Periodic fluid extrusion and models of digesta mixing in the intestine of a herbivore,the common brushtail possum (<Emphasis Type="Italic">Trichosurus vulpecula</Emphasis>)

The digesta in four gut compartments (proximal and distal halves of small intestine, caecum, and proximal colon) of a wild hindgut fermenting herbivore, the common brushtail possum (Trichosurus vulpecula), were investigated by rheometry and permeametry. Digesta from all compartments were highly viscous and exhibited shear-thinning. Apparent viscosity was positively related to dry matter content, and increased from proximal small intestine to colon. Dynamic rheological measurements showed that in small intestinal digesta the elastic modulus was greater than the viscous modulus and their ratios were characteristic of weak gels, indicating that digesta could sustain compression. The apparent viscosity of distal small intestinal digesta was markedly lower when measured by capillary viscometry than by rotatory viscometry, indicating that plug flow was likely to be facilitated by lubrication from a peripheral layer of less viscous fluid; i.e., there was an augmented plug flow. Permeametry showed that fluid was extruded from all digesta on compression at physiological pressures, that there was significant permeability of proximal and distal small intestinal digesta, but that digesta became progressively compacted during permeation, with a concomitant reduction in permeability as dry matter content increased. It is proposed that conditions within the small intestine differ from those of an ideal plug flow reactor as radial mixing and turbulence cannot occur. Instead, we suggest that segmentation and peristalsis aid radial mixing of the fluid phase by compressing the solid phase, with extrusion of fluid through the digesta plug. This extrusion may be followed by resorption of fluid back into the plug when the elasticity of the solid phase of digesta is Hookean, thus aiding the mixing of secreted enzymes with insoluble substrates within the plug.     

Increased diet viscosity by oat β-glucans decreases the passage rate of liquids in the stomach and affects digesta physicochemical properties in growing pigs

Rheological properties of digesta play a role in digesta passage kinetics through the gastrointestinal tract, in turn affecting nutrient absorption kinetics. Therefore, we studied the effects of diet viscosity on digesta passage and physicochemical properties in pigs. Twenty male growing pigs (35 kg body weight at the start) were assigned to one of five diets with increasing dietary concentrations of β-glucans (BG; from 0 % to 10 %), in exchange for maize starch. After a 17-day adaptation period, pigs were euthanised and the mean retention time (MRT) of digesta solids (TiO₂) and liquids (Cr-EDTA) in the stomach, and proximal and distal half of the small intestine was quantified. In the stomach, the MRT of liquids, but not of solids, increased when dietary BG level increased (6 min per % dietary BG, P = 0.008 and R² = 0.35). Concomitantly, stomach DM content (5 g/kg per % dietary BG, P < 0.001 and R² = 0.53) and apparent digesta viscosity (56 Pa × s at 1/s shear rate per % dietary BG, P = 0.003 and R² = 0.41) decreased. In the proximal half of the small intestine, no effects of dietary BG level were observed. In the distal half of the small intestine, water-binding capacity (WBC) of digesta increased (0.11 g/g digesta DM per % dietary BG, P = 0.028 and R² = 0.24) and starch digestibility decreased (0.3% per % dietary BG, P = 0.034 and R² = 0.23) when dietary BG level increased. In the colon, apparent digesta viscosity at 45/s shear rate increased (0.1 Pa × s per % dietary BG, P = 0.03 and R² = 0.24) in the proximal half of the colon, and digesta WBC increased (0.06 g/g digesta DM per % dietary BG, P = 0.024 and R² = 0.26) in the distal half of the colon when dietary BG level increased. To conclude, increasing dietary BG level caused the MRT of liquids, but not that of solids, to increase in the stomach, resulting in reduced separation of the solid and liquid digesta fractions. This caused dilution of the stomach content and reduction in digesta viscosity when dietary BG levels increased. Effects of dietary BG level on physicochemical properties in the proximal small intestine were absent and may have been due to a low DM content. The WBC of digesta in the distal small intestine and colon increased when dietary BG level increased, as did apparent digesta viscosity in the proximal colon. This likely reflects the concentration of BG in digesta when moving through the gastrointestinal tract.     

