Caecal Bacteria Research Articles

Limitations of Owl Reproduction in the Wild: is there a Role for Food Quality Besides Quantity?

Avian studies have shown that food quality (amino acid load) can act as a limiting factor in reproduction and possibly breeding density. In owls, the role of food quality may have been largely overlooked due to the strong effect of food quantity. I examined evidence of food quality limitation in owl reproduction from four sets of data: (1) population data in Tawny Owls and diurnal birds of prey in a degenerate forest, (2) post-laying breast muscle conditions of Tawny Owls Strix aluco and Sparrowhawks Accipiter nisus which strongly relied on internal amino acid stores during egg formation, (3) amino acid deficiency-related embryo anomaly data in failed eggs of Barn Owls Tyto alba, Little Owls Athene noctua, and two reference species, and (4) growth of Tawny Owl chicks experimentally fed with day-old chickens or mice. The Tawny Owl population was found to be stable whereas sympatric bird of prey species greatly declined; breeding female Tawny Owls (n = 5) did not show a decline of breast muscle tissue as was found in Sparrowhawks. Embryo mortality from amino acid deficiency was estimated at 63% and 12% in Barn Owls and Little Owls, respectively. Growth rate of Tawny Owl chicks did not relate to food type. I conclude that egg amino acid investments can affect embryo viability in owls, but mainly in relation to reproductive strategy instead of environment. I hypothesize that owls can obtain additional amino acids from their caecal bacteria, which are lacking in birds of prey, and thereby are less dependent on amino acid availability in the food chain to acquire the amino acids needed for egg formation and chick growth.

Current theories on the pathophysiology of equine laminitis – the link between the gut and foot

Equine laminitis is a painful debilitating condition that seems to be a product of domestication of horses associated with the practice of feeding carbohydrate rich pasture in excess of requirements, particularly in ponies. We have been working on the hypothesis that caecal bacteria, when presented with carbohydrate in large quantities tend to ferment this. Fermentation by gram positive bacteria is associated with a fall in pH of the caecal liquor. As a means of providing themselves with increased intracellular buffering capacity, these bacteria produce amino acid decarboxylase enzymes which convert amino acids present in the caecal fluid into primary amines which can act as intracellular buffers. The reason we thought this might be the case was that foods formed by bacterial fermentation processes (e.g. cheese and wines) have a high content of amines. Primary amines derived from some amino acids have vasoactive properties. In the 1960s it was recognised that human patients taking drugs that inhibit the metabolism of amines (monoamine oxidase inhibitors) could suffer from severe hypertensive crises if they ate cheese or drank red wines with high tyramine content. This so called ‘cheese effect’ is the result of the indirect sympathomimetic effect of tyramine which displaces norepinephrine from sympathetic nerve endings leading to a rise in blood pressure. Monoamine oxidase enzymes present in the epithelial cells lining the gut wall and in liver cells normally protect individuals from suffering these hypertensive crises. We wondered whether amines released from the gut in response to ingestion of excessive amounts of carbohydrate might lead to a similar reaction in ponies whereby dietary amines caused vasoconstriction of the digital vasculature, leading to the prodromal phases of laminitis.

Contribution of gut microbial lysine to liver and milk amino acids in lactating does

The contribution of microbial amino acids through caecotrophy to tissue protein metabolism was investigated in lactating does. Attempts were made to vary microbial supply through a dietary antibiotic, Zn bacitracin, and to vary tissue demand through manipulation of litter size. Three groups of eight New Zealand does were fed different experimental diets from day 28 of pregnancy to day 26 of lactation. The control group received the basal diet formulated to meet requirements with grass hay, wheat, soybean meal and barley grain. The second (no antibiotic) group and the third (bacitracin; BAC) group ingested the basal diet supplemented with ammonium sulfate (5 g/kg), initially unlabelled (day 1 to day 8) then labelled with 15N (day 9 to day 30), while the BAC diet was also supplemented throughout with antibiotic (Zn bacitracin; 100 mg/kg). From just after birth each group of does was subdivided into two groups, each of four females, with the litter size either five (LS5) or nine (LS9) pups. The 15N enrichment in liver, milk and caecal bacteria amino acids was determined by GC-combustion-isotope ratio MS. All amino acids in bacterial protein were enriched with the (15 NH 4)2SO4 treatment, with lysine 15N enrichment significantly greater in caecal bacteria (0.23 (SE 0.0063) atom % excess (ape)) than in liver (0.04 (SE 0.0004) ape) or milk protein (0.05 (SE 0.0018) ape), confirming the double origin (bacterial and dietary) of tissue lysine. The contribution of microbes to tissue lysine was 0.23 (SE 0.006) when milk protein was used as reference.

