Inulin-type fructans of longer degree of polymerization exert more pronounced in vitro prebiotic effects

AIMS: We assessed to what extent fructans of different degrees of polymerization (DP) differ in their prebiotic effectiveness towards in vitro microbial communities from the proximal and distal colon. METHODS AND RESULTS: Two short chain fructans - oligofructose (DP 2-20) and inulin (DP 3-60) - were administered to the Simulator of the Human Intestinal Microbial Ecosystem (SHIME) at 2.5 g day(-1). The influence of fructan addition towards fermentation activity and microbial community composition from the different SHIME colon compartments were evaluated. Both fructans exerted prebiotic effects with significantly higher butyrate and propionate production and stimulation of lactic acid-producing bacteria. Compared with oligofructose, it was noted that it took more time before significant effects from inulin addition were observed. Yet, the higher short-chain fatty acid production and lower proteolytic activity showed that the prebiotic effects from inulin were more pronounced than oligofructose. Also, the bifidogenic effects from inulin vs oligofructose were higher in the distal colon compartments and this effect was prolonged in the distal colon once the addition was stopped. CONCLUSIONS: Inulin has more pronounced prebiotic effects than oligofructose towards both fermentation activity and bacterial community composition in the SHIME model. SIGNIFICANCE AND IMPACT OF THE STUDY: Its slower fermentation rate and higher prebiotic potency makes inulin a more interesting compound than oligofructose to beneficially influence the microbial community from both the proximal and distal colon regions.     

Fermentation properties of gentio-oligosaccharides

AIMS: To investigate the fermentation properties of gentio-oligosaccharides (GOS), as compared to fructo-oligosaccharides (FOS) and maltodextrin in mixed faecal culture. METHODS AND RESULTS: The substrates were incubated in 24 h batch culture fermentations of human faecal bacteria. Fluorescent in situ hybridization was used to determine changes in populations of bifidobacteria, lactobacilli, clostridia, bacteroides, streptococci and Escherichia coli. Gas and short-chain fatty acid (SCFA) production was also measured. GOS gave the largest significant increases in bifidobacteria, lactobacilli and total bacterial numbers during the incubations. However, FOS appeared to be a more selective prebiotic as it did not significantly stimulate growth of bacterial groups which were not probiotic in nature. GOS and maltodextrin produced the highest levels of SCFA. Lowest gas production was seen with GOS and highest with FOS. CONCLUSIONS: GOS possessed bifidogenic activity in vitro. Although fermentation of GOS was not as selective as FOS, gas production was lower. Gas production is often seen as an undesirable side effect of prebiotic consumption. SIGNIFICANCE AND IMPACT OF THE STUDY: The study has provided the first data on fermentation of GOS in mixed faecal culture. The study has also used molecular microbiology methods (FISH) to quantify bacterial groups. The data extend our knowledge of the selectivity of fermentation of oligosaccharides by the gut microflora.     

Faecal parameters as biomarkers of the equine hindgut microbial ecosystem under dietary change

Faeces could be used for evaluating the balance of the equine hindgut microbial ecosystem, which would offer a practical method for assessing gut health and how this relates to disease. However, previous studies concluded that faeces microbial ecosystem was not representative of the proximal hindgut (caecum and ventral colon). This study aimed to evaluate if variations of the faecal microbial ecosystem were similar to those observed in the proximal hindgut. Six horses, fistulated in the caecum and right ventral (RV) colon, were subjected to a gradual change of diet, from a 100% hay (high fibre) diet (2.2 DM kg/day per 100 kg BW) to a 57% hay+43% barley (high starch) diet (0.8 DM kg/day per 100 kg BW hay and 0.6 DM kg/day per 100 kg BW barley). The two diets were iso-energetic and fed over a 3-week trial period. Samples of digesta from the caecum, RV colon and faeces were collected two times on the 10th and 20th day of the trial, for each diet to assess the microbial ecosystem parameters by both classical culture technics and biochemical methods. The variations observed in the caecal and colonic bacterial composition (increase in total anaerobic, amylolytic and lactate-utilizing and decrease in cellulolytic bacteria concentrations) and microbial activity (changes in volatile fatty acids concentrations and increase in lactate concentrations) demonstrated that the hay+barley diet caused changes in the hindgut microbial ecosystem. Similar variations were observed in the faecal microbial ecosystem. Feeding the hay+barley diet resulted in higher concentrations of faecal lipopolysaccharides. The functional bacterial group concentrations (cellulolytics, amylolytics and lactate utilizers) were significantly correlated between caecum and faeces and between colon and faeces. From analyses of the metabolites produced from microbial activity, only valerate concentration in the caecum and the proportion of propionate were significantly correlated with the same parameters in the faeces. Results of the principal component analysis performed between all the caecal/faecal and colonic/faecal parameters revealed that the total anaerobic and cellulolytic bacteria concentrations, as well as valerate, l-lactate and lipopolysaccharide concentrations were strongly correlated with several microbial parameters in the caecum (P<0.027; r>|0.45|) and in the colon (P<0.013; r>|0.50|). This demonstrated that faecal samples and their bacterial analyses could be used to represent caecum and RV colon hindgut microbial ecosystem in terms of variations during a change from a high-fibre to a high-starch diet, and thus could be markers of particular interest to diagnostic proximal hindgut microbial disturbances.     