Anaerobic bacteria from the digestive tract of North Atlantic fin whales (Balaenoptera physalus)

Abstract Samples were collected from the forestomach and colon of North Atlantic fin whales ( Balaenoptera physalus ) landed at the commercial whaling station at Hvalfjördur, Iceland during three whaling seasons. Techniques were used to enrich for and enumerate anaerobic bacteria, methanogens, and sulfate reducers. Anaerobic bacteria ranged from 10⁸ to 10¹⁰ per ml of digesta in the colon, and from 10⁵ to 10⁹ per ml of digesta in the forestomach. Methanogens and sulfate-reducing bacteria were found in the majority of forestomach and colon samples, with sulfate-reducing bacteria usually occuring at higher concentrations. Enteric bacteria, Vibrio , and Listonella spp. were found in the colon. Volatile fatty acids were detected in significant concentrations in the forestomach of many of the whales. These results support previous findings which suggest that a microbial fermentation occurs in the forestomach of baleen whales.     

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.     

Absorption and secretion in the tubiform forestomach (compartment 3) of the llama

Summary Extensive absorption occurrs in the tubelike last section of the forestomach of the llama (compartment 3); 70% of the short chain fatty acids, 60% of the sodium, and 30% of the water that entered this compartment of the forestomach was absorbed durint their passage. Secretion of chloride in compartment 3 was in the order of magnitude of the amount of chloride that entered with digesta. Net absorption of sodium and water were closely related.     

Flow rates of components in digesta of pigs prepared with re-entrant cannulas in the proximal duodenum and terminal ileum, and fed semipurified, hard wheat, and soft wheat diets.

Four pigs prepared with re-entrant cannulas in the proximal duodenum and terminal ileum were used to study flow rates of total digesta, insoluble dry matter, nitrogen, and amino acids entering and leaving the small intestine. The pigs received a semipurified diet, a hard wheat diet, or a soft wheat diet. These were approximately isonitrogenous. A higher rate of passage of digesta through the proximal duodenum and terminal ileum were measured in pigs receiving the hard wheat diet. Peak flow of digesta at the duodenum of all pigs occurred at 1 h post feeding. Peak flow of digesta at the ileum occurred at 9 h post feeding on the soft wheat diet, but somewhat earlier on the hard wheat and semipurified diet. More nitrogen and essential amino acids flowed in the solid fraction of duodenal digesta during the first 2 h post feeding for the wheat diets and 4 h post feeding for the semipurified diet. It was concluded that flow rate of most nutrients from the stomach and through the small intestine of pigs is modified by the composition and texture of the food ingested. It is postulated that efficiency of mixing of digesta with digestive secretions in the stomach is a major factor influencing rate of flow.     

Intestinal lactase (beta-galactosidase) and other glycosidase activities in suckling and adult tammar wallabies (Macropus eugenii)

The activities of various glycosidases in homogenates of the small intestinal mucosa of two adult and 18 suckling tammar wallabies (M. eugenii) aged from 6 to 50 weeks were investigated. Lactase (beta-D-galactosidase), beta-N-acetylglucosaminidase, alpha-L-fucosidase and neuraminidase activities were high during the first 34 weeks post partum and then declined to very low levels. Maltase, isomaltase, sucrase and trehalase activities were very low or absent during the first 34 weeks, and then increased. The lactase activity was unusual in being greater in the distal than the middle or proximal thirds of the intestine, and in its low pH optimum (pH 4.6), inhibition by p-chloromercuribenzene sulfonate but not by Tris, and lack of cellobiase activity. These properties are those of a lysosomal acid beta-galactosidase rather than of a brush border neutral lactase. The maltase activity had the characteristics of a lysosomal acid alpha-glucosidase early in lactation and of a brush border neutral maltase in adult animals. The significance of these findings is discussed in relation to changes in dietary carbohydrates during weaning and to the mode of digestion of milk carbohydrates by the pouch young.     