Potential core species and satellite species in the bacterial community within the rabbit caecum.

A bacteria library was constructed from the caecum of a rabbit maintained under standard conditions. The complete gene 16S rRNA gene was sequenced. The 228 clones obtained were distributed in 70 operational taxonomic units (OTUs). The large majority of the OTUs were composed of one or two clones and seven OTUs contained half of the sequences. Fourteen sequences had high similarity to the sequence already registered in databases (threshold of 97%). Only one of these sequences has been identified as Variovorax sp. (99% identity). Units were distributed mainly (94%) in the Firmicutes phylum. Three sequences were related to Bacteroidetes. Nine clusters were defined in the phylogenic tree. A great diversity of caecal bacteria of the rabbit was shown. Half of the sequences generated in this library were distributed in the phylogenetic tree near the sequences characterized previously in rabbit caecum (potential core species), and the other half of the sequences were well separated (satellite species).

Indigenous bacteria and bacterial metabolic products in the gastrointestinal tract of broiler chickens

The gastrointestinal tract is a dynamic ecosystem containing a complex microbial community. In this paper, the indigenous intestinal bacteria and the microbial fermentation profile particularly short chain fatty acids (SCFA), lactate, and ammonia concentrations are reviewed. The intestinal bacterial composition changes with age. The bacterial density of the small intestine increases with age and comprises of lactobacilli, streptococci, enterobacteria, fusobacteria and eubacteria. Strict anaerobes (anaerobic gram-positive cocci, Eubacterium spp., Clostridium spp., Lactobacillus spp., Fusobacterium spp. and Bacteroides) are predominating caecal bacteria in young broilers. Data from culture-based studies showed that bifidobacteria could not be isolated from young birds, but were recovered from four-week-old broilers. Caecal lactobacilli accounted for 1.5 – 24% of the caecal bacteria. Gene sequencing of caecal DNA extracts showed that the majority of bacteria belonged to Clostridiaceae. Intestinal bacterial community is influenced by the dietary ingredients, nutrient levels and physical structure of feed. SCFA and other metabolic products are affected by diet formulation and age. Additional studies are required to know the bacterial metabolic activities together with the community analysis of the intestinal bacteria. Feed composition and processing have great potential to influence the activities of intestinal bacteria towards a desired direction in order to support animal health, well-being and microbial safety of broiler meat.

Ultradian rhythms and the nutritional importance of caecotrophy in captive Brandt’s voles (Lasiopodomys brandtii)

Ingestion of soft faeces derived from caecal contents, caecotrophy, in herbivorous small mammals is considered an adaptation to the metabolic disadvantage of small body size, especially when feeding on diets of low quality. We investigated daily activity patterns in captive Brandt's voles (Lasiopodomys brandtii), including feeding, locomotion, caecotrophy, and defaecation, by continuous 24 h visual observation; and estimated the contribution of soft faeces ingestion (caecotrophy) to intake of protein and energy. Brandt's voles ingested 68.8 +/- 7.4 fecal pellets per day, averaging 17 +/- 2% of total faeces produced. The amount of faeces ingested did not differ between female and male voles or between night and day time. All animals showed average 3 h ultradian cycles in behaviour during the course of the day and night. The contributions of caecotrophy to the dietary intake of crude protein and metabolizable energy were estimated respectively as 9 and 8% on a high-protein, easily digested commercial rabbit pellet diet. However, the importance of caecotrophy to the field voles is likely to be higher on a natural diet of lower nutrient density. The rhythm of caecotrophy in voles depended mainly on the rhythm of the colonic separation mechanism in the proximal colon and passage in the distal colon, and may be regulated by feeding and other activity rhythms. Ultradian rhythms in caecotrophy helped to minimise potential conflicts in utilizing the gut, especially in balancing the caecal fermentation and salvaging nutrients contained in caecal bacteria.

