the test period.During the period,strictly followed the feeding management method of the pig farm.At the end of the experiment,the pigs were slaughtered,serum was collected for serum biochemical analysis,and tissue samples from the central part of the right lobe of the liver were collected and stored for later analysis.The results showed that the final weight,average daily gain and average daily feed intake of pigs in the pectin group were significantly lower than those of other groups(P<0.05),while the feed-weight ratio was significantly higher than that of other groups.Compared with the control group,the raw potato starch diet reduced the apparent digestibility of crude protein and crude ash,and the addition of pectin significantly reduced the apparent digestibility of crude fat(P<0.05).Compared with the control group,the addition of raw potato starch or pectin reduced the concentration of aspartate aminotransferase in pig serum,while the serum low-density lipoprotein cholesterol concentration in the pectin group was significantly lower than that of the other groups.Compared with the control group,the three dietary fibers significantly reduced the content of triglycerides in the liver,while increased the content of total bile acids.The raw potato starch group significantly reduced the content of glucose and high-density lipoprotein cholesterol in the liver(P<0.05).The results showed that pectin reduced the growth performance of growing pigs,and raw potato starch and pectin affected the digestion and absorption of other nutrients.In addition,the three dietary fibers in the experiment significantly reduced the lipid content in the liver of growing pigs.The experiment results suggest that the three dietary fibers will have an effect on liver lipid metabolism,but the mode of action is different.2.Effects of different types of dietary fiber on liver metabolome of growing pigsThe purpose of this experiment was to investigate the effects of three different types of dietary fiber on pig liver metabolomes.The design of the experiment was the same as that of the first experiment,samples from the central part of the right lobe of the liver were collected and stored for subsequent metabolomics analysis.According to the screening conditions(VIP>1 and P<0.05).The results showed that the addition of inulin significantly increased the concentration of 9-(Z)-octadecenoic acid,which was mainly involved in the synthesis of fatty acids.The raw potato starch group significantly reduced the concentrations of phenylalanine and aspartic acid,which were mainly involved in the biosynthesis of aspartic acid and the metabolic pathway of phenylalanine.The concentration of cholesterol,proline and phenylalanine and other 7 amino acids in the pectin group were significantly reduced.These differential substances mainly affected lipid metabolism and various amino acid metabolic pathways.The pathway enrichment of differential metabolites showed that the addition of inulin in the diet affected the metabolic pathways such as fatty acid synthesis;and after the addition of raw potato starch,the synthesis of phenylalanine and tropane in the liver was significant affected;The steroid degradation,oxocarboxylic acid metabolism,mustard oil biosynthesis,bile acid biosynthesis,amino acid biosynthesis and other pathways in the pectin group were significantly affected.The results suggest that inulin reduced the synthesis of fatty acids in the liver,raw potato starch changed the anabolic level of two amino acids,and pectin reduced the synthesis of liver steroids while affected the synthesis and degradation of various amino acids.3.Effects of different types of dietary fiber on liver gene expression levels of growing pigsThe purpose of this experiment was to investigate the effects of three different types of dietary fiber on pig gene expression in liver.On the basis of the first experimental design,the central part of the right lobe of the liver tissue was collected for transcriptomics analysis.Differential genes were screened based on the difference fold>1.5 or<0.6,P<0.05.The results showed that compared with the control group,46 genes in the inulin group were significantly up-regulated and 47 genes were significantly down-regulated;101 genes in the raw potato starch group were significantly up-regulated and 120 genes were significantly down-regulated;109 genes in the pectin group Significantly up-regulated,69 genes were significantly down-regulated.Adding inulin significantly up-regulated the genes related to fatty acid metabolism ACSL1,SCL27A2,ACAA1,and down-regulated the FASN gene,which mainly affected the fatty acid biosynthesis pathway and PPAR signaling pathway.Genes related to lipid metabolism,ANGPTL4,ACSL1,SCL27A2,and ACAA1,were up-regulated in the raw potato starch group,while FASN and FABP1 genes were significantly down-regulated.At the same time,HMGCS2 and GPT2 related to amino acid metabolism were significantly up-regulated and PSPH was significantly down-regulated.In addition,OGDH and PCK1 related to carbohydrate metabolism in the raw potato starch group were up-regulated,while TKFC and PGM2 were down-regulated.These genes are mainly enriched in fatty acid synthesis and metabolic pathways,amino acid biosynthesis and cysteine and methionine metabolic pathways,while changed the tricarboxylic acid cycle status.The amino acid metabolism genes HMGCS1 and HASH in the pectin group were significantly up-regulated,and SCL27A2,ACAA1 and FASN related to lipid metabolism were also significantly up-regulated,indicating that pectin affected the degradation pathway of valine and leucine and the metabolism of butyrate way.The results suggested that all three dietary fiber diets could promote fatty acid oxidation and reduce lipid deposition;raw potato starch and pectin affected genes related to amino acid metabolism and promoted the degradation of multiple amino acids in the liver;raw potato starch changed carbohydrate metabolism related gene expression changes the metabolic state of carbohydrates.To sum up,the research showed that three different types of dietary fiber all reduced liver liver lipid deposition,promoted fatty acid oxidation,and inhibited fatty acid synthesis.Raw potato starch also affected the metabolism of amino acids in the liver and changed the state of carbohydrate metabolism in the liver.Compared with inulin and raw potato starch,pectin had the greatest impact on the digestion and absorption of nutrients.It affected liver lipid metabolism while increased the decomposition of various amino acids and reduced the concentration of various amino acids.