Retention of different-sized particles and derived gut fill estimate in tammar wallabies (Macropus eugenii): physiological and methodological considerations

The capacity of the digestive tract is an important parameter in understanding digestive adaptations, particularly in herbivores. Measures of this capacity (‘gut fill’) are commonly performed in killed animals, which has ethical and logistical implications. Alternatively, dry matter gut contents (DMC) can be estimated in live animals from food intake, digesta retention and digestibility, based on physical principles (Holleman and White, Can. J. Zool. 67, 488-494, 1989). Although this method has been used to some extent, it still awaits thorough validation. Here we estimated DMC in seven tammar wallabies during 5-day feeding trials and compared the results to those gained from dissections immediately after the trials. Calculated DMC exceeded that actually measured by 29 ± 22%. A closer inspection of the data suggested that this was partly due to the fact that DMC as measured by dissection is susceptible to short-term influences such as daily variation in food intake, whereas the calculated DMC represents an integrative measure over the whole period of the feeding trial. Correlations between both the measured digesta retention times, and the calculated DMC, with the measured wet contents mass suggest that it is particularly the DMC determined via dissection that needs to be measured with care. For a comparison of gut capacities, the calculated DMC therefore can be considered adequate, but should for a more widespread use be validated in further studies including more species and experimental regimes controlling food intake variation. Additionally, we tested whether very small (100-500 μm) and small (500-1000 μm) particles were retained differently in the tammar wallabies. There was no indication of such a difference. Whether the macropod forestomach selectively passes a certain particle fraction (that represents microbes) with the generally faster-passing fluids remains to be investigated with even smaller markers, e.g. labelled bacteria.     

the influence of lentinus edodes (shiitake mushroom) preparations on bacteriological and morphological aspects of the small intestine in piglets

Among substances intended to replace growth promoting antibiotics in pig nutrition, non-digestible oligosaccharides or polysaccharides could be potential alternative compounds. Therefore, the influence of β-1,3-1,6 glucans on bacteriological, biochemical and morphological aspects of the small intestine in weaned piglets was investigated. As sources of β-glucans, Lentinan (extract of Lentinus edodes mycelium) or dried L. edodes mycelium were added to the diet. Four homogenous groups of 5 newly weaned piglets (4 weeks of age) received one of four diets: control diet (C), C supplemented with Avilamycin (50?mg/kg, positive control), C supplemented with 0.1% of Lentinan and C supplemented with 5% of dried L. edodes mycelium powder. A first group of 10 piglets was euthanized after 11 days and the remaining 10 on day 12 of the experiment. The gastrointestinal tract was divided in segments and samples taken from digesta (stomach, proximal and distal jejunum, caecum), mucosal scrapings (jejunum) and ring shaped tissue samples (1?cm) of proximal and distal jejunum. Bacterial counts were made with digesta and mucosal samples, and short-chain fatty acids (SCFA), lactic acid and ammonia concentrations were determined. Tissue samples of both jejunal sites were embedded in paraffin wax for morphometrical (villus length, crypt depth) and histological observations (numbers of intraepithelial lymphocytes (IEL), goblet cells, apoptotic enterocytes on villi, mitotic cells in crypts). Only the diet containing 5% of dried L. edodes consistently resulted in lower viable counts (ca. 1?–?2 log₁₀ CFU) of total bacteria, E. coli, streptococci and lactic acid bacteria, and luminal and mucosal effects agreed very well. With this diet, acetate and butyrate concentrations in the distal jejunum were doubled, which is favourable in view of the trophic effect on enterocytes and colonocytes. Villus length (V) was increased with both diets containing β-glucans while crypt depth (C) was not altered, but V/C was higher. IEL counts were decreased by both diets although bacterial numbers, which is only one parameter of bacterial load, were only diminished with the L. edodes feed. The three supplemented feeds lowered the number of apoptotic enterocytes on the villi, but these numbers were very low (control diet?:?44 cells per 100 villi), making clear interpretation difficult. The mitotic index was slightly lower with the L. edodes feed, although not statistically significant. Decreased viable counts observed with the latter diet is a favourable effect as it is accepted that a lower bacterial load causes lower turnover rates of the intestinal epithelial cells, while there is also less competition for specific substrates. A higher V/C ratio, a smaller number of IEL in the epithelium and a lower apoptotic index also indicate slower turnover rate of the mucosa when Lentinan and L. edodes diets were fed. The inconsistent effects observed with Lentinan were probably due to the low amount added to the diet. It should be taken into account that the influence of L. edodes mycelium powder was more likely due to the presence of antibacterial compounds (eg. lenthionine, lentinamycin, terpenoids, polyphenols), rather than to an immunostimulating action of β-glucans with increased release of IgA onto the mucosa surface.     