High fat intake by ponies reduces both apparent digestibility of dietary cellulose and cellulose fermentation by faeces and isolated caecal and colonic contents

Inclusion of extra fat in the diet of horses, at the expense of an iso-energetic amount of non-structural carbohydrates, has been shown to decrease the apparent digestibility of the various dietary fiber fractions, but the mechanism was unknown. It was hypothesized that inclusion of extra fat in the diet depresses the caecal and/or colon microbial degradation of fiber, leading to a decrease in fiber digestion. The hypothesis was tested using six ponies fed either low fat or a high fat ration. In the ponies, the high fat ration lowered apparent NDFom digestibility by 0.089. The 12 ponies were killed and intestinal contents isolated to be used as inoculum with in vitro gas production technique. In general, groups mean maximum gas production from either cellulose or xylan by caecal, colon and faecal bacteria was lower when the ponies had been fed the high fat diet. Cumulative gas production by caecal fluid with xylan as substrate after 20 h of incubation was depressed when the donor animals had been fed the high fat diet. With cellulose as substrate, gas production by caecal contents was lowered by on average 20% after fat feeding of the ponies. There was a diet effect of cell-free caecal fluid on gas production from cellulose by a standard inoculum: fat feeding had an inhibitory impact. It is concluded that fat feeding in ponies inhibits microbial activity in the caecum, which in turn leads to a decrease in fiber digestibility.

Diabetes preventive gluten‐free diet decreases the number of caecal bacteria in non‐obese diabetic mice

A gluten-free diet reduces the incidence of diabetes mellitus in non-obese diabetic (NOD) mice, but the mechanism is not known. The aim of this study was to examine the possible influence of the diet on the caecal bacterial flora, which may affect the intestinal physiology and mediate disease prevention. Two groups of NOD mice from the age of 3 weeks were fed either a gluten-free diet or a standard diet. Each diabetic mouse, when diagnosed, along with a non-diabetic mouse from the same diet group and two non-diabetic mice from the alternate diet group were euthanized and sampled for classical bacteriological examination. Nine out of 19 (47%) standard-fed mice and 1 out of 19 (5%) gluten-free-fed mice developed diabetes (p < 0.01). Mice on the gluten-free diet had significantly fewer aerobically (p < 0.01) and microaerophilically (p < 0.001) cultivated bacteria in their intestines than standard-fed mice. Non-diabetic mice also had significantly fewer microa erophilic and anaerobic bacteria than diabetic mice (p < 0.05). These differences were primarily due to a difference in the Gram-positive flora. The gluten-free diet compared to the standard diet both qualitatively and quantitatively substantially altered the composition of the caecal bacterial flora in NOD mice. Although Gram-positive bacteria might influence the beta cells through certain digestive products, it is more likely to assume that any effect on diabetes incidence is immunological.

Protein recycling in growing rabbits: contribution of microbial lysine to amino acid metabolism

To study the absorption of microbial lysine in growing rabbits, a labelled diet (supplemented with (15)NH4Cl) was administered to six animals (group ISOT); a control group (CTRL, four rabbits) received a similar, but unlabelled, diet. Diets were administered for 30 d. An additional group of six animals were fed the unlabelled diet for 20 d and then the labelled diet for 10 d while wearing a neck collar to avoid caecotrophy (group COLL), in order to discriminate it from direct intestinal absorption. At day 30 animals were slaughtered and caecal bacteria and liver samples taken. The (15)N enrichment in amino acids of caecal bacteria and liver were determined by GC-combustion/isotope ratio MS. Lysine showed a higher enrichment in caecal microflora (0.925 atom% excess, APE) than liver (0.215 APE) in group ISOT animals, confirming the double origin of body lysine: microbial and dietary. The COLL group showed a much lower enrichment in tissue lysine (0.007 (se 0.0029) APE for liver). Any enrichment in the latter animals was due to direct absorption of microbial lysine along the digestive tract, since recycling of microbial protein (caecotrophy) was avoided. In such conditions liver enrichment was low, indicating a small direct intestinal absorption. From the ratio of [(15)N]lysine enrichment between liver and bacteria the contribution of microbes to body lysine was estimated at 23 %, with 97 % of this arising through caecotrophy. Absorption of microbial lysine through caecotrophy was 119 (se 4.0) mg/d, compared with 406 (se 1.8) mg/d available from the diet. This study confirms the importance of caecotrophy in rabbit nutrition (15 % of total protein intake).

