The Response Of Microflora In The Hindgut Of Mice And Pigs To Different Two Types Of Dietary Fibers

In current study,the effect of different types of dietary fibers(DF),oat derived ?-glucan(SDF),microcrystalline cellulose(MCC)and their mixture,to the microbial community structure in the feces and colonic digesta of BALB/c mice was first investigated.The core bacteria specifically utilize SDF and IDF in the hindgut of the mice were also explored.Next the dynamic response of bacteria and methanogens as well as their potential interaction in the hindgut of growing pigs was also discussed using the cross test of the two types of DF in vivo.Experiment 1 Effects of high-level dietary SDF and IDF on the growing performance,organ indexes and microbial community in the hindgut of BALB/c miceA total of 36 healthy BALB/c male mice(17.95 ± 0.95 g)were selected and randomly divided into 4 groups based on their body weight.Mice in control group were fed with basal diet(C,no non-feed-sourced fibers),while mice in the other three groups were fed with basal diet containing 28%oat derived ?-glucan(G,the purity was 70%),20%MCC(M,the purity ? 99%),and 14%glucan and 10%MCC,respectively.The nutrient levels of diet for each group was consistent.The whole experiment lasted for 21 days.Results1.High level(20%)of DF significantly reduced the average feed intake(ADFI)of the mice(P<0.01),and the trend presented as follows:C>M>GM>G.The average weight gain(AWG)of mice in different groups showed no significant differences(P>0.05).Compared to group G and M,the epididymal fat index of mice in group GM showed significantly higher(P<0.05).2.The concentration of acetate in the colonic digesta of mice in group G and GM tended to be increased compared with those in group M and C(P<0.1),in which the concentration showed 65%higher in group G than that in group C and 52%higher than that in group GM.The concentration of propionate in the colonic digesta of mice in G and GM was significantly higher that that in group M and C(P<0.01),in which the concentration showed 75%higher in group G than that in group C and 71%higher than that in group GM.4.The result of PCR-DGGE(Denaturant Gel Gradient Electrophoresis)analysis showed that at day 4,the bacterial Shannon index of fecal samples from mice in group G was significantly lower than group C(P<0.05),while at day 7,this index of samples from group G was significantly lower than the other three groups(P<0.01).At day 10,the bacterial Shannon index of fecal samples from group M showed significantly higher than group G and GM(P<0.01).5.The relative abundance of Bacteroidetes in the colon of mice in group G was significantly higher than the other three groups(P<0.01),while the abundance of this phylum in the colon of mice in group M and GM(P = 0.03,0.02,respectively)was significantly higher than group C(12.9 ± 4.2%).The relative abundance of Firmicutes in the colon of mice in group C was highest(80.1 ± 4.8%),but it showed significantly lower in the colon of mice in group G(38.7 ± 14.8%)compared to other groups(P<0.01).6.The relative abundance of ?-and ?-proteobacteria in the colon of mice in group G was significantly higher than other groups(P<0.01),while the abundance of 8-proteobacteria was significantly lower than others(P<0.01).The relative abundance of family Enterobacteriaceae was significantly lower than other groups(P<0.01).7.The bacterial genera associated with SDF utilization in the colon of mice were represented by Bacteroides spp.,Oscillospira spp.,Prevotella spp.and Ruminococcus spp..On the other hand,the bacterial genera associated with IDF utilization in the colon of mice were represented by Oscillospira spp.?Ruminococcus spp.?Desulfovibrio spp.?Coprococcus spp.and Bacteroides spp..8.The result of qPCR analysis showed that the number of SRB(Sulfate Reducing Bacteria)was significantly lower in the colon of mice in group G,while represented highest in the colon of mice in group M and GM(P<0.01).However,the absolute copy number of archaeal mcrA gene was not observed significantly changed among the different four groups(P>0.05).Our results suggested that there were core bacterial groups specifically using SDF and IDF in the hindgut of mice.Compared to IDF,more amount of short chain fatty acids(SCFAs),especially propionate and acetate,was produced through the fermentation of SDF by the bacteria in the hindgut,which in turn to possibility reduce the loss of body weight and energy induced by the decrease of ADFI by the direct supplement of energy or gluconeogenesis pathway.Experiment 2 The response of bacteria and methanogens in the hindgut of pig to the change of types of dietary fibersA total of 16 healthy and castrated growing DLY(Duroc×Landrace×Yorkshire)(40.38 ± 1.19 kg)pigs were selected and randomly divided into 2 groups according to their body weight.The whole experiment was divided into four periods.The first period lasted for one week and each of the next 3 periods lasted for 3 weeks.The supplementary DF were oat derived ?