Dimensions of the intestine, diet and faecal water loss in some African antelope

Measurements of the intestine of 16 species of antelope were allometrically analysed. Moisture content of the digesta showed greatest interspecific variation in the spiral and distal colon. Small intestine length showed positive allometry, its circumference showed negative allometry, resulting in a surface area which was isometric or related to metabolic rate. Dimensions of the villi were non-allometric. Grazers had lower surface areas of the small intestine than intermediates/concentrate selectors owing to smaller circumferences. In the large intestine, the dimensions of the distal colon showed the greatest interspecific variation. Lengths of the large intestine showed positive allometry except for the caecum which was isometric. Circumferences and areas of the large intestine were isometric or related to metabolic rate. Species producing dry dung had larger lengths and areas of the large intestine but a smaller circumference of the proximal and spiral colon and also showed greater drying of digesta per unit area than those producing wetter dung. Grazers had smaller lengths, circumferences and areas of the large intestine than intermediates/concentrate selectors.     

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.     

Participation of the adrenergic receptors in the regulation of large bowel motor activity in sheep

In sheep with long-standing fistulae of the caecum, proximal loop of the colon and rumen the motor activity of these parts of the intestine was studied using the balloon method. Slow isoprenaline infusion caused first inhibition of caecal contractions, followed by gradually decreasing intensity of contractions of the colon and rumen. This inhibitory effect of isoprenaline was eliminated by propranolol. Intravenous infusion of phenylephrine failed to inhibit the colonic motor activity. A small dose of atropine, similarly as isoprenaline, caused an irregular inhibition of the contractions of the caecum, colon and rumen. In sheep, in contrast to other animal species, the effects inhibiting large intestine motility are mediated only by the beta-adrenergic receptors. The inhibitory effect of the beta-adrenergic receptors was strongest in the caecum.     

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.     

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.     

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.     

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.     

Selective digesta retention and coprophagy in Brandt's vole (Microtus brandti)

Digestive performance, gut morphology and rate of digesta passage were measured in Brandt's voles (Microtus brandti) offered pelleted diets of low (25% neutral-detergent fibre) and high (38%) fibre content. Digestion coefficients of dry matter, crude fat, crude protein, energy and fibre were all significantly lower on the higher fibre diet. Although not significantly higher, dry matter intakes were more than maintained when extra cellulose was included in the diet, so that intakes of digestible energy were only 22% lower on the higher fibre diet. Total length and total gut tissue weight increased significantly, and the length and tissue weight of the caecum, proximal colon, and distal colon were significantly greater on the higher fibre diet as well. Total tract mean retention time (MRT) of a solute marker (Co-EDTA) was significantly greater than that of a particle marker (Cr-cell walls) on the lower fibre diet, and in the same direction on the higher fibre diet. The ratio of solute to particle MRTs (the solute/particle differential retention ratio) was 1.45 on the lower fibre diet and 1.19 on the higher fibre diet. There were no significant differences in marker MRTs between diets. Examination of marker concentrations in the stomach, small intestine, caecum and colon of voles killed at 0.5-h intervals after a pulse dose of Co-EDTA indicated that the marker was recycled to the stomach by coprophagy. Thus, as in other microtine rodents, an increase in gut capacity, selective digesta retention and recycling of digesta via coprophagy enables Brandt's voles to utilise diets of higher fibre content than may be expected for such a small (45 g) mammalian herbivore.     

The gastrointestinal tract of the rock hyrax (Procavia habessinica). 1. Morphology and motility patterns of the tract

The stomach of the rock hyrax (Procavia habessinica) is divided into a non glandular part with very slow movements, and a glandular part which rapidly mix the digesta. The large intestine has two fermentation chambers, the caecum, which rapidly mixes the digesta, and the colonie sac, which efficiently, but slowly, mixes digesta. Between these chambers runs the connecting colon. No retrograde transport is observed in any part of the large intestine.     

