Large Intestine Of Pigs Research Articles

Influence of differing carbohydrate sources on l-tryptophan metabolism by porcine fecal microbiota studied in vitro

Four types of carbohydrate sources, sugar beet pulp (SBP), rye grass hay (RYE), alfalfa hay (ALF) and fructooligosaccharides (FOS) were used to investigate their effects on the metabolism of l-tryptophan to skatole and indole by a mixed bacterial population from the large intestines of pigs. Microbial suspensions were anaerobically incubated at 38 °C, and indole compounds, pH value and volatile fatty acids were analyzed after 24 h fermentation. Effects of carbohydrate sources on the microbial diversity were analyzed using denaturing gradient gel electrophoresis (DGGE) of PCR amplicons of 16S rDNA, cloning and sequencing. Addition of SBP showed decreasing effect on skatole concentration and decreased the relative rate of skatole production significantly, whereas RYE and ALF treatments significantly increased skatole concentration and the relative rate of skatole production. The rate of tryptophan degradation was reduced by addition of ALF remarkably. For the FOS group, skatole concentration and relative rate of skatole production were both significantly reduced. Total and individual VFAs (acetate, propionate, butyrate and valerate) were significantly higher in the four carbohydrate-added groups than in the none-added. Additions of SBP, RYE, ALF and FOS in pig fecal slurries with l-tryptophan markedly decreased the culture medium pH values. The DGGE profiles showed differences between cultures with different carbohydrate substrates, though some bands were common to all cultures. Fermentation with SBP showed a higher bacterial diversity than with others, with three distinct bands appeared. Sequences of the corresponding 16S rRNA of two bands were related to Eubacterium rectale (94%) and Clostridium sp. (96%), respectively. Three bands were present only in SBP, RYE and ALF samples. Two of these three bands represented 93 and 98% similarity to Lachnospira pectinoschiza and Clostridium disporicum DSM 5521, respectively. These results suggested that the reduced concentration of skatole observed in the presence of SBP and FOS may be caused by decreased tryptophan degradation to indolic compounds and by shifted microbial metabolism of tryptophan toward indole production at the expense of skatole, resultant from the changed microbial ecosystem and pH value. The bacteria C. disporicum DSM 5521 may play a role in the production of skatole.

A Review of Interactions between Dietary Fiber and the Gastrointestinal Microbiota and Their Consequences on Intestinal Phosphorus Metabolism in Growing Pigs

Dietary fiber is an inevitable component in pig diets. In non-ruminants, it may influence many physiological processes in the gastrointestinal tract (GIT) such as transit time as well as nutrient digestion and absorption. Moreover, dietary fiber is also the main substrate of intestinal bacteria. The bacterial community structure is largely susceptible to changes in the fiber content of a pig's diet. Indeed, bacterial composition in the lower GIT will adapt to the supply of high levels of dietary fiber by increased growth of bacteria with cellulolytic, pectinolytic and hemicellulolytic activities such as Ruminococcus spp., Bacteroides spp. and Clostridium spp. Furthermore, there is growing evidence for growth promotion of beneficial bacteria, such as lactobacilli and bifidobacteria, by certain types of dietary fiber in the small intestine of pigs. Studies in rats have shown that both phosphorus (P) and calcium (Ca) play an important role in the fermentative activity and growth of the intestinal microbiota. This can be attributed to the significance of P for the bacterial cell metabolism and to the buffering functions of Ca-phosphate in intestinal digesta. Moreover, under P deficient conditions, ruminal NDF degradation as well as VFA and bacterial ATP production are reduced. Similar studies in pigs are scarce but there is some evidence that dietary fiber may influence the ileal and fecal P digestibility as well as P disappearance in the large intestine, probably due to microbial P requirement for fermentation. On the other hand, fermentation of dietary fiber may improve the availability of minerals such as P and Ca which can be subsequently absorbed and/or utilized by the microbiota of the pig's large intestine.