Incorporation of galactomannans in the diet of newly weaned piglets: effect on bacteriological and some morphological characteristics of the small intestine

In search of substances replacing antibiotics as growth promoters for farm animals, non-digestible oligosaccharides (NDO) or non-starch polysaccharides (NSP) have been proposed as possible alternatives. In this context, the influence of galactomannans on bacteriological and morphological aspects of the gastrointestinal tract in weanling pigs was investigated. Four groups of five newly weaned piglets received one of the following diets: control feed (C), C supplemented with guar gum (1%), C supplemented with locust bean gum (1%) and C supplemented with 10% of carob tree seeds meal as source of locust bean gum. The animals were euthanized after 11-12 days and digesta were sampled in stomach, jejunum (proximal and distal) and caecum, while mucosal scrapings and ring shaped tissue samples were taken of proximal and distal jejunum. On these samples bacteriological, biochemical and morphological determinations were carried out. Total count of bacteria in digesta and mucosal scrapings was not influenced by the different diets, with the exception of the proximal jejunum where a small decrease (0.5 log10 CFU) was noted with the guar gum and carob tree seeds diet. The number of E. coli increased by feeding both gums and carob tree seeds. With the latter diet, higher counts of streptococci were observed. In agreement with the lower concentration of lactic acid in jejunal contents, guar gum decreased the number of lactobacilli. Locust bean gum decreased the molar proportion of acetate in caecal contents while butyrate and valerate were augmented. Feeding the carob tree seeds resulted in shorter villi and a lower villus height/crypt depth ratio in the jejunum mucosa, which was an indication for a faster renewal rate of the epithelium. Both locust bean gum feeds significantly lowered the mitotic index in the crypts of the small intestine. Only with the carob tree seeds diet, viscosity of jejunal contents was increased. In conclusion, the effects of the addition of 1% of pure guar gum or locust bean gum were inconsistent and not very outspoken, whereas 10% of carob tree seeds meal in the diet resulted in influences on intestinal characteristics at the bacteriological and morphological level.     

Digesta passage rates in the Florida manatee (Trichechus manatus latirostris)

The Florida manatee, Trichechus manatus latirostris (Sirenia: Trichechidae), is an herbivorous marine mammal found within coastal areas throughout the state of Florida, which feeds on both fresh and salt water sea grasses. Manatees, like other Sirenians, are a tropical species with little tolerance for water temperatures below 20°C, rely on a relatively poor nutritional food source, and have a low metabolic rate. Although manatees are hindgut fermenting herbivores, they are very efficient at extracting nutrients from the plants on which they feed. Slow passage rates of digesta have been suggested to be a factor in this increased efficiency. Two studies monitored the digesta passage times and mixing of particulate digesta within the manatee digestive tract using MicroGrits colored corncob grit as a fecal marker. Fecal samples were collected subsequently from four manatees in Study 1 and 3 manatees in Study 2, grit pieces removed, counted, and measured. The digesta passage times ranged from 6 and 10 days in Study 1, and 4.3 and 8.3 days in Study 2, supporting data presented in previous studies. When two different colored markers were administered on sequential days, minimal to no mixing was seen in recovered feces, suggesting that the digesta from a given day traveled through the tract as a bolus. Less than 1% of the marker fed was recovered and we hypothesize that perpendicular folds of the large intestine may be the major contributing factor, with pieces being retained and eventually digested. Zoo Biol 26:503–515, 2007. © 2007 Wiley‐Liss, Inc.     

Comparative red blood cell metabolism in three wallaby species, Macropus eugenii, Macropus parma and Thylogale thetis (Macropodidae: Marsupialia)

Aspects of red blood cell metabolism were compared among three species of small macropodid marsupials from different habitats. Packed cell volume (PCV), erythrocyte reduced glutathione (GSH) concentration and GSH regeneration rates were similar in all three species. The Parma wallaby had very low red cell potassium levels compared to the other species studied. The Tammar wallaby had higher rates of glucose consumption and lactate production in vitro at both pH 7.4 and 8.2 than did the Parma and significantly lower adenosine triphosphate (ATP) levels than the other species. These findings are consistent with preliminary reports published previously. The differences noted cannot be directly related to differences in the habitats of the species.     