Digestive performance and selective digesta retention in the long-nosed bandicoot,Perameles nasuta,a small omnivorous marsupial

Bandicoots are opportunistic omnivores that feed on invertebrates, fungi and both epigeal and hypogeal plant parts. We examined the performance of the digestive tract of the long-nosed bandicoot (Perameles nasuta) in terms of intake and total digestibility, patterns of excretion of inert digesta markers, and likely sites of digesta retention, on two diets designed to mimic part of their natural plant and insect diets. On the insect diet (mealworm larvae), bandicoots virtually maintained body mass at a digestible energy intake of 511 kJ · kg^-0.75 · day^-1 and were in strongly positive nitrogen balance. In contrast, on the plant diet (shredded sweet potato), bandicoots ate only one-third as much digestible energy, lost 7% body mass, and were in negative nitrogen balance. Mean retention times of two particle markers on the plant diet (27.5 and 27.0 h) were more than double those on the insect diet (12.4 and 11.2 h), and on both diets the mean retention time of the fluid digesta marker was greater than those of the particle markers, indicating consistent selective retention of fluid digesta in the gut. It was seen radiographically than in mealwormfed bandicoots major sites of digesta retention were the distal colon and rectum, whereas in the sweet potato-fed animals the caecum and proximal colon were principal sites. It was concluded that retention of plant material in the caecum and proximal colon (the main sites of microbial digestion) and the preferential retention of fluid digesta (together with bacteria and small feed particles) in the caecum were important factors in the ability of bandicoots to switch between insect and plant foods, depending on relative availabilities, and thus to exploit nutritionally unpredictable environments.Abbreviations ADF acid-detergent fibre - bm body mass - Co-ED-TA cobalt-ethylenediaminetetra-acetic acid - CWC cell wall constituents - DE digestable energy - dm dry matter - EUN endogenous urinary nitrogen - ICP inductively-coupled plasma atomic emission spectroscopy - MFN metabolic faecal nitrogen - MRT mean retention time - NDF neutral-detergent fibre - ww wet weight     

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.     

The effects of inulin,dried Jerusalem artichoke tuber and a multispecies probiotic preparation on microbiota ecology and immune status of the large intestine in young pigs

The study aimed at determining the effect of two types of prebiotics and a multispecies probiotic on microbiota activity and composition, as well as mucosal immunity in the large intestine of young pigs. In total 48 piglets were divided into 6 groups (n = 8), which received from day 10 of life probiotic-unsupplemented (PU) or probiotic-supplemented (PS) diets. Probiotics were added at 0.5 g/kg diet and contained: Lactococcus lactis, Carnobacterium divergens, Lactobacillus casei, Lactobacillus plantarum and Saccharomyces cerevisiae. The PU and PS diets were formulated without prebiotic addition (control) or with addition of 2% of inulin from chicory root (IN) or 4% of dried Jerusalem artichoke tubers (DJA). After 40 days of feeding, digesta and tissue samples were taken from the caecum and three sections of the colon for analyses of microbiota activity and composition, secretory immunoglobulin A (sIgA) and intraepithelial lymphocytes (IEL). IN diets decreased the caecal digesta pH and β-glucosidase activity but increased propionic, valeric and total short chain fatty acid (SCFA) concentrations compared to control diets. Feeding DJA diets increased caecal valeric acid level, decreased the concentration of isoacids in the colon, reduced β-glucosidase and β-glucuronidase activity in the middle colon and increased Bifidobacterium spp. populations in the proximal and distal colon. PS diets increased the caecal acetic acid and total SCFA level, and Clostridium spp. populations in the distal colon. Neither probiotic nor prebiotics affected sIgA level or IEL number in the large intestine. In conclusion, DJA modified the microbiota ecology in the large intestine of young pigs to a greater extent than IN and the applied probiotic did not enhance effects of prebiotics.     