-glucan(SDF)and MCC(IDF,same as experiment 1).A cross test design was used in current study.All of the animals were fed with basal diet at the first experimental period.During the second period,pigs in one group(T1)was fed with diet containing 7.14%oat beta-glucan,while those pigs in another group(T2)was fed with diet containing 5%MCC.During the third period,pigs in group T1 were fed with the diet containing 5%MCC and pigs in group T2 were fed with the diet containing 7.14%oat beta-glucan.All pigs were fed with basal diet(same as the first period)during the last period.A digestion trial lasted for 4 days was conducted at the end of each of the last three experimental periods.The nutrient levels of basal and all fibrous diets were similar.The rectal content of each pig was collected every two days,and the rectal content was continuously collected for 3 days when the diet was changed.Results1.When the IDF containing diet was changed into SDF containing diet,the ADFI of pigs in group T2 was significantly lower than groupTl(P<0.01).2.The apparent digestibility of crude protein(CP),crude fat(EE),crude ash(Ash),crude fiber(CF)and acid detergent fiber(ADF)was significantly affected by the types of DF.Compared with those pigs fed IDF containing diet,the apparent digestibility of CP,EE and Ash of pigs fed SDF containing diet was significantly decreased(P<0.05),while the apparent digestibility of CF and ADF showed significantly increased(P<0.01).3.The real-time response of bacteria in the hindgut of pigs showed opposite to dietary SDF and IDF.The change of bacterial diversity in the hindgut of pigs fed SDF containing diet showed a reducing tendency.Compared with samples collected at day 7(the Shannon index was 3.32 ± 0.09),the bacterial Shannon index of samples collected at day 28(Shannon index was 3.51 ± 0.18)was significantly decreased(P<0.01),while the ?diversity index of bacterial in the hindgut of these pigs showed increase.On the other hand,the change bacterial diversity in the hindgut of pigs fed IDF containing diet showed an increasing tendency.Compared with samples collected at day 7(3.25 ± 0.08),the bacterial Shannon index of samples collected at day 28(3.57± 0.10)was significantly increased(P<0.01),while the ?diversity index showed decreased.4.When the type of DF changed from IDF into SDF,the responses of bacteria and methanogens in the hindgut of pigs were more sensitive and the bacterial diversity fluctuated remarkably.The bacterial Shannon index of samples collected at day 29,31,40 and 49 was 3.62 ± 0.12,3.12 ± 0.09,3.47 ± 0.06 and 3.15 ± 0.09,respectively(P<0.01).The Shannon index of methanogens showed a remarkable increase during the early period and then decreased.The Shannon index of methanogens of samples collected at day 29,31,43 and 49 was 2.77 ± 0.15,2.80 ± 0.09,2.96 ± 0.09 and 2.55 ±0.10,respectively(P<0.01).5.The relative abundance of Firmicutes in the hindgut of pigs fed SDF containing diet was increased from 73%(d7)to 82%(d8)rapidly and then decreased to 68%(d22),while the relative abundance of Bacteroidetes showed an opposite change:rapidly decreased from 17%(d7)to 6%(d8)and then increased to 19%(d22).The relative abundance of Firmicutes in the hindgut of pigs fed IDF containing diet showed decreased from 81.99%(d7)to 63.33%(d22)and then slightly increased(71.02%,d28).6.LefSe analysis showed that the specific bacterial groups in the hindgut of pigs in T1 group at the second period belonged to Actinobacteria and Firmicutes,which also included polysaccharides-utilizing bacteria such as Mitsuokella,Ruminococcaceae and Megasphaera.More specific bacterial taxa belong to Actinobacteria,Firmicutes,Proteobacteria and Bacteroidetes were found in the hindgut of pigs in T1 group at the third period.The classified genera included Sharpea,Epulopiscium and Clostridium.The number of specific bacterial taxa of samples in the samples collected at day 51(the fourth period)was the highest compared to those samples collected at other times,and belonged to Proteobacteria,Lentisphaerae,Verrucomicrobia,Bacteroidetes and Firmicutes.The specific bacteria in the hindgut of pigs in T2 group at the second period belonged to Bacteroidetes,Firmicutes and Chlamydiae,which were identified belonging to Firmicutes and Spirochaetes at the third period.The specific bacteria in the samples collected at day 51 belonged to Proteobacteria,Lentisphaerae,Verrucomicrobia,Bacteroidetes and Firmicutes.Results above showed that there were bacteria specifically using SDF and IDF in the hindgut of pigs.When the types of DF changed,the alteration of bacterial community showed more drastically compared to methanogens.The community of methanogens in the hindgut of pigs was remarkably influenced by the order of ingestion of SDF and IDF.The change of methanogen community was observed later than bacteria,indicating a complex interaction between the two microbes during the fermentation of DF in the hindgut of the pigs.The alteration of microbial community can directly impact microbial function(such as the alteration of SCFAs),and in turn,induce the fermentation in the hindgut and indirectly influence the efficiency of DF utilization of the microbes as well as the nutrients digestibility of host.In summary,there are bacteria specifically using SDF and IDF in the hindgut of both mice and pigs.The response of microbes in the hindgut to the change of fiber types is complicated,in which methanogens and bacteria have a complex interaction.High-level of SDF can be fermented in the colon to produce more SCFAs(especially propionate)compared to IDF,promoting the growth of the animals.Results of current study provide a new thought for the better utilization of different types/sources of DF in animal production.