PH gradients and a mirco-pore filter at the luminal surface affect fluxes of propionic acid across guinea pig large intestine

A neutral pH microclimate had been shown at the luminal surface of the large intestine. The aim was to estimate to what extent fluxes of propionic acid/propionate are affected by changes of the luminal pH when this microclimate is present, largely reduced or absent. Fluxes of propionic acid/propionate (J(Pr)) across epithelia from the caecum, the proximal and the distal colon of guinea pigs were measured in Ussing chambers with and without a filter at the luminal surface. With bicarbonate and with a neutral or an acid pH of mucosal solutions (pH 7.4 or 6.4), mucosal-to-serosal fluxes (J(ms)(Pr) ) were 1.5 to 1.9-fold higher at the lower pH, in bicarbonate-free solutions and carbonic anhydrase (CA) inhibition 2.1 to 2.6-fold. With a filter at the mucosal surface and with bicarbonate containing solutions, J (ms) (Pr) was not or only little elevated at the lower pH. Without bicarbonate J(ms)(Pr) was clearly higher. We conclude that the higher J(ms)(Pr) after luminal acidification is due to vigorous mixing in Ussing chambers resulting in a markedly reduced unstirred layer. Therefore, an effective pH microclimate at the epithelial surface is missing. J(ms)(Pr) is not or is little affected by lowering of pH because in the presence of bicarbonate the filter maintains the pH microclimate. However, in bicarbonate-free solutions J(ms)(Pr) was higher at pH 6.4 because a pH microclimate does not develop. Findings confirm that 30-60% of J(ms)(Pr) results from non-ionic diffusion.

Kinetics of enzymatic digestion of feeds as estimated by a stepwise in vitro method

Nutritional feed values are currently based on aggregate criteria such as the ileal or faecal digestibility. Digestibility is the result of several processes including hydrolysis, absorption, secretion and passage. In order to develop mechanistic models of digestion to be used for feed evaluation, these processes have to be quantified. The aim of the current study was to determine the enzymatic hydrolysis (or: in vitro digestion) kinetics of main constituents (organic matter, nitrogen and starch) in wheat, barley, wheat bran and soybean meal, using a three-step, enzymatic in vitro method that mimics digestion in the stomach, small and large intestine of pigs. The in vitro results were compared with in vivo results. Hydrolysis kinetics ( i.e., solubilisation of feed constituents) was modelled using an exponential segmented model estimating the extent and rate of digestion for each enzymatic digestion step. In vitro digestion of organic matter of soybean meal occurred mainly through the action of pepsin (0.67 versus <0.30 for other feeds, P<0.05), which was caused by the enzymatic digestion of protein at this site. Organic matter of cereals was mainly hydrolysed by enzymes mimicking digestion in the small intestine, and was mainly caused by starch digestion. Fractional in vitro digestion rates of organic matter were higher in the stomach than in the small intestine for cereals (0.20–0.34 min −1 versus 0.02–0.15 min −1, P<0.05). The potential in vitro digestibility of organic matter was nearly 0.88 for wheat and soybean meal, 0.79 for barley and 0.61 for wheat bran, which correspond to typical in vivo digestibility values. The in vitro digestibility corresponded reasonably well to in vivo results for enzyme systems mimicking ileal and total tract digestion. The results of this study indicate that it is possible to quantify dynamic aspects of digestion of feedstuffs fed to non-ruminant animals.

Influence of purified dietary fibre on bacterial protein synthesis in the large intestine of pigs, as measured by the gas production technique

Abstract Microbial fermentation of non-digestible carbohydrates in the pig's large intestine induces a shift of N excretion from urea in urine to bacterial protein in faeces. Experiments were carried out to measure the mineral N incorporation by the pig intestinal microflora using 5 purified carbohydrates in a gas-test: starch (S), cellulose (C), inulin (I), pectin (P) and xylan (X). Fermentation kinetics was modelled. N source in the buffer solution was replaced by 15 N labelled NH 4 Cl. The bacterial N fixation was determined at mid-fermentation, measuring 15 N incorporation into the solid phase of the buffer. The bacterial N fixation was higher ( P − 1 ) and C (0.074 h − 1 ) showed lower half time fractional rate of degradation than S (0.153 h − 1 ), P (0.133 h − 1 ) and X (0.104 h − 1 ). The insoluble dietary fibre content of the substrates was negatively correlated to bacterial N fixation ( r = − 0.957, P = 0.011). The high crude protein content of P (32.5 mg g − 1 DM) might explain the lower impact of this substrate on bacterial N fixation, despite its rapid fermentation. Beside the proportion of insoluble fibre, the N content and the rate of fermentation seem to be the major factors influencing bacterial protein synthesis. Further studies including ingredients with variable content of indigestible protein and mean retention time in the pig's intestines are necessary.