In vitro fermentation of fructo-oligosaccharides and transgalacto-oligosaccharides by adapted and unadapted bacterial populations from the gastrointestinal tract of piglets

An in vitro study was performed to investigate the fermentation of fructo-oligosaccharides (FOS) and transgalacto-oligosaccharides (TOS) by bacteria harvested from the gastrointestinal tract of piglets. In addition, the apparent ileal digestibility of FOS and TOS was measured. Thirty piglets were fed either a semi-synthetic control diet or the control diet supplemented with 40 g FOS or 40 g TOS per kg ( n = 10). After 29 days, the piglets were killed and the gastrointestinal contents collected for the in vitro experiment and chemical analysis. The results demonstrated that bacteria from the stomach were nearly incapable of degrading FOS and TOS, whereas bacteria from the distal small intestine to some extend fermented FOS and TOS. Fermentation of FOS and TOS with bacteria from the stomach and distal small intestine was not affected by the dietary treatment of the piglets. Bacteria from the caecum and mid colon of the piglets showed the highest capacity to degrade FOS and TOS in vitro and the microbiota seemed to adapt to the dietary FOS. Caecal bacteria from piglets fed the FOS diet had tendencies to increased production rate of organic acids ( P < 0.1), propionic acid ( P < 0.1) and valeric acid ( P < 0.1) and significantly higher production rate of butyric acid ( P < 0.05) from FOS as compared with bacteria from piglets fed the control and TOS diet. Colonic bacteria from piglets fed the FOS diet also had significantly higher production rates of butyric acid ( P < 0.05) and capronic acid ( P < 0.01). In addition, significantly lower molar proportions of acetic acid ( P < 0.05) and propionic acid ( P < 0.05), and a significantly higher molar proportion of capronic acid ( P < 0.05) were observed for colonic bacteria from piglets fed the FOS diet as compared with the control diet. Fermentation of TOS by bacteria from the caecum and mid colon was generally not affected by the dietary treatment of the piglets. It was estimated that the capacity for microbial degradation of the dietary FOS and TOS during passage of the stomach and small intestine of the piglets was approximately a proportion of 0.20 for FOS and 0.16 for TOS. The coefficient of apparent ileal digestibility (CAID) was 0.57 (range 0.39–0.89) for FOS and 0.56 (range 0.31–0.82) for TOS. In conclusion, a proportion between 0.20 and 0.60 of FOS and TOS are degraded by the microbiota in the small intestine of piglets and the microbiota of the large intestine adapt to the administration of FOS in the feed.

Reduced ratio of protective versus proinflammatory cytokine responses to commensal bacteria in HLA-B27 transgenic rats.

Germ-free HLA-B27 transgenic (TG) rats do not develop colitis, but colonization with specific pathogen-free (SPF) bacteria induces colitis accompanied by immune activation. To study host-dependent immune responses to commensal caecal bacteria we investigated cytokine profiles in mesenteric lymph node (MLN) cells from HLA-B27 TG versus nontransgenic (non-TG) littermates after in vitro stimulation with caecal bacterial lysates (CBL). Supernatants from CBL-stimulated unseparated T- or B- cell-depleted MLN cells from HLA-B27 TG and non-TG littermates were analysed for IFN-gamma, IL-12, TNF, IL-10 and TGF-beta production. Our results show that unfractionated TG MLN cells stimulated with CBL produced more IFN-gamma, IL-12 and TNF than did non-TG MLN cells. In contrast, CBL-stimulated non-TG MLN cells produced more IL-10 and TGF-beta. T cell depletion abolished IFN-gamma and decreased IL-12 production, but did not affect IL-10 and TGF-beta production. Conversely, neither IL-10 nor TGF-beta was produced in cultures of B cell-depleted MLN. In addition, CD4(+) T cells enriched from MLN of HLA-B27 TG but not from non-TG rats produced IFN-gamma when cocultured with CBL-pulsed antigen presenting cells from non-TG rats. Interestingly, IL-10 and TGF-beta, but not IFN-gamma, IL-12 and TNF were produced by MLN cells from germ-free TG rats. These results indicate that the colitis that develops in SPF HLA-B27 TG rats is accompanied by activation of IFN-gamma-producing CD4(+) T cells that respond to commensal bacteria. However, B cell cytokine production in response to components of commensal intestinal microorganisms occurs in the absence of intestinal inflammation.