Profiling of composition and metabolic activities of the colonic microflora of growing pigs fed diets supplemented with prebiotic oligosaccharides

It is evident that quantitative information on different microbial groups and their contribution in terms of activity in the gastrointestinal (GI) tract of humans and animals is required in order to formulate functional diets targeting improved gut function and host health. In this work, quantitative information on levels and spatial distributions of Bacteroides spp, Eubacterium spp, Clostridium spp, Escherichia coli, Bifidobacterium spp and Lactobacillus/Enterococcus spp. along the porcine large intestine was investigated using 16S rRNA targeted probes and fluorescent in situ hybridisation (FISH). Caecum, ascending colon (AC) and rectum luminal digesta from three groups of individually housed growing pigs fed either a corn-soybean basal diet (CON diet) or a prebiotic diet containing 10 g/kg oligofructose (FOS diet) or trans-galactooligosaccharides (TOS diet) at the expense of cornstarch were analysed. DAPI staining was used to enumerate total number of cells in the samples. Populations of total cells, Bacteroides, Eubacterium, Clostridium and Bifidobacterium declined significantly (P < 0.05) from caecum to rectum, and were not affected by dietary treatments. Populations of Lactobacillus/Enterococcus and E. coli did not differ throughout the large intestine. The relative percent (%) contribution of each bacterial group to the total cell count did not differ between caecum and rectum, with the exception of Eubacterium that was higher in the AC digesta. FISH analysis showed that the sum of all bacterial groups made up a small percentage of the total cells, which was 12.4%, 21.8% and 10.3% in caecum, AC and rectum, respectively. This supports the view that in swine, the diversity of GI microflora might be higher compared to other species. In terms of microflora metabolic activity, the substantially higher numerical trends seen in FOS and TOS treatments regarding total volatile fatty acid, acetate concentrations and glycolytic activities, it could be postulated that FOS and TOS promoted saccharolytic activities in the porcine colon.     

In vitro fermentability and physicochemical properties of fibre substrates and their effect on bacteriological and morphological characteristics of the gastrointestinal tract of newly weaned piglets