Distribution of enteric nerve cells that project to the coeliac ganglion of the guinea-pig

Summary The digestive tract of the guinea-pig, from the esophagus to the rectum, was examined in detail to determine the distribution and relative abundances of neurons in these organs that project to the coeliac ganglion and the routes by which their axons reach the ganglion. A retrogradely transported neuronal marker, Fast Blue, was injected into the coeliac ganglion. The esophagus, stomach, gallbladder, pancreas, duodenum, small intestine, caecum, proximal colon, distal colon and rectum were analysed for labelled neurons. Retrogradely labelled neurons were found only in the myenteric plexus of these organs, and in the pancreas. No labelled neurons were found in the gallbladder or the fundus of the stomach, or in the submucous plexus of any region. A small number of labelled neurons was found in the gastric antrum. An increasing density of labelled neurons was found along the duodenum. Similarly, an increasing density of labelled neurons was found from proximal to distal along the jejuno-ileum. However, the greates densities of labelled neurons were in the large intestine. many labelled neurons were found in the caecum, including a high density underneath its taeniae. An increasing density of labelled neurons was found along the length of the proximal colon, and labelled neurons were found in the distal colon and rectum. In total, more labelled cell bodies occurred in the large intestine than in the small intestine. The routes taken by the axons of viscerofugal neurons were ascertained by lesioning the nerve bundles which accompany vessels supplying regions of the digestive tract. Viscerofugal neurons of the caecum project to the coeliac ganglion via the ileocaeco-colic nerves; neurons in the proximal colon project to the ganglion via the right colic nerves, and neurons in the distal colon project to the ganglion via the mid colic and intermesenteric nerves. Neurons in the rectum project to the coeliac ganglion via the intermesenteric nerves. These nerves (except for the intermesenterics) all join nerve bundles from the small intestine that follow the superior mesenteric artery. All viscerofugal neurons of the caecum were calbindin-immunoreactive (calb-IR) and 94% were immunoreactive for vasoactive intestinal peptide (VIP-IR). In the proximal colon, 49% of labelled neurons were calb-IR and 85% were VIP-IR. In the distal colon, 80% of labelled neurons were calb-IR and 71% were VIP-IR.     

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.     

Evidence of a rudimentary colon in the elasmobranch, Leucoraja erinacea

The transition from aquatic to terrestrial life presented tetrapodamorphs with the challenge of maintaining water homeostasis and preventing desiccation on land. The colon evolved in terrestrial vertebrates to help maintain fluid balance. Although marine elasmobranchs lack a colon, their spiral intestine contains a subregion that histologically appears to be colon-like, possibly representing an evolutionary precursor to terrestrial digestive tracts. The distal-most region of the spiral intestine of elasmobranchs has no villi and a large number of acid mucins: hallmarks of water absorption in the colons of terrestrial animals. To determine if histologically distinct regions of the elasmobranch digestive tract correspond to functional differences, we compared water absorption in different subregions of the skate, Leucoraja erinacea digestive tract. Water absorption in stomach and spiral intestinal sacs was linear with time and not hydrostatic pressure-dependent. The histologically distinct distal portion of the spiral intestine had a threefold higher rate of water absorption than the proximal portion of the spiral intestine. In addition, the water-selective, colon-specific aquaporin 4 is expressed strongly in the distal spiral intestine epithelia, correlating with the region of the spiral intestine exhibiting the greatest rate of water absorption. We demonstrate that the distal spiral intestine is histologically and functionally distinct from the rest of the spiral intestine and represents a rudimentary colon within the vertebrate lineage.     

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.     

Ecophysiology and nutritional niche of the bilby (Macrotis lagotis), an omnivorous marsupial from inland Australia: a review