Function,size and form of the gastrointestinal tract of the collared <Emphasis Type="Italic">Pecari tajacu</Emphasis> (Linnaeus 1758) and white-lipped peccary <Emphasis Type="Italic">Tayassu pecari</Emphasis> (Link 1795)

The peccary digestive tract is characterised by an elaborate forestomach. In order to further characterise the digestive function of peccaries, we report body mass, digestive organ mass, content mass of the gastrointestinal tract compartments and their length and width, as well as liver, parotis and mandibular gland mass. Our data on eleven collared and four white-lipped peccaries suggest that peccaries have a small relative stomach volume compared to other foregut fermenters, which implies a comparatively lower fermentative capacity and thus forage digestibility. The forestomach could enable peccaries to deal, in conjunction with their large parotis glands, with certain plant toxins (e.g. oxalic acid). The finding of sand being trapped in the forestomach blindsacs could indicate a disadvantage of the peccary forestomach design. The relevance of the forestomach to peccaries remains enigmatic.     

Physical characteristics of digesta and their influence on flow and mixing in the mammalian intestine: a review

The physical properties of digesta may influence mixing, efficiency of digestion, and absorption within the lumen of the intestine. We review how the physical properties of digesta change during transit through the various segments of the intestine, and how their influence on flow and mixing may be modulated by peristaltic activity. We examine how, in more fluid digesta, the solid and liquid phases interact to influence flow and mixing. Similarly, how in viscid digesta, shear strength, plasticity and elasticity of contained particulate material may influence the permeation of the fluid phase and secretions into and out of the digesta bolus. The manner in which the solid and liquid phases of digesta interact in a partly gaseous environment, such as the lower bowel, to influence bolus cohesion is also examined. Those mechanisms that promote the formation of a less viscous layer at the mucosal interface to promote plug flow are reviewed, and their effect on the efficiency of mixing and digestion discussed. It is recommended that in any future work investigating the character of mixing in the intestine, a wider range of appropriate digesta properties be measured and that, in investigations of intestinal movement, perfusates with similar characteristics to digesta be used.     

Reticulo-ruminal motility in cattle (Bos indicus) and water buffaloes (Bubalus bubalis) fed a low quality roughage diet

1. The effect of A and B sequence contractions of the reticulo-rumen on passage rate of digesta was compared in buffaloes and cattle fed low quality rhodes grass. 2. Both species ate the same amount per unit body weight but buffaloes spent 53% more time ruminating than cattle. 3. Buffaloes had fewer A and B sequence contractions each day and the rate of these contractions during eating, ruminating and at rest were slower. 4. A larger pool of fine feed particles in the rumen of buffaloes, generated by extra ruminating activity was associated with the 30% shorter mean residence time of particulate matter in the forestomach compared with cattle. 5. It is concluded that the difference in the number and frequency of contractions between the species was insufficient to affect passage rate of digesta from the stomach.     

Incorporation of galactomannans in the diet of newly weaned piglets: Effect on bacteriological and some morphological characteristics of the small intestine

In search of substances replacing antibiotics as growth promoters for farm animals, non-digestible oligosaccharides (NDO) or non-starch polysaccharides (NSP) have been proposed as possible alternatives. In this context, the influence of galactomannans on bacteriological and morphological aspects of the gastrointestinal tract in weanling pigs was investigated. Four groups of five newly weaned piglets received one of the following diets: control feed (C), C supplemented with guar gum (1%), C supplemented with locust bean gum (1%) and C supplemented with 10% of carob tree seeds meal as source of locust bean gum. The animals were euthanized after 11?–?12 days and digesta were sampled in stomach, jejunum (proximal and distal) and caecum, while mucosal scrapings and ring shaped tissue samples were taken of proximal and distal jejunum. On these samples bacteriological, biochemical and morphological determinations were carried out. Total count of bacteria in digesta and mucosal scrapings was not influenced by the different diets, with the exception of the proximal jejunum where a small decrease (0.5 log₁₀ CFU) was noted with the guar gum and carob tree seeds diet. The number of E. coli increased by feeding both gums and carob tree seeds. With the latter diet, higher counts of streptococci were observed. In agreement with the lower concentration of lactic acid in jejunal contents, guar gum decreased the number of lactobacilli. Locust bean gum decreased the molar proportion of acetate in caecal contents while butyrate and valerate were augmented. Feeding the carob tree seeds resulted in shorter villi and a lower villus height/crypt depth ratio in the jejunum mucosa, which was an indication for a faster renewal rate of the epithelium. Both locust bean gum feeds significantly lowered the mitotic index in the crypts of the small intestine. Only with the carob tree seeds diet, viscosity of jejunal contents was increased. In conclusion, the effects of the addition of 1% of pure guar gum or locust bean gum were inconsistent and not very outspoken, whereas 10% of carob tree seeds meal in the diet resulted in influences on intestinal characteristics at the bacteriological and morphological level.     