Abstract

Fermentability of fibre has a great impact on the bacterial flora along the gastrointestinal tract of newly weaned piglets. Therefore, this parameter was determined by incubating in vitro different fibre substrates (chicory roots, sugar beet pulp, wheat bran and corn cobs) with contents of jejunum or caecum sampled from slaughtered pigs. Incubating with small intestinal contents, lactic acid was the only fermentation product. Fermentability was highest for chicory roots, followed by wheat bran and sugar beet pulp, while corn cobs were not fermented. Based on SCFA formed in the incubations with caecal contents, ranking of the fermentability of the fibre substrates was in the same order. The effect of adding different fibre substrates to diets of newly weaned piglets on bacteriological and morphological aspects of the gastrointestinal tract was also investigated. In Experiment 1 three groups of five piglets, weaned at four weeks of age, received a control feed (C), C supplemented with corn cobs (50 g/kg) or with chicory roots (20 g/kg). In Experiment 2, diet C was supplemented with sugar beet pulp (120 g/kg) or with wheat bran (75 g/kg). After three weeks animals were euthanized and digesta were sampled from stomach, proximal and distal jejunum, caecum and colon. Furthermore, mucosal scrapings were prepared and tissue samples were taken from jejunum, caecum and colon. Viscosity was determined for jejunal, caecal and colon contents. Corn cobs in the feed increased the number of total bacteria, lactobacilli and bifidobacteria in the stomach and proximal duodenum, while a decreased count of streptococci in distal jejunum contents was noted. Chicory roots increased the counts of Escherichia coli in the distal jejunum and on the mucosa, while sugar beet pulp decreased the number of lactobacilli on the mucosa only. Wheat bran seemed to increase the count of E. coli in jejunal digesta and on the mucosa, and also the number of lactobacilli in the stomach and jejunum. Bifidobacterial numbers were increased but only in the proximal part of the jejunum. Fibre substrates affected the concentration of lactate and SCFA in different parts of the intestinal tract. Feeding corn cobs increased villus length in the proximal jejunum by 13%. The number of intra-epithelial lymphocytes in the villous epithelium of proximal and distal jejunum was decreased by corn cobs and chicory roots supplementation while beet pulp and wheat bran had the opposite effect. In Experiment 1, apoptotic index of the mucosa of the distal jejunum was very low and decreased when corn cobs were fed. Mitotic index in the crypts was only affected by the wheat bran diet and a small decrease was noted. It was concluded that the fermentability of fibre was not an ideal criterion for predicting its effects on the flora. The effect of fibres on viscosity of digesta was negligible probably explaining the lack of clear and consistent influences on the intestinal mucosa.     

In vitro fermentability and physicochemical properties of fibre substrates and their effect on bacteriological and morphological characteristics of the gastrointestinal tract of newly weaned piglets

Fermentability of fibre has a great impact on the bacterial flora along the gastrointestinal tract of newly weaned piglets. Therefore, this parameter was determined by incubating in vitro different fibre substrates (chicory roots, sugar beet pulp, wheat bran and corn cobs) with contents of jejunum or caecum sampled from slaughtered pigs. Incubating with small intestinal contents, lactic acid was the only fermentation product. Fermentability was highest for chicory roots, followed by wheat bran and sugar beet pulp, while corn cobs were not fermented. Based on SCFA formed in the incubations with caecal contents, ranking of the fermentability of the fibre substrates was in the same order. The effect of adding different fibre substrates to diets of newly weaned piglets on bacteriological and morphological aspects of the gastrointestinal tract was also investigated. In Experiment 1 three groups of five piglets, weaned at four weeks of age, received a control feed (C), C supplemented with corn cobs (50 g/kg) or with chicory roots (20 g/kg). In Experiment 2, diet C was supplemented with sugar beet pulp (120 g/kg) or with wheat bran (75 g/kg). After three weeks animals were euthanized and digesta were sampled from stomach, proximal and distal jejunum, caecum and colon. Furthermore, mucosal scrapings were prepared and tissue samples were taken from jejunum, caecum and colon. Viscosity was determined for jejunal, caecal and colon contents. Corn cobs in the feed increased the number of total bacteria, lactobacilli and bifidobacteria in the stomach and proximal duodenum, while a decreased count of streptococci in distal jejunum contents was noted. Chicory roots increased the counts of Escherichia coli in the distal jejunum and on the mucosa, while sugar beet pulp decreased the number of lactobacilli on the mucosa only. Wheat bran seemed to increase the count of E. coli in jejunal digesta and on the mucosa, and also the number of lactobacilli in the stomach and jejunum. Bifidobacterial numbers were increased but only in the proximal part of the jejunum. Fibre substrates affected the concentration of lactate and SCFA in different parts of the intestinal tract. Feeding corn cobs increased villus length in the proximal jejunum by 13%. The number of intra-epithelial lymphocytes in the villous epithelium of proximal and distal jejunum was decreased by corn cobs and chicory roots supplementation while beet pulp and wheat bran had the opposite effect. In Experiment 1, apoptotic index of the mucosa of the distal jejunum was very low and decreased when corn cobs were fed. Mitotic index in the crypts was only affected by the wheat bran diet and a small decrease was noted. It was concluded that the fermentability of fibre was not an ideal criterion for predicting its effects on the flora. The effect of fibres on viscosity of digesta was negligible probably explaining the lack of clear and consistent influences on the intestinal mucosa.     