The bilby (Macrotis lagotis) is a small omnivorous marsupial that was once widespread but is now restricted to the most arid margins of its former range. It feeds on a mixture of invertebrates (mainly ants and termites) and plant material (mainly seeds and bulbs), most of which is below ground. Measurements of the energy and water requirements of free-living bilbies and of the maintenance nitrogen requirements of captive animals provided the basis for an explanation for its continued survival in the Australian arid zone. Measurements of the mean retention times of inert markers for the solute and particulate phases of digesta revealed no selective retention of solutes and small particles in the caecum. Lack of selective digesta retention in the bilby hindgut helps to explain why the plant component of their diet consists predominantly of seeds and bulbs of relatively low fibre content. This is in contrast to the stems and leaves eaten by other bandicoots, all of which appear to have a colonic separation mechanism that not only selectively retains small particles in the caecum but also facilitates the passage of large fibrous particles through the colon. The ability of the bilby to survive in the Australian arid zone is related to low water and nitrogen requirements and the abundance of ants, termites, bulbs and seeds. Foraging efficiency is maximised by exploiting the underground nests of seed-harvesting ants.     

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.     

Colonization of cattle intestines by Campylobacter jejuni and Campylobacter lanienae

The location and abundance of Campylobacter jejuni and Campylobacter lanienae in the intestines of beef cattle were investigated using real-time quantitative PCR in two studies. In an initial study, digesta and tissue samples were obtained along the digestive tract of two beef steers known to shed C. jejuni and C. lanienae (steers A and B). At the time of slaughter, steer B weighed 540 kg, compared to 600 kg for steer A, yet the intestine of steer B (40.5 m) was 36% longer than the intestine of steer A (26.1 m). In total, 323 digesta samples (20-cm intervals) and 998 tissue samples (3.3- to 6.7-cm intervals) were processed. Campylobacter DNA was detected in the digesta and in association with tissues throughout the small and large intestines of both animals. Although C. jejuni and C. lanienae DNA were detected in both animals, only steer A contained substantial quantities of C. jejuni DNA. In both digesta and tissues of steer A, C. jejuni was present in the duodenum and jejunum. Considerable quantities of C. jejuni DNA also were observed in the digesta obtained from the cecum and ascending colon, but minimal DNA was associated with tissues of these regions. In contrast, steer B contained substantial quantities of C. lanienae DNA, and DNA of this bacterium was limited to the large intestine (i.e., the cecum, proximal ascending colon, descending colon, and rectum); the majority of tissue-associated C. lanienae DNA was present in the cecum, descending colon, and rectum. In a second study, the location and abundance of C. jejuni and C. lanienae DNA were confirmed in the intestines of 20 arbitrarily selected beef cattle. DNA of C. jejuni and C. lanienae were detected in the digesta of 57% and 95% of the animals, respectively. C. jejuni associated with intestinal tissues was most abundant in the duodenum, ileum, and rectum. However, one animal contributed disproportionately to the abundance of C. jejuni DNA in the ileum and rectum. C. lanienae was most abundant in the large intestine, and the highest density of DNA of this bacterium was found in the cecum. Therefore, C. jejuni colonized the proximal small intestine of asymptomatic beef cattle, whereas C. lanienae primarily resided in the cecum, descending colon, and rectum. This information could be instrumental in developing efficacious strategies to manage the release of these bacteria from the gastrointestinal tracts of cattle.     

The allometry of rodent intestines

This study examined the allometry of the small intestine, caecum, colon and large intestine of rodents (n = 51) using a phylogenetically informed approach. Strong phylogenetic signal was detected in the data for the caecum, colon and large intestine, but not for the small intestine. Most of the phylogenetic signal could be attributed to clade effects associated with herbivorous versus omnivorous rodents. The herbivorous rodents have longer caecums, colons and large intestines, but their small intestines, with the exception of the desert otomyine rodents, are no different to those of omnivorous rodents. Desert otomyine rodents have significantly shorter small intestines than all other rodents, reflecting a possible habitat effect and providing a partial explanation for the low basal metabolic rates of small desert mammals. However, the desert otomyines do not have shorter colons or large intestines, challenging claims for adaptation to water retention in arid environments. Data for the Arvicolidae revealed significantly larger caecums and colons, and hence longer large intestines, with no compensatory reduction in the length of the small intestine, which may explain how the smallest mammalian herbivores manage to meet the demands of a very high mass-specific metabolic rate. This study provides phylogenetically corrected allometries suitable for future prediction testing.