Differential passage of fluids and different-sized particles in fistulated oxen (Bos primigenius f. taurus), muskoxen (Ovibos moschatus), reindeer (Rangifer tarandus) and moose (Alces alces): Rumen particle size discrimination is independent from contents stratification

Ruminant species differ in the degree that their rumen contents are stratified but are similar insofar that only very fine particles are passed from the forestomach to the lower digestive tract. We investigated the passage kinetics of fluid and particle markers (2, 10 and 20 mm) in fistulated cattle (Bos primigenius f. taurus), muskoxen (Ovibos moschatus), reindeer (Rangifer tarandus) and moose (Alces alces) on different diets. The distribution of dry matter in the rumen and the viscosity of rumen fluids suggested that the rumen contents were more stratified in muskoxen than moose. Correspondingly, as in previous studies, the species differed in the ratio of mean retention times of small particles to fluids in the reticulorumen, which was highest in cattle (2.03) and muskoxen (1.97–1.98), intermediate in reindeer (1.70) and lowest in moose (0.98–1.29). However, the ratio of large to small particle retention did not differ between the species, indicating similarity in the efficiency of the particle sorting mechanism. Passage kinetics of the two largest particle classes did not differ, indicating that particle retention is not a continuous function of particle size but rather threshold-dependent. Overall, the results suggest that fluid flow through the forestomach differs between ruminant species. A lower relative fluid passage, such as in moose, might limit species to a browse-based dietary niche, whereas a higher relative fluid passage broadens the dietary niche options and facilitates the inclusion of, or specialization on, grass. The function of fluid flow in the ruminant forestomach should be further investigated.     

Differential Expression of Nonagglutinating Fimbriae and MR/P Pili in Swarming Colonies of Proteus mirabilis

The expression of nonagglutinating fimbriae (NAF) and mannose-resistant/Proteus-like (MR/P) pili in swarming colonies of Proteus mirabilis was investigated. Elongated swarmer cells do not express pili, and the relative number of bacteria expressing NAF during swarming and early consolidation phases was very low (<5%). Relative expression of NAF in a terrace increased to approximately 30% at 48 h. We also determined the expression of NAF and MR/P pili in two phenotypically distinguishable regions of each terrace. The expression of both NAF and MR/P pili was always higher in the region closer (proximal) to the middle of the colony than in the distal region of the terrace. The relative numbers of bacteria expressing NAF or MR/P pili in the proximal region were between 39.1 and 63% and between 5.9 and 7.7%, respectively. In the distal region, expression levels were between 20.8 and 27.3% and between 3.7 and 5. 6%, respectively. A time course experiment testing NAF expression in both the proximal and distal regions of a terrace indicated that NAF expression in the proximal regions was always higher than in the distal regions and increased to a plateau 40 to 50 h after the start of the swarming phase for any given terrace. These results indicate that expression of NAF or MR/P pili in swarming colonies of P. mirabilis is highly organized, spatially and temporally. The significance of this controlled differentiation remains to be uncovered.     

The passage of digesta, particle size, and in vitro fermentation rate in the three-toed sloth Bradypus tridactylus (Edentata: Bradypodidae)

The digestive physiology of six three-toed sloths ( Bradypus tridactylus ) fed exclusively on Cecropia palmata foliage was studied. The mass of digesta in the gut was between 17 and 37% of body mass. This was between 133 and 282% of that expected in an animal of this size, based on published allometric equations. The concentration of total short chain fatty acids in the stomach was similar to that in the fermentative regions of other foregut fermenting herbivores but the rate of fermentation measured in vitro was very slow (6–12 mmol.l^-1.h^-1) and substantially lower than that observed using similar techniques in other small foregut fermenters.
The overall (dose to excretion) mean retention time of particulate and solute digesta markers was about 150 h. Most of this (73%) occurred in the stomach but a substantial proportion (17%) could be attributed to the storage of faeces in the rectum.
The slow rate of passage of digesta through the gut together with the slow rate of fermentation in the stomach is not typical of small foregut fermenting herbivores. However, such a pattern is feasible in Bradypus tridactylus because of the large volume of digesta retained in the gut and the very low metabolic rate of these mammals.