In vitro study on gas generation and prebiotic effects of some carbohydrates and their mixtures

This study was carried out to examine the effect of inulin (IN), fructooligosaccharide (FOS), polydextrose (POL) and isomaltooligosaccharides (ISO), alone and in combination, on gas production, gas composition and prebiotic effects. Static batch culture fermentation was performed with faecal samples from three healthy volunteers to study the volume and composition of gas generated and changes in bacterial populations. Four carbohydrates alone or mixed with one another (50:50) were examined. Prebiotic index (PI) was calculated and used to compare the prebiotic effect. The high amount of gas produced by IN was reduced by mixing it with FOS. No reduction in gas generation was observed when POL and ISO mixed with other substrates. It was found that the mixture of IN and FOS was effective in reducing the amount of gas produced while augmenting or maintaining their potential to support the growth of bifidobacteria in faecal batch culture as the highest PI was achieved with FOS alone and a mixture of FOS and IN. It was also found that high volume of gas was generated in presence of POL and ISO and they had lower prebiotic effect. The results of this study imply that a mixture of prebiotics could prove effective in reducing the amount of gas generated by the gut microflora.     

Selected culturable enteric bacterial populations are modified by diet acidification and the growth promotant Tylosin

AIMS: To determine the effect of diet acidification and an in-feed antibiotic growth promotant (Tylosin, Ty) on selected culturable bacterial populations in the gastrointestinal tract (GIT) of mice. METHODS AND RESULTS: Female C57Bl mice were given a standard diet supplemented with Acid Pak (AP) or Ty in the drinking water. After 21 days, lumen and adherent populations of Enterobacteriaceae, enterococci/streptococci, and lactic acid bacteria (LAB) from the ileum, caecum, colon and faeces were enumerated. General intestinal health was assessed by the frequency of haemolytic bacteria in the different intestinal compartments. Contrary to expectations, AP and Ty significantly increased haemolytic bacteria in the lumen of the caecum and colon (P<0.05). The small but significant growth-enhancing effect of Ty (P<0.05) was associated with decreases in enterococci/streptococci and surprisingly, LAB, as well as increases in coliforms. AP, which failed to improve growth rates, reduced coliforms, had limited effects on enterococci/streptococci, and specifically failed to promote the growth of LAB populations in all intestinal compartments. Ty supplementation was also associated with a significant increase in macrolide-resistant enterococci throughout the GIT. CONCLUSIONS: Dietary acidification is less effective than Ty in modulating the population dynamics of selected culturable populations of enteric bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: The mouse can provide a useful experimental model to examine the effects of new dietary supplements, formulations or regimes on changes in microbial population dynamics, including monitoring for antibiotic resistance.     

Investigating the prebiotic and gas-generating effects of selected carbohydrates on the human colonic microflora

AIMS: To compare the fermentation of dietary carbohydrates with reference to their prebiotic and gas-generating capacity. METHODS AND RESULTS: Static anaerobic batch culture fermentations were carried out measuring gas generation and the prebiotic effect of five selected substrates (including various fructo-oligosaccharides, levan and maltodextrin). The largest gas producer was levan, whilst those showing no significant difference to Actilight included oligofructose and maltodextrin. Gas composition data showed that hydrogen and carbon dioxide were the two most quantitatively important gases. The substrate that appeared to have the best prebiotic effect in vitro was branched chain fructo-oligosaccharide (FOS), followed by oligofructose, Actilight and maltodextrin which each exerted a similar effect. The substrate with the least bifidogenic effect was levan. CONCLUSIONS: The composition and total gas generation data showed that there was much variation between and within donor inocula. Generally, the lower gas producers had a more selective fermentation whilst larger gas producers were less specific. SIGNIFICANCE AND IMPACT OF THE STUDY: The study of these three parameters enabled a more complete picture of carbohydrate breakdown to be drawn and hence highlighted the need for potential prebiotics to be more extensively evaluated in order to reduce negative side-effects such as gas distension.     