A step-wise in vitro method to estimate kinetics of hydrolysis of feeds

Abstract Nutritional feed values are currently based on aggregate criteria such as the ileal or faecal digestibility. Digestibility is the result of two competing processes: digestion and passage. In order to develop mechanistic models of digestion to be used for feed evaluation, both processes have to be quantified. The aim of this study was to determine the hydrolysis kinetics of main constituents (organic matter, N and starch) in wheat, barley, wheat bran and soybean meal, using a three-step, enzymatic in vitro method mimicking digestion in the stomach, small and large intestine of pigs. Kinetics of hydrolysis (i.e. solubilisation of feed constituents) was modelled using an exponential segmented model estimating the extent and rate of digestion in each digestive segment. Digestion of organic matter of soybean meal occurred mainly in the stomach (67% vs. in vivo digestibility values. The results of the present study allow characterising different feeds with the objective to model the digestion process in pigs.

Identification of a Novel, Invasive, Not-Yet-Cultivated Treponema sp. in the Large Intestine of Pigs by PCR Amplification of the 16S rRNA Gene

Laser capture microdissection in combination with fluorescent in situ hybridization was used to identify an unknown species of spirochetes from the pig colonic mucosa. The 16S rRNA gene was PCR amplified, and the closest related type strain was Treponema bryantiiT (90.1%). The spirochete, here named "Candidatus Treponema suis," was associated with colitis, including invasion of the surface epithelium as well as superficial parts of the mucosa.

The effect of dietary carbohydrates and Trichuris suis infection on pig large intestine tissue structure, epithelial cell proliferation and mucin characteristics

Two experiments (Exps. 1 and 2) were performed to study the influence of Trichuris suis infection and type of dietary carbohydrates on large intestine morphology, epithelial cell proliferation and mucin characteristics. Two experimental diets based on barley flour were used; Diet 1 was supplemented with resistant carbohydrates from oat hull meal, while Diet 2 was supplemented with fermentable carbohydrates from sugar beet fibre and inulin. In Experiment 1, 32 pigs were allocated randomly into four groups. Two groups were fed Diet 1 and two groups Diet 2. Pigs from one of each diet group were inoculated with a single dose of 2000 infective T. suis eggs and the other two groups remained uninfected controls. In Experiment 2, 12 pigs were allocated randomly into two groups and fed Diet 1 or Diet 2, respectively, and inoculated with a single dose of 2000 infective T. suis eggs. All the pigs were slaughtered 8 weeks post inoculation (p.i.). The worm counts were lower in pigs fed Diet 2 in both experiments, but not significantly so. Both diet and infection status significantly influenced the tissue weight of the large intestine. In both experiments, pigs fed Diet 2 had heavier large intestines than pigs fed Diet 1 and in Experiment1 the infected pigs of both diets had heavier large intestines than their respective control groups. Diet and infection also significantly affected the morphological architecture and mucin production in both experiments. Pigs fed Diet 1 had larger crypts both in terms of area and height than pigs fed Diet 2 and T. suis infected pigs on both diets in Experiment 1 had larger crypts than their respective control groups. The area of the mucin granules in the crypts constituted 22–53% of the total crypt area and was greatest in the T. suis infected pigs fed Diet 1. Epithelial cell proliferation was affected neither by diet nor infection in any of the experiments. The study showed that both T. suis infection and dietary carbohydrates significantly influence the morphological architecture and the production and composition of mucins in the large intestine of pigs and suggests that both factors are important in large intestine function and that carbohydrates may play a role in the susceptibility to intestinal helminth infections.

