Effect Of High Rice Bran Diet On Intestine Development And Gut Microbiota Of Suhuai Pigs

With the sustained and rapid development of animal husbandry,the contradiction between food and feed are becoming increasingly acute,which lead from the "DLY"rearing patterns based on corn-soybean diet.Seeking lean-type pig breeds with high fibre tolerance and using indigenous feed resources with extensive source and lower cost have become the important solutions.Suhuai pig is a new Chinese cultivated lean-type pig breed,characterized by high lean rate from its father and high forage tolerance from its mother.However,the underlying mechanisms of forage tolerance in Suhuai pig remain unclear,we speculated that it might be related to the intestinal development and large intestine flora.Rice bran was used as a resourceful energy feed in Chinese traditional native pig breeding for a long time,although it is rich in fibre,and has poor palatability.Studies have shown that rice bran exert beneficial prebiotic effects,and addition of rice bran can influence the intestinal immunity of pigs.However,the systematical studies of effectiveness of rice bran digestion and its effects on intestinal development,gut microbiota and intestinal immunity in Suhuai pigs are lacking.A total of 48 fattening Suhuai pigs,with similar BW(52.60 ±0.79 kg)and age(160 d)were allocated to 2 groups.Pigs in control group fed corn-soybean basal diet,and those in treatment group were fed high fibre rice bran diet for 75 days.The primary consideration of this study was to estimate the difference of fibre digestion between two diets,and the adaptive changes in intestinal development and structure(Experiment 1).Secondly,we investigated the effects of high content of rice bran diet on cellulolytic bacteria and its metabolites in large intestine of Suhuai pigs,and attempted to explore the potential fibre tolerance mechanism based on gut microbiota(Experiment 2).Finally,the intestinal immunological effects of rice bran diet in Suhuai pigs were analyzed(Experiment 3).Experiment 1 Effects of rice bran source high fibre diet on intestinal digestion and development of Suhuai pigsFecal samples were collected on d 0,14,28 and 75 for crude fibre digestibility analysis.At the end of the trial,all pigs were slaughtered.The weight and length of stomach,small intestine and large intestine were measured,and the tissue samples from duodenum,jejunum,ileum and colon were collected for morphological observation.Crude fiber(CF)digestibility(P<0.05)and neutral detergent fiber(NDF)digestibility(P<0.01)were significantly increased when pigs fed with rice bran diet on d 14,and no significant difference was observed on d 28.These results suggested that rice bran diet promoted CF and NDF digestibilities in the short term,and the fibre digestibilities recovered after two-week adaptation.Rice bran diets had no effects on weight and length of gastrointestinal tract(GIT)except for lower small intestine relative weight(P<0.05),lower small intestine weight ratio(P<0.05)and higher large intestine weight ratio(P<0.05).And the duodenal(P<0.01)and jejunal(P<0.05)villus height were increased in rice bran group,which indicated that rice bran fibre had beneficial effect on small intestinal morphology.Experiment 2 The adaptive characteristics of cellulolytic bacteria and its metabolites in large intestine of Suhuai pigsFecal samples were collected on d 0,14,28 and 75 for carboxymethyl cellulase(CMCase)analysis and cellulolytic bacteria detection.After slaughter,digesta samples of cecum,colon and rectum were collected for VFA measurement.Rice bran diets increased the number of Ruminococcus flavefaciens(P<0.05)on d 14,but no differences were observed on d 28 and 75.Clostridium Leptum population of rice bran diet increased on d 75(P<0.05),and the number of Ruminococcus albus had no significant change during the whole trial.These results showed rice bran fibre had stimulating effects on cellulolytic bacteria of Suhuai pigs.On d 14,rice bran fibre diet increased CMCase(P<0.01),which demonstrated increased cellulolytic bacteria activities in pigs fed rice bran diet.Compared with control diet,rice bran diet increased cecal acetate/propionate ratio(P<0.05),colonic acetate/propionate ratio(P<0.01),acetate/butyrate ratio(P<0.05)and molar proportions of propionate(P<0.05).And lower(P<0.01)molar proportions of isovalerate,isobutyrate and branched chain fatty acids were observed in rice bran diet.These results showed partially replacing of corn by rice bran had different impacts on VFA in different gut segments.Experiment 3 Effects of rice bran source high fibre diet on intestinal immunity of Suhuai pigsFecal samples were collected on d 0,14,28 and 75 for Bifidobacterium,lactobaillus spp.and Escherichia coli detection.The pH values were measured in GIT,and mucosa samples from duodenum,jejunum,ileum,cecum and colon were collected for IL-1?,IL-6 and TNF-a detection.The tissue samples from small intestine were collected for goblet cell observation.The amount of Lactobacillus spp.and Bifidobacterium were increased in pigs fed rice bran diet on d 28(P<0.05),and at the end of the trial,there was no significant difference between control diet and rice bran diet.Those results suggested that the changes in gut microbiota(Lactobacillus spp.and Bifidobacterium)were temporary rather than permanent.On d 75,no differences were observed in GIT pH,and addition of rice bran increased the number of goblet cell in duodenum(P<0.01),but not others.There was no difference in proinflammatory cytokines(IL-1?,IL-6 and TNF-?)in duodenum,jejunum,ileum,cecum or colon between control diet and rice bran diet.Those results showed that rice bran applied in the diet caused some immunostimulatory effects in the gut of Suhuai pigs.In conclusion,feeding Suhuai pig with partial rice bran diet improved intestine development,and efficiently utilized rice bran source high fibre diet by regulating the abundance of cellulolytic bacteria and activity of CMCase.Although rice bran source high fibre diet had no significant effect on intestinal immunity of Suhuai pig,increased the amount of Lactobacillus spp.and Bifidobacterium.All dates implied that it is feasible to feed Suhuai pig with 35%rice bran source high fibre diet.