Effects of deoxycorticosterone acetate on the electrical properties of rat large intestine: segmental differences

The functional heterogeneity of different segments of the rat large intestine was investigated by means of transepithelial potential difference (PD), short-circuit current (Isc) and transepithelial resistance (Rt) measurements in control rats and after deoxycorticosterone acetate (DOCA) pretreatment. Rt and PD were low in caecum and proximal colon but higher in the distal colon and rectum. Isc was highest in the distal colon, lower in the caecum, proximal colon, and rectum. None of the electrical properties was sensitive to amiloride in control conditions. DOCA increased PD and Isc in the caecum, distal colon and rectum but had no effect in the proximal colon. The increase of the Isc after DOCA in the distal colon and rectum was reached by induction of the amiloride-sensitive Isc associated with reduction of the amiloride-insensitive Isc. The effect of DOCA could be completely prevented by concurrent spironolactone treatment. The results suggest that the epithelia of the proximal parts of the large intestine are "leaky" whereas those of the distal colon and rectum are relatively "tight". It is concluded that there is a marked quantitative and qualitative segmental heterogeneity along the rat large intestine.     

Comparison of the in vitro bifidogenic properties of pectins and pectic-oligosaccharides

AIMS: To compare the in vitro fermentation properties of pectins and oligosaccharides derived from them in pure and mixed faecal cultures. METHODS AND RESULTS: Specific growth rates of selected bacterial genera were calculated in pure culture. Bifidobacterium angulatum, B. infantis and B. adolescentis had higher growth rates on pectic oligosaccharides (POS I) derived from high methylated pectin (HMP) than on HMP and B. pseudolongum and B. adolescentis on pectic oligosaccharides (POS II) derived from low methylated pectin than on HMP. Controlled pH batch mixed faecal cultures were then carried out and a prebiotic index was calculated as a mean to compare the fermentation properties of the different substrates. In general, greater fermentation selectivity was obtained with lower degrees of methylation (PI24(-HMP) = -0.11, PI24(-LMP) = 0.033; PI24(-POS I) = 0.071 and PI24(-POS II) = 0.092). An effect of size on prebiotic potential was observed, with the oligosaccharides having more selective fermentation properties than the pectins they derived from. CONCLUSIONS: The degree of methylation plays an important role in the fermentation properties of pectins. Pectic-oligosaccharides are a better prebiotic candidate than the pectins, although their bifidogenic effect is low compared to oligofructose. SIGNIFICANCE AND IMPACT OF THE STUDY: The effect of size on prebiotic potential was demonstrated. Non-selectively fermented polysaccharides like pectin can have their bifidogenic properties improved by partial hydrolysis.     

Unidirectional fluxes of short-chain fatty acids across segments of the large intestine in pig,sheep and pony compared with guinea pig

Unidirectional fluxes of short-chain fatty acids across pig, sheep and pony caecum, proximal and distal colon were studied under short-circuit current conditions in Ussing chambers. Findings are compared with results from guinea pig. Marked species differences are apparent; highest mucosal-to-serosal fluxes of acetate, propionate and butyrate were seen in guinea pig, lower values in pig and smallest fluxes in sheep and pony. Segmental differences between caecum, proximal and distal colon exist mainly in guinea pig and are less developed in pig, sheep and pony. Inhibition of Na⁺/H⁺ exchange by amiloride added to the mucosal solution decreased the mucosal-to-serosal fluxes of short-chain fatty acids clearly in guinea pig caecum and proximal colon, and very little in distal colon. This effect was somewhat less pronounced in pig caecum and distal colon, in caecum and distal colon of sheep and caecum of the pony. In pig, sheep and pony proximal colon and pony distal colon no significant inhibition was observed. Inhibition of the K⁺-H⁺ ATPase by addition of ouabain to the mucosal solution diminished mucosal-to-serosal fluxes of short-chain fatty acids in the guinea pig distal colon extensively. No comparable inhibition was seen in any of the other segments in the animals studied.     