Influences of probiotic bacteria on organic acid production by pig caecal bacteria in vitro.

The mechanism of action of probiotics is largely unknown. A potential mechanism should be to increase the production of short-chain fatty acids (SCFA), known modulators of gut functions, by the bacterial ecosystem in the large intestine. The present paper reviews our recent studies in which the capacity of probiotic bacteria to increase the production of SCFA by pig caecal bacteria was investigated using batch-culture and continuous-culture techniques. All four commercial probiotic preparations and three strains of probiotic bacteria dose-dependently accelerated the net production of SCFA, succinic acid and lactic acid without changing the acid profile, and slowed the net production of NH4. Effects on organic acid production did not vary among different probiotic species. Neither probiotic preparations nor probiotic bacteria affected the organic acid production from glucose, gastric mucin, starch or lactose, or organic acids produced:added saccharide. Glucose abolished these effects of probiotic preparations. However, the capacity of probiotics to increase SCFA production was not modified by gastric mucin, starch or lactose. These results indicate that probiotic bacteria increase SCFA production by accelerating the breakdown of carbohydrates that are resistant to indigenous bacteria, and suggest that the concept of prebiotics in terms of SCFA production as a measure of probiotic function is arguable.

Effect of caprylic, capric and oleic acid on growth of rumen and rabbit caecal bacteria

Effect of caprylic, capric and oleic acid on growth of rumen and rabbit caecal bacteria

Colonization Capabilities of Environmental Pseudomonads and anEscherichia coliIntestinal Isolate in Two Different Continuous-Flow Models of the Murine Intestinal Tract

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Reduction of caecal Listeria monocytogenes in Leghorn chicks following treatment with a competitive exclusion culture (PREEMPT)

Day-of-hatch Leghorn chicks were treated by oral gavage with PREEMPT, a continuous-flow competitive exclusion culture containing broiler caecal bacteria, followed by an oral challenge with Listeria monocytogenes, to determine the effects of PREEMPT on L. monocytogenes caecal colonization. Increased (P < 0.001) concentrations of caecal propionic acid in control chicks compared with PREEMPT-treated chicks at 3 days of age were indicative of the establishment of the PREEMPT bacteria. Caeca from control chicks at 7 days after the oral challenge with L. monocytogenes contained mean 3.4 +/- 1.4 log cfu g-1 of caecal content, while caeca from PREEMPT-treated chicks contained no detectable Listeria. Enrichment for L. monocytogenes resulted in 100% of caeca from control chicks testing culture-positive for L. monocytogenes, while none of the caeca from PREEMPT-treated chicks were culture-positive. The results indicated that prophylactic treatment of newly hatched chicks with PREEMPT significantly reduced caecal colonization by L. monocytogenes.

In vitro 14C-amino acid fermentation by CF3, a characterized continuous-flow competitive exclusion culture of caecal bacteria.

Competition for growth-limiting nutrients by broiler caecal bacteria and Salmonella has been suggested as one factor associated with decreased Salmonella caecal colonization. The amino acids arginine, aspartic acid, serine and threonine have been indicated as Salmonella growth-limiting nutrients. Broiler caecal bacteria maintained in a continuous-flow culture (CF3) were used as inoculum for media containing 14C-arginine, 14C-aspartic acid, 14C-serine or 14C-threonine. The 14C-labelled amino acids, except 14C-arginine, were metabolized to lactic, formic, acetic, propionic and butyric acids. In glucose-based media, 72%, 72% and 33% of the radiolabel from aspartic acid, serine and threonine, respectively, were detected in organic acids. Fermentation without glucose resulted in 48%, 50% and 71% of the radiolabel from aspartic acid, serine and threonine, respectively, being detected in organic acids. Results indicated that the early establishment of CF3 in young chicks may result in the depletion of growth-limiting amino acids and, therefore, reduction of Salmonella colonization.