Flavor Improvement in Pork from Barrows and Gilts via Inhibition of Intestinal Skatole Formation with Resistant Potato Starch

Skatole originates from microbial processing of tryptophan in the large intestine of pigs and accumulates in adipose tissue. Formation may be inhibited by the anti-apoptotic function of butyrate formed out of raw potato starch. Two groups of pigs (each consisting of gilts and barrows) were fed from 30 to 110 kg life weight either a conventional diet (controls; n = 35) or an isocaloric diet containing 300 g of raw potato starch/kg of body weight (RS; n = 34). Skatole concentrations were measured in colon content, blood, and adipose tissue. Odor of cooked meat samples was evaluated by a test panel. RS reduced concentrations in colon content and blood plasma (P < 0.001). Back fat concentrations were decreased significantly from 25 to 1.40 ng/g (barrows; P < 0.001) and from 40 to 9 ng/g (gilts; P < 0.001). Odor rating (scale of 1-5 from very unpleasant to very pleasant) was 3.07 for low skatole concentrations and 2.66 for both medium and high skatole concentrations (P < 0.05).

The Effect of Source of Dietary Fiber and Starch on Ileal and Fecal Amino Acid Digestibility in Growing Pigs

Studies were carried out with a repeated 4x4 Latin square design with eight cannulated pigs fed four experimental diets to investigate the effect of dietary fiber and starch sources on apparent ileal and fecal amino acid digestibility. Each period lasted 15 d, with diet acclimation from d 1 to 7, feces collection for 48 h on d 8 to 9 and ileal sample collection for 12 h on d 13 to 15. The four experimental diets consisted mainly of cooked rice with the addition of protein sources (CON), partial replacement of cooked rice with either potato starch (PS), sugar beet pulp (SBP) or wheat bran (WB). Chromic oxide was used as an indigestible marker. With the exception of histidine, lysine and tryptophan, no differences were observed in the apparent ileal digestibility of amino acids between diets. The inclusion of potato starch did not affect the ileal and fecal amino acid digestibility. In comparison with diet CON, a decreased (p<0.05) ileal digestibility of histidine was found in pigs fed diet SBP, while the ileal digestibilities of histidine, lysine and tryptophan were decreased (p<0.05) by the inclusion of wheat bran. Inclusion of fiber sources (sugar beet pulp and wheat bran) caused a reduction (p<0.05) in the fecal amino acid digestibility and the net disappearance of amino acids in the large intestine. Of the indispensable amino acids, there was a 'net synthesis' for methionine in the large intestine of pigs when diets were supplemented with dietary fiber. The decrease in fecal amino acid digestibility with the addition of dietary fiber indicates an increase in the synthesis of bacterial protein in the large intestine.

Effect of inoculum and pepsin–pancreatin hydrolysis on fibre fermentation measured by the gas production technique in pigs

Two experiments were undertaken to adapt the in vitro gas production technique in syringes, used for ruminants, to fibre fermentation studies in the large intestine of pigs. In a first experiment, two inocula (faeces and large intestine content) were compared at four dilution levels in a buffer solution (0.025, 0.05, 0.1 and 0.2 g ml −1) with two substrates: wheat bran and sugar–beet pulp. The accumulated gas produced over 72 h was modelled and the kinetics parameters compared. The time to half asymptote was lower for the intestinal inoculum (5.5 versus 8.0 h, P<0.02), but the 2 inocula yielded similar fractional rates of degradation (0.16 h −1) and gave equal final gas production (252 ml g −1 substrate). No interaction (P>0.05) was observed between inocula and substrates. The dilution of the samples in the buffer solution increased (P<0.001) the lag time (from 0.9 to 2.1 h for dilution rates ranging from 0.2 to 0.025 g ml −1, respectively) and decreased (P<0.001) the rates of substrate degradation (from 0.18 to 0.13 h −1). A second experiment aimed to study the effect of an in vitro pepsin–pancreatin hydrolysis of the sample prior to the gas test. Six substrates were tested: maize, wheat bran, sugar–beet pulp, lupins, peas and soybean meal. The enzymatic hydrolysis affected (P<0.001) the kinetics parameters and the ranking order of the fermented substrates. The lag times also increased for all ingredients. The rate of degradation decreased when peas, lupins, maize and wheat bran were hydrolysed (P<0.001) but it increased with soybean meal (P=0.014) and sugar–beet pulp (P<0.001). Final gas production increased with peas and soybean meal (P<0.001), remained unchanged for lupins and decreased for the other substrates (P<0.001). In conclusion, the method using faeces as a source of microbial inoculum is reliable to characterise the fermentation kinetics of ingredients in the large intestine of pigs. However, it is important to hydrolyse the substrates with pepsin and pancreatin before the gas tests.