Digesta retention in the gastro-intestinal tract of the orang utan (Pongo pygmaeus)

The diet of the orang utanPongo pygmaeus consists of fruit, leaves, communal insects, and bark, and contains appreciable amounts of non-starch polysaccharides. These complex carbohydrates require microbial fermentation before they can be used as an energy source by the orang utans. The gastrointestinal tract ofP. pygmaeus consists of a simple or unipartite stomach, a relatively long small intestine, and a complex haustrated caecum and colon. This morphology suggests that the capacious proximal colon is the principal site of digesta retention and fermentation of non-starch polysaccharides. We measured several parameters of digesta retention by giving three captive adultP. pygmaeus a pulse dose of inert markers specific for the solute and particulate phases of the digesta and collected their faeces at regular intervals over 192–338 hours. Transit times (times of first appearance of the markers in the faeces) and mean retention times (MRT) were long, consistent with a large complex gastro-intestinal tract. MRTs for the particulate marker were longer (p=0.032) than for the solute marker, indicative of selective retention of large particulate digesta. These results are consistent with the patterns of marker excretion in other mammals that use the digestive strategy of colon fermentation.     

Increased amount of Bifidobacterium thermacidophilum and Megasphaera elsdenii in the colonic microbiota of pigs fed a swine dysentery preventive diet containing chicory roots and sweet lupine

AIMS: To investigate which specific bacterial species that were stimulated or inhibited in the proximal colon of pigs when a fructan-rich diet was compared with a diet that contained resistant carbohydrates. The study focussed especially on Bifidobacterial species by using a noncultureable approach. METHODS AND RESULTS: Terminal restriction fragment length polymorphism (T-RFLP) was used to describe differences in the total colonic microbiota as well as in the populations of Bifidobacterium spp. in pigs fed with a fructan-rich diet and a diet containing resistant carbohydrates. The fructan-rich diet has previously been shown to prevent swine dysentery caused by Brachyspira hyodysenteriae. The T-RFLP profiling, 16S rRNA gene cloning and in situ hybridization showed that the pigs fed with the fructan-rich diet had a higher proportion of Bifidobacterium thermacidophilum subsp. porcinum and Megasphaera elsdenii. CONCLUSIONS: These findings suggested that the bacterial fructan fermentation occurring in the porcine colon might be cross-feeding of lactate produced by B. thermacidophilum and used by M. elsdenii. SIGNIFICANCE AND IMPACT OF THE STUDY: B. thermacidophilum and M. elsdenii may be the course of the inhibition of the pathogenic bacteria Brach. hyodysenteriae in colon of pigs when they are fed fructan-rich diets.     

Aldosterone does not regulate amiloride-sensitive Na(+) transport in the colon of the Australian common brushtail possum,Trichosurus vulpecula

Plasma aldosterone concentrations and the magnitude of amiloride-sensitive Na(+) transport in the proximal and distal colon of newly caught wild possums, and of possums maintained on either low or high Na(+) diets, were determined to evaluate their role in the regulation of salt content of faeces in common brushtail possums. Wild animals had a plasma aldosterone concentration of 439+/-115 pmol l(-1) and high levels of amiloride-sensitive Na(+) transport in both the proximal and distal colon. Animals maintained on a low Na(+) diet for 14 days excreted very little Na(+) in the urine and had an elevated aldosterone concentration (840+/-246 pmol l(-1)), but levels of amiloride-sensitive Na(+) transport in the proximal and distal colon were similar to those in wild animals. Conversely, while provision of a high Na(+) diet (7 days or 14 days) resulted in increased urinary Na(+) excretion and a fall in aldosterone (approximately 250 pmol l(-1)), there was no reduction in the amount of amiloride-sensitive Na(+) transport in either the proximal or distal colon. These data strongly indicate that aldosterone does not regulate amiloride-sensitive Na(+) transport in the colon of possums and that the colon is not involved in the regulation of salt content of the faeces in this species.     

Developing a quantitative approach for determining the in vitro prebiotic potential of dietary oligosaccharides

Prebiotics are nondigestible carbohydrates that beneficially affect the host by selectively stimulating the growth and/or activity of one, or a limited number of, bacteria present in the colon. The selected genera should have the capacity to improve host health (e.g. Bifidobacterium, Lactobacillus). To help identify preferred types, for inclusion into the diet, a quantitative equation [measure of the prebiotic effect (MPE)] is suggested. This will help evaluate, in vitro, the fermentation of dietary carbohydrates and compare their prebiotic effect. Although the approach is not meant to define health values, it is formulated to better inform the choice of prebiotic. It therefore, compares measurements of bacterial changes through the determination of maximum growth rates of predominant groups present in faeces, rate of substrate assimilation and the production of lactic, acetic, propionic and butyric acids. The equation will allow further in vitro comparisons of MPE, leading towards further studies (e.g. in humans) to determine the success of dietary intervention.     

