Effect of high-fiber and high-oil diets on the fecal flora of swine

Enhanced anaerobic treatment of swine wastewater with exogenous granular sludge: Performance and mechanism

Anaerobic biotechnology has been widely used to the treatment of swine wastewater, but its organic loading rate is far lower than the expected. In this study, the fatigue effect was observed for indigenous anaerobic sludge (IAS) of anaerobic digestion system treating swine wastewater. On the contrary, the enhancement effect was demonstrated for exogenous granular sludge (EGS) originated from the internal circulation reactor treating pulping wastewater. The results showed the anaerobic digestion of swine wastewater with acclimatized EGS was much better than with IAS, 10th-day COD removal efficiency of 85% and 37% respectively. The better performance of acclimatized EGS was attributed to the more efficient degradation of volatile fatty acids (VFAs) as well as a stronger tolerance to the ammonia inhibition of swine wastewater. Revealed by molecular techniques, the acclimatized EGS contained more abundant syntrophic bacteria and methanogens than IAS. These functional microbes colonized in the acclimatized EGS could overcome the fatigue effect of IAS which contained a similar microbial community to pig gastrointestinal tract microbes. This study provides a feasible and promising way to enhance the efficiency of anaerobic digestion of swine wastewater.

Biochemical Changes and Biological Origin of Key Odor Compound Generations in Pig Slurry during Indoor Storage Periods: A Pyrosequencing Approach

Production of odors is a complex process. Many bacterial species are involved in the production of an extensive array of key odor compounds in stored pig slurry. Understanding of basic microbial communities and their role during storage periods is an essential way to control and prevent the odors generations. In this aspect, the pig slurry samples were taken directly from deep pits of finisher pig building every two weeks, their biochemical changes were analysed, and the indigenous bacterial communities that involve in offensive odor producing compounds were identified. The SCFA, BCFA, phenols, and indoles levels altered drastically in the slurry during storage periods. The COD, BOD, SS, P₂O₅, TKN, and NH₄-N were increased in the stored slurry. Bacterial ecology indicates Firmicutes and Bacteroidetes phyla were dominantly found in pig slurry. Odorants produced in pig slurry were correlated with bacterial communities. Phenols, indoles, SCFA, and BCFA productions were positively correlated with bacteria species which comes under phyla of Firmicutes and Bacteroidetes. It seems that bacterial species under Firmicutes and Bacteroidetes phyla play an important role in the offensive odor compounds production. Taken together, the prevention of these phyla bacterial growth and early discharge of pig slurry might reduce the offensive odor production.

Body growth, intestinal morphology and microflora of quail on diets supplemented with micronised wheat fibre

1. Particle size reductions of fibre-rich materials alter structure, functional and digestive properties. To determine the effects of using fibre as an additive in Japanese quail rations on performance and gut physiology, a trial using micronised wheat fibre (MWF) at levels of 0.0, 5, 10 and 15 g/kg in feed was conducted. 2. Growth rate and feed efficiency were significantly improved when diets contained MWF while feed intake was not affected by levels of the fibre. As MWF content increased, the relative weight of gizzard and gastrointestinal tract (GIT) significantly increased whereas liver relative weight significantly decreased. 3. MWF inclusion significantly increased relative length of gut segments, villi height, villus thickness, the villi height to crypt depth proportion in jejunum and ileum and the number of goblet cells in different parts of intestine. 4. Tibia weight, length and ash content were increased linearly with rising MWF inclusion. Litter moisture was affected by MWF inclusions in a quadratic manner. The colony forming unit (CFU/g) of Streptococci spp. in ileal digesta was decreased with increasing MWF inclusion levels in the diet. 5. In conclusion, MWF can be used as a feed additive in quail diets and its inclusion in feed resulted in better performance, beneficial changes in intestinal microbial counts and improvements in small intestine morphology.

Microbiota in fermented feed and swine gut

Development of alternatives to antibiotic growth promoters (AGP) used in swine production requires a better understanding of their impacts on the gut microbiota. Supplementing fermented feed (FF) in swine diets as a novel nutritional strategy to reduce the use of AGP and feed price, can positively affect the porcine gut microbiota, thereby improving pig productivities. Previous studies have noted the potential effects of FF on the shift in benefit of the swine microbiota in different regions of the gastrointestinal tract (GIT). The positive influences of FF on swine gut microbiota may be due to the beneficial effects of both pre- and probiotics. Necessarily, some methods should be adopted to properly ferment and evaluate the feed and avoid undesired problems. In this mini-review, we mainly discuss the microbiota in both fermented feed and swine gut and how FF influences swine gut microbiota.

Identification of metabolic signatures linked to anti-inflammatory effects of Faecalibacterium prausnitzii

Faecalibacterium prausnitzii is an anti-inflammatory commensal bacterium identified on the basis of human clinical data. The mechanisms underlying its beneficial effects are still unknown. Gnotobiotic mice harboring F. prausnitzii (A2-165) and Escherichia coli (K-12 JM105) were subjected to 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced acute colitis. The inflammatory colitis scores and a gas chromatography-time of flight (GC/TOF) mass spectrometry-based metabolomic profile were monitored in blood, ileum, cecum, colon, and feces in gnotobiotic mice. The potential anti-inflammatory metabolites were tested in vitro. We obtained stable E. coli and F. prausnitzii-diassociated mice in which E. coli primed the gastrointestinal tract (GIT), allowing a durable and stable establishment of F. prausnitzii. The disease activity index, histological scores, myeloperoxidase (MPO) activity, and serum cytokine levels were significantly lower in the presence of F. prausnitzii after TNBS challenge. The protective effect of F. prausnitzii against colitis was correlated to its implantation level and was linked to overrepresented metabolites along the GIT and in serum. Among 983 metabolites in GIT samples and serum, 279 were assigned to known chemical reactions. Some of them, belonging to the ammonia (α-ketoglutarate), osmoprotective