Lawsonia intracellularisinfection in the large intestines of pigs

In this study we examined the proliferative enteropathy, caused by the obligate intracellular bacterium Lawsonia intracellularis, in colon of naturally infected pigs, using immunohistochemistry, in situ hybridisation and scanning confocal laser microscopy. When 396 pigs submitted for routine laboratory examination were investigated, large intestinal gross lesions were seen in 93, including 74 cases of L. intracellularis colitis (proliferative enteropathy). Fifty-one pigs without recorded colonic gross lesions revealed L. intracellularis colitis microscopically. In four cases, L. intracellularis was only revealed in colon. Fifty-seven pigs were positive for L. intracellularis in the small intestines only. Thus, the overall prevalence of colonic infection in L. intracellularis-positive animals was as high as 69% (125 out of 182). In comparison, the large intestinal pathogens Brachyspira hyodysenteriae and Salmonella enterica were only isolated from 5 and 4 of the 93 cases, respectively. Morphologically, an unforeseen severe involvement of the subepithelial mucosa with multiple L. intracellularis found free and within large macrophages was observed in areas with acute infection. The distribution of whole L. intracellularis organisms was confirmed by in situ hybridisation and scanning confocal laser microscopy. The significance and possible role of subepithelial infection in the proliferative enteropathy is discussed. In conclusion, the study shows that L. intracellularis is a prevalent cause of naturally acquired colitis in pigs.

Transport of bacteria across and along the large intestinal lumen of guinea pigs

Flow cytometry was used to observe the transport of fluorescently labelled viable bacteria in the large intestinal lumen of guinea pigs after the injection of the bacteria into the proximal colon. Bacteria were transported along the radial and longitudinal axes of the intestine and were separated from dietary residue, accumulated, and then transported back to the caecum. These observations, together with the heterogeneous distribution of bacterial species and chemical composition across and along the large intestine, suggest that there are several different microenvironments within the intestinal lumen between which bacteria and/or dietary residues move. The existence of different microenvironments within the intestinal lumen is consistent with poor mixing of the digesta within the large intestine of pigs and chickens.

GAL‐ and VIP‐Immunoreactive Nerve Structures in the Ileum and Large Intestine of Pigs with Dysentery

The morphology, neurochemistry and function of intramural nerve structures in the mammalian gastrointestinal tract are relatively well known, but in normal, healthy individuals. The present study was aimed at investigating the chemical coding of nerve structures in the wall of the ileum and large intestine in normal pigs (n = 3) and in pigs undergoing dysentery (n = 6). Dysentery was evoked by artificial infection of the clinically healthy animals per os with Brachyspira hyodysenteriae. All the animals were deeply anaesthetized and transcardially perfused with 4% paraformaldehyde. The cryostat sections of the intestines were processed for double‐labelling immunohistochemistry using antisera against PGP 9.5, GAL and VIP. In the intramural plexuses of the control pigs, the percentage of GAL‐immunoreactive (GAL‐IR) perykarya varied from 11% (descending colon) to 19% (centrifugal turns of the ascending colon) whereas in the dysenteric pigs, it was distinctly higher, reaching from 28% (ileum) up to 48% (cecum). In the control animals, the percentage of VIP‐IR neuronal somata varied from 3% (descending colon) to 19% (ileum). In dysenteric pigs, it was from 6% (descending colon) up to 28% (cecum). In the muscular coat (MC) and mucous membrane (MM) of the normal intestine, very numerous GAL‐ and VIP‐IR nerve fibres were observed. The nerve fibres in the myenteric plexus (MP) were even more numerous than those in the muscular coat while in the outer (OSP) and inner (ISP) submucous plexuses, they were less abundant. In the dysenteric pigs, the nerve fibres found in MC, MP and OSP were less numerous, whereas those observed in ISP and MM were more abundant than those in the control animals. The present results suggest that GAL and VIP are involved in the regulation of inflammatory processes developing in the porcine gastrointestinal tract during dysentery.

Butyrate and propionate production from D-mannitol in the large intestine of pig and rat

Butyrate and propionate production from D-mannitol in the large intestine of pig and rat

Effect of feed particle size and feed processing on morphological characteristics in the small and large intestine of pigs and on adhesion of Salmonella enterica serovar Typhimurium DT12 in the ileum in vitro1

A 2 x 2 factorial experiment with pigs was undertaken to investigate the effect of particle size (fine and coarse) and feed processing (pelleted and nonpelleted) on morphological characteristics in the small intestine, cecum, and colon of pigs and on the adhesion of Salmonella enterica serovar Typhimurium DT12 to the ileum in vitro. Ninety-six pigs (average BW = 33 +/- 7 kg) were fed the experimental diets. After 4 wk, 24 pigs were selected (six pigs per diet) and euthanized, and tissue samples were taken from the mid and distal small intestine, cecum, and distal colon. The effects of particle size and feed processing on villus height and crypt depth in the small intestine were minor. Feeding coarse diets increased (P = 0.05) the crypt depth in the colon. The crypt depth was 420 +/- 12 and 449 +/- 12 microm in pigs fed finely and coarsely ground feed, respectively. Pigs fed pelleted diets had a larger (P = 0.01) staining area for neutral mucins, as well as for acidic and sulfomucins on the villi of the distal small intestine than pigs fed nonpelleted diets. The area was 41, 46, and 33% larger for neutral, acidic, and sulfomucins, respectively. The mucin-staining areas of the crypts in the cecum and the colon were not affected by the experimental diets. Examination of lectin binding characteristics of the distal small intestine and the cecum did not reveal any differences between the experimental diets. Using a pig intestine organ culture model, Salmonella adhered less (P < 0.05) to the ileal tissue of pigs fed the nonpelleted diets than to those fed pelleted diets; the adherence was 60% less in these pigs. Results of this study suggest that pigs fed pelleted diets secrete mucins that are capable of binding Salmonella enterica serovar Typhimurium DT12 and thereby allowing for colonization. Therefore, pigs fed a nonpelleted diet are better protected against Salmonella infections than pigs fed a pelleted diet.

Odour from animal production facilities: its relationship to diet

Though bad odour has always been associated with animal production, it did not attract much research attention until in many countries the odour production and emission from intensified animal production caused serious nuisance and was implicated in the health problems of individuals living near animal farms. Odour from pig production facilities is generated by the microbial conversion of feed in the large intestine of pigs and by the microbial conversion of pig excreta under anaerobic conditions and in manure stores. Assuming that primary odour-causing compounds arise from an excess of degradable protein and a lack of specific fermentable carbohydrates during microbial fermentation, the main dietary components that can be altered to reduce odour are protein and fermentable carbohydrates. In the present paper we aim to give an up-to-date review of studies on the relationship between diet composition and odour production, with the emphasis on protein and fermentable carbohydrates. We hypothesise how odour might be changed and/or reduced by altering the diet of pigs. Research so far has mainly focused on the single effects of different levels of crude protein and fermentable carbohydrates on odour production. However, also important for odour formation are the sources of protein and fermentable carbohydrates. In addition, it is not only the amount and source of these compounds that is important, but also the balance between them. On the basis of our review of the literature, we hypothesise that odour nuisance from pig production facilities might be reduced significantly if there is an optimum balance between protein and fermentable carbohydrates in the diet of pigs.

Estimation of protein fermentation in the large intestine of pigs using a gas production technique

Proteolytic fermentation in the colon of pigs and the caecum of poultry can have negative effects on their performance and health due to formation of harmful end products. To reduce this, rations can be formulated with expected carbohydrate fermentation being higher in level, and rate, than that of protein fermentation, as it is accepted that available energy is the limiting factor during fermentation in the hindgut. In this study, a modified version of a gas production technique was used to determine fermentation characteristics of protein in feedstuffs and concentrates after pre-digestion with pepsin and pancreatic enzymes in order to simulate digestion in the stomach and small intestine of pigs. Completing the incubations in an N-free environment, and with an excess of rapidly fermentable carbohydrates, made N the limiting factor to microbial growth, and so gas production profiles reflect availability of N. Results showed that fermentation of protein in the hindgut can be determined with this modified gas production technique, and that there were distinct differences in protein fermentation among the feed samples. Availability of protein for fermentation was highest in pea meal, solvent extracted soybean meal and feather meal, and lowest in palm kernel (expeller), wheat grain and meat meal. Between 5 and 15 h of incubation, gas production increased linearly. Urea was used as a positive control, as it is readily available to microbes. Gas production after 10 h of incubation, relative to gas production with urea, was assumed to be a measure of protein availability, allowing the content and proportion of fermentable crude protein (CP) to be estimated. Results show that this gas production technique ranked feed samples relative to their CP availability in the hindgut. Four concentrates were made with increasing proportions of expected fermentable CP, which was confirmed with the in vitro technique.