Fermentation of radiolabelled substrates by batch cultures of caecal microflora maintained in a continuous‐flow culture*

Glucose- and lactose-based media containing either 14C-labelled glucose, galactose, lactose or lactic acid were inoculated with anaerobic cultures of chicken caecal bacteria maintained for 121 d in a continuous-flow (CF) culture. The culture was previously shown to reduce Salmonella colonization in the caeca of chicks inoculated with the culture and the reduction was associated with increases in volatile fatty acids. The distributions of 14C were determined among the fermentation products, especially acetic, propionic and lactic acids. After 12 h of incubation and fermentation, variations were observed in the total amounts of 14C, from each 14C-labelled substrate, detected as acetic and propionic acids in the glucose- and lactose-based media, respectively: 92.9 and 89.4% of 14C-glucose, 77.0 and 44.0% of 14C-galactose, 0.0 and 76.9% of 14C-lactose, and 76.5 and 93.2% of lactic acid in the two media, respectively. The results from this study indicate that carbohydrate metabolism by the CF culture was a major source of acetic and propionic acids and that lactic acid was an important metabolic intermediate for the synthesis of the volatile fatty acids.

Effect of Vitamin Restriction on Caecal Bacteria and Short-Chain Fatty Acid Concentrations in Rats

Effect of Vitamin Restriction on Caecal Bacteria and Short-Chain Fatty Acid Concentrations in Rats

Effect of Vitamin Restriction on Caecal Bacteria and Short-Chain Fatty Acid Concentrations in Rats

Food restriction and intestinal bacteria had been reported to have effects on the physiological processes of laboratory animals. Therefore, a study was carried out on the effect of vitamin restriction on the caecal bacteria and short-chain fatty acid (SCFA) concentrations in Wistar rats. In rats fed ad libitum with a purified diet with a 0.3 per cent vitamin mixture, concentrations of bifidobacteria increased significantly (P<0.05) compared with animals fed a 1 per cent and 2 per cent vitamin diet. There was also a trend of increased lactobacilli, but this was not significant. Overgrowth of aerobic bacteria such as enterobacteria and enterococci was not found in the 0.3 per cent group. SCFA concentrations were reduced, but not significantly, in the 0.3 per cent group compared with the 1 per cent and 2 per cent groups. Rats fed a 50 per cent restricted diet containing 1 per cent vitamin mixture had significantly increased concentrations of lactobacilli (P<0.001) and bifidobacteria (P<0.05). In the 2 per cent vitamin regimen only, lactobacilli increased in the 50 per cent restricted group, but not significantly. Significantly decreased concentrations (P<0.01) of staphylococci were found in the animals fed 50 per cent restricted diets compared with the ad libitum groups. SCFA concentrations were reduced (P<0.01) by food restriction with both the 1 and 2 per cent vitamin diets. Growth of caecal lactobacilli was stimulated more by calorie restriction, and growth of bifidobacteria was stimulated more by vitamin restriction. The enhanced growth of fermentative bacteria in the caecal microbiota of rats by vitamin and calorie restriction is discussed in relation to microbial competition or antagonism. Keywords: Vitamin and calorie restriction, Caecal bacteria, Bifidobacteria, Lactobacilli, Short-chain fatty acids, Rat

An in vitro model for studies on bacterial interactions in the avian caecum.

An in vitro intermittent-flow model was developed for studying bacterial interactions in the avian caecum. The model provides a closer simulation of caecal conditions than others described previously but does not require elaborate instrumentation. In preliminary trials, growth of caecal bacteria from an adult chicken was shown to be inhibitory to both Salmonella infantis and entero-haemorrhagic Escherichia coli.