Microscopic and functional anatomy of the ileal papilla and caecocolonic valve in the rat.

In the rat, topographic and X-ray studies of the caecum and ascending colon, together with microscopic anatomic observations of the ileal papilla and caecocolonic valve, showed that junction structures contribute to prevent the backflow of the caecal content into the ileum and to direct the ileal content within the caecum whatever the various positions of the caecum in the abdominal cavity.     

Digestive strategy of the south-east African lesser bushbaby, Galago moholi

Galago moholi is a small nocturnal primate, which has a specialised diet of Acacia exudate and insects. Both exudate and insect exoskeletons contain beta-linked polysaccharides that can be used as an energy source by mammals via microbial fermentation. The morphology of the gastro-intestinal tract of G. moholi suggests that the complex, elongate caecum, proximal colon and ansa coli are most likely to be the fermentation compartment. The results of a digesta marker study showed that there was selective retention of the fluid phase of the digesta, a pattern commonly seen in small caecum-fermenting mammals. There was also retention of the particle marker in the gastro-intestinal tract. Comparison to these results with those from other mammals, including other bushbaby species, suggests that this was due to retention of particulate digesta in both the stomach and the ansa coli, a U-shaped loop in the proximal colon. The digestive strategy of the south-east African lesser bushbaby is best described as caeco-ansal fermentation, as the caecum, proximal colon and ansa coli function as distinct fermentation chambers. However, we contend that, because it is soluble polysaccharides in exudates travel with the fluid phase of the digesta, reach the hindgut sooner than particles of the insect exoskeleton, and are fermented faster than particulate digesta, that lesser bushbabies, in spite of their small size (approximately 200 g) are able to include an apparently low-quality food (exudate) in their diet.     

Biological properties of fructooligosaccharides with different contents of kestose and nystose in rats

In a four-week experiment on rats' diets containing 5% of sucrose or fructooligosaccharides (FOS) diversified in terms of kestose and nystose contents: 6:1 (FOS-K), 3:1 (FOS-KN), and 0.5:1 (FOS-N) were applied. All FOS preparations, primarily FOS-N, considerably increased the mass of caecum, lowered pH of caecal digesta, and increased concentrations of protein. The glycolytic activity of the caecal digesta was generally alike in all groups, except for the control group where the activity of beta-glucosidase was negligibly lower and that of alpha-galactosidase higher. The administration of FOS preparation with a diet increased the concentration and the pool of total VFA in the caecal digesta, especially in the case of butyric and propionic acids and decreased the concentration of iso-butyric and valeric acids. When compared with the kestose-rich preparation, the nystose-rich preparation increased the production of total VFA in the caecum, primarily of n-butyrate and propionate. Different length of kestose and nystose chains had no effect on the activity of bacterial enzymes in the caecum nor the biochemical indices of serum, concentration of cholesterol, glucose, urea, Ca, P and Mg.     

Comparison of the bacterial community structure within the equine hindgut and faeces using Automated Ribosomal Intergenic Spacer Analysis (ARISA)

The horse’s hindgut bacterial ecosystem has often been studied using faecal samples. However few studies compared both bacterial ecosystems and the validity of using faecal samples may be questionable. Hence, the present study aimed to compare the structure of the equine bacterial community in the hindgut (caecum, right ventral colon) and faeces using a fingerprint technique known as Automated Ribosomal Intergenic Spacer Analysis (ARISA). Two DNA extraction methods were also assessed. Intestinal contents and faeces were sampled 3 h after the morning meal on four adult fistulated horses fed meadow hay and pelleted concentrate. Irrespective of the intestinal segment, Principal Component Analysis of ARISA profiles showed a strong individual effect (P<0.0001). However, across the study, faecal bacterial community structure significantly (P<0.001) differed from those of the caecum and colon, while there was no difference between the two hindgut communities. The use of a QIAamp® DNA Stool Mini kit increased the quality of DNA extracted irrespective of sample type. The differences observed between faecal and hindgut bacterial communities challenge the use of faeces as a representative for hindgut activity. Further investigations are necessary to compare bacterial activity between the hindgut and faeces in order to understand the validity of using faecal samples.