Butyrate and propionate production from D-mannitol in the large intestine of pig and rat

Fermentation of D-mannitol and the bacteria responsible for it were analyzed by 13C-NMR spectroscopy and amplified ribosomal restriction analyses (ARDRA) on intestinal bacteria in pig cecal digesta and in a rat in vivo feeding trial. [1-13C]-Mannitol was fermented by pig cecal digesta mainly to [2-13C]-propionate, [3-13C]-propionate, [2-13C]-butyrate, and [4-13C]-butyrate. Dietary D-mannitol at a 5% level induced significantly higher cecal butyrate concentration in the rat model. The evolution of rat fecal bacteria due to feeding with D-mannitol suggested the involvement of a lactate-utilizing butyrate producer, Clostridium indolis, in the stimulation of butyrate production. Rat intestinal microbiota is often difficult to extrapolate to that of humans, but the stimulation of the lactate-utilizing butyrate producers and propionate producers was suggested by the 13C-NMR spectroscopy of the end products of pig cecal fermentation and ARDRA on rat fecal bacteria. These results suggest the potential of D-mannit...

Identification and localisation of the sodium channel alpha subunits carrying the Ttx-sensitive sodium current (INa) in the enteric nervous system of the guinea PIG intestine

The sodium channel protein consists of an alpha subuint in association with auxiliary beta subunits. The 5 neuronal alpha subnnit isoforms that carry the TTX-sensittve current are differentially expressed according to the neuronal types and have different functional properties, which result in distinct conductances in specific cells. Our work was designed in order to identify which alpha subunits carry the TTX-sensitive Na current in the enteric nervous system. Experiments were performed on fixed whole mount preparations of the myenteric and submucous plexuses of guinea pig (GP) small and large intestine using polydonal antibodies (ABs) raised against rat and/or human epitopes of the following alpha subunits : Navl.1, Nay1.2, Navl.3, Navl.6 and Nay1.7. Positive controls on non enteric nervous system were obtained for all ABs except that against Nay1.7. AB selectivity was verified using Western blots performed on rat and GP brain membrane preparations. Only NaV1.2 and Navl.3 alpha subunits were expressed in enteric neurons. NaV1.2 was expressed in the majority of the enteric neurons and immunoreactivity was located in the soma. Interestingly, it was highly expressed in a single axon hillock of the enteric sensory neurons. Some of the myenteric NaV1.2 immunoreactive non-sensory neurons are likely to be motor neurons that innervate the longitudinal muscle. Navl.3-fike immunoreactivity was observed only in descending filamentous neurons It was located in the soma, the long ramifying dendrites and the axon. Numerous smooth nerve fibers were also labeled. These fibres are extrinsic in origin since they enter the gut wall in large bundles running from the mesentery. Using Western blots performed on adult and new born rat and GP brain membrane preparations, the Navl.2 AB, raised against epitopes located in the I-I1 intracellular loop (M1 IL), stained a band at 230 kDa. Using rat brain membrane preparations, the Navl.3 AB, also raised against an epitope located in 1-II 1L, stained a band at 130 kDa. A band of similar low molecular weight was also stained using a Pan AB raised against the loop llI-IV. The expression of both the 230 and 130 kDa protein was age-dependent as previously described for Navl.2 and Navl 3 (Felts eta;. 1997). Our data strongly suggests that in enteric sensory neurons and in some motor neurons of the GP the TTX-sensitive INa is exclusively car'ned by the Navl.2 alpha subunit. This work is supported by GSK and CNRS.