| Resistant starch refers to the portion of starch that escapes digestion in the human and animal small intestine can enter the large intestine,where it is used as a substrate for bacterial fermentation,raw potato starch is a kind of starch which contains high resistant starch.Recently,resistant starch has received much attention for both its potential health benefits and functional properties in recent years.Resistant starch plays its physiological action almost by affecting the absorption of other chemicals and secondary metabolites produced by colonic fermentation,but doesn’t have an trophic effect on animal directly.So far,research on resistant starch in diets of pigs mainly focused on the intestinal tract of pigs,such as the changes of intestinal microbial composition and metabolites concentrations in pigs.However,there is little information about the effect of resistant starch on animal body.Therefore,by using raw potato starch to substitute about half of the corn starch in the diet,the present study aimed to investigate the effects of raw potato starch on the growth performance,carcass characteristics and the microbial metabolism in the large intestine of pigs.Three parts are divided into as following:1 Effects of raw potato starch on the growth performance,organ weight and intestinal morphology of pigsThis study was conducted to investigate the effects of long-term intake of raw potato starch(RPS)on the growth performance,organ weight and intestinal morphology of pigs.Thirty-six Duroc×Landrace×Large White growing barrows(70 days of age,ABW 23 kg)were randomly allocated to corn starch(CS)and raw potato starch(RPS)groups,each group consisting of six replicates(pen)with three pigs per pen.Pigs in the CS group were offered a corn-soybean based diet,while pigs in the RPS group were put on a diet in which 230 g/kg(growing)or 280 g/kg(finishing)purified corn starch was replaced with purified RPS during a 100-day trial.When pigs reached the weight of 110 kg,one pig from each pen was randomly selected for slaughtering.Liver,kidney,spleen,heart,stomach,large intestine and small intestine was segregated and weighed respectively.Duodenum,ileum,cecum and colon were separated and fixed for morphometric analysis.Results showed that long-term intake of RPS significantly increased the feed intake of the pigs(P<0.05),but had no effect on body weight,average daily gain or feed:gain ratio.Consumption of RPS significantly increased the weight of the stomach and large intestine and their percentage of body weight(P<0.05),in addition the mucosa thickness of the cecum and colon were significantly increased(P<0.05).The results suggest raw potato starch increases the feed intake of the pigs,the weight of the large intestinal and improve the intestinal morphology of cecum and colon.2 Effects of raw potato starch on the carcass characteristics,the expression of genes in the liver and colonic mucosa of pigsThis study was conducted to investigate the effects of long-term intake of raw potato starch on the carcass characteristics,the expression of genes in the liver and colonic mucosa of pigs.Materials and methods in this experiment are based on Experiment 1.When pigs reached the weight of 110 kg,one pig from each pen was randomly selected for slaughtering.Slaughter weight and carcass weight were measured,dressing percentage was calculated.After slaughter,pH,fleshcolor,pork marbling,24 h dropping loss,moisture and fat content in longissimus muscle were measured,and backfat thickness on the shoulder,thoracic waist,waist sacrum,the 6-7th rib was measured.Liver,cecal and colonic mucosa were collected immediately for subsequent RNA isolation.Genes related to fat metabolism in liver and genes related to gastrointestinal hormonal secretion in colonic mucosa were measured by real-time PCR.Cecal and colonic contents were collected for subsequent analysis of SCFA concentrations.Results showed that long-term intake of RPS decreased back fat thickness and dressing percentage(P<0.05)and had a tendency to reduce dropping loss(P<0.1),but trended to improve the pork marbling(P<0.05).As a whole,RPS had no effect on the longissimus muscle quality of growing-finishing pigs.Butyrate concentration was significantly higher in the cecal contents of pigs fed RPS as compared with CS(P<0.05),however,no significance was found in the concentration of other short chain fatty acids.But each of short chain fatty acids was increased significantly in the colonic content of pigs fed with RPS(P<0.05).Consuming RPS significantly down-regulated the genes CPT1α and PPARa,and up-regulated the expression of the SREBP1c gene in the livers of pigs(P<0.05).The genes MCT1,FFAR2 and FFAR3 were up-regulated significantly in colonic mucosa of pigs fed raw potato starch(P<0.05),however the expression of the genes PYY and Proglucagon has no significant difference between CS group and RPS group.The results suggest raw potato starch decreases backfat thickness and dressing percentage,regulates the gene expression on the fat metabolism in liver and up-regulates the gene expression related to the transportation and absorption of short chain fatty acids in the colonic mucosa.3 Effects of raw potato starch on the microbial composition and metabolites concentrations in the cecum and colon of pigsThis study was conducted to investigate the effects of long-term intake of raw potato starch on microbiota composition and their metabolites concentrations in the hindgut of growing-finishing pigs for a long time.Materials and methods in this experiment are based on Experiment 1.When pigs reached the weight of 110 kg,one pig from each pen was randomly selected for slaughtering,cecal content and colonic contents were obtained for detailed analysis.Intestinal microbiota was analyzed by high-throughput sequence and mass data of metabolites were collected by GC-MS.Result showed that the pigs fed RPS were colonized by lower amounts of total bacteria compared with pigs fed CS(P<0.05)..At the phylum level,the abundance of Firmicutes was both increased significantly in the cecal and colonic contents of pigs fed RPS(P<0.05)but the abundance of Proteobacteria,Bacteroidetes,Spirochaetae and Tenericutes trend to reduce as compared with pigs fed CS(P<0.1).At the genus level,Coprococcus,Ruminococcus and Turicibacler increase significantly,but genus of Sarcina and Clostridium were significantly decreased in the pigs fed with RPS(P<0.05).The discriminatory metabolites from GC/MS data suggested that RPS significantly increased the concentration of glucose-6-phosphate,maltose,arachidonic acid,9,12-octadecadienoic acid,oleic acid,phosphate,myo-inositol-2-phosphate,but decreased the level of a-aminobutyric acid in cecum(P<0.05).Similarly,RPS significantly increased the concentration of glucose-6-phosphate and maltose,but decreased the level of a-aminobutyric acid and putrescine in the colon(P<0.05).A metabolic pathway and metabolites sets enrichment analysis demonstrated that RPS affected significantly starch and sucrose metabolites,amino acid turnover or protein biosynthesis,lipid metabolites,glycolysis,pentose phosphate pathway,inositol phosphate metabolism and nucleotide metabolism(P<0.05).Furthemore,the correlation between the gut microbiome and metabolites shows that Ruminococcus and Coprococcus were positively correlates with glucose-6-phosphate,maltose,arachidonic acid,9,12-octadecadienoic acid,oleic acid,phosphate,but negatively correlates with α-aminobutyric acid.On the contrary,the correlation Clostridium and Sarcina with these compounds was in the opposite direction.The results suggest raw potato starch not only alters the composition and proportion of gut microbiota community but also may modulate the metabolic pathway of microbial metabolism. |
