In Vitro Effects Of Soybean Oligosaccharide And Its Functional Components On Skatole Production And Cecal Microbiota Composition Of Broilers

Skatole,a compound formed by the bacterial degradation of L-tryptophan(L-try),is responsible for one of the main contributor to chicken excreta malodorous.Soybean oligosaccharide(SBO)is produced from soybean and its by-products,it is a kind of oligosaccharide,which contains a certain amount of stachyose(STA),raffinose(RAF)and sucrose(SUC).The aim of this study was to investigate the in vitro effects of SBO and its functional components on the skatole production of broilers,and to explore the microbiological mechanisms.This experiment used a single-factor completely random design,the 42 days of age broiler cecal contents was the fermentation bacteria source.In this experiment,SUC,STA,RAF,SBO and control group were set up respectively,each group had 3 replicates.The volume of in vitro fermentation broth was 200 mL,the amount of L-try was 250 μmol/L,each treatment group on the basis of control group was supplemented with the same amount of SUC,STA,RAF,SBO.Each treatment group had a blank contrast without L-try,but the other ingredients were the same,in order to correct the content of indole and skatole.This experiment was carried out at 39 ℃ under anaerobic culture.Cumulative gas production,indole,skatole and organic acids concentrations,pH,microbiota composition and populations were analyzed after 24 h fermentation.The(?)showed that:(1)Skatole and fermentation parameters:① at 39 ℃ for 24 h,the cumulative gas production in fermentation broth of SUC,STA and SBO groups were signficantly higher than those of in control and RAF group(P<0.01).The control group had the lowest cumulative gas production;② the indole concentrations in fermentation broth of SBO,SUC,and STA groups were significantly reduced by 98.15%,97.72%and 94.17%than that of the control group(P<0.01),respectively;③ the concentrations of skatole in the fermentation broth of SBO,SUC,STA and RAF groups were significantly reduced by 79.04%,71.88%,70.28%and 62.42%than that of the control group,respectively(P<0.05);④ the degradation rate of L-try in fermentation broth of SUC,STA and SBO groups were significantly lower than that of in RAF group and control group(P<0.01);⑤ in addition,SBO and its functional components had no significant effect on the concentration of acetate in the fermentation broth(P>0.05),and had a significant effect on the concentration of lactate and pH value(P<0.01).The concentration of lactate in SUC group was the highest than other groups(P<0.01),and it was higher than control group by 75.44%，while pH value(7.46)of the control group was higher than that of the other groups(P<0.01)except for the RAF group.(2)The microbiota composition:the microbiota composition was analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis(PCR-DGGE),the results showed that the bacterial diversity index in the fermentation samples of each groups was not significant(P>0.05).The microbiota evenness in fermentation broth of SBO group was lower than that of the control group(P<0.05).SUC and other three groups compared to the control group had significant difference in microbiota richness(P<0.05);the microbiota similarity in the fermentation broth of SBO group,STA group,RAF group were higher than that of in control group;in the case of specific bands,the experimental groups with SBO and its components had three specific bands,their similarity bacteria are belong to Blautia producta,Parabacteroides distasonis,Lactobacillus reuteri.These indicated that the addition of SBO and its functional components can promote the growth of the above bacteria and reduce the production of indole and skatole.(3)The microbiota populations:the populations of Escherichia coli,lactobacilli,Bifidobacteria and total bacteria were analyzed by real-time quantitative PCR technique.The results showed that:the population of total bacteria from high to low in turn,were SBO,followed by STA,SUC,RAF,and control group;the population of Escherichia coli from high to low in turn were SBO,followed by STA,SUC,RAF and control group;the population of Bifidobacteria from high to low in turn for the control,SBO,SUC,STA and RAF group;but no significant differences were observed in the population of total bacteria,Escherichia coli and Bifidobacteria among treatments(P>0.05);the population of Lactobacilli from high to low in turn for SUC,STA,SBO,RAF and control group,there was significant difference between the control and SUC,STA and SBO group(P<0.05).These results suggest that adding SBO and its functional components of experimental groups in the population of total bacteria,Escherichia coli,Lactobacilli are higher than the control group,the population of Bifidobacteria are lower than the control group.There was a negative correlation between indole concentration and total bacterial population(P<0.05),there was negative correlations between the concentration of indole and skatole,and population of Lactobacilli(P<0.05).To sum up,adding SUC,STA,and SBO in broiler cecal bacteria fermentation broth can decrease the concentrations of indole and skaole,and affect the in vitro fermentation parameters,and reduce skatole concentration by improving the microbiota richness,and increase the population of Lactobacilli.The results of skatole reduction are as follows:SBO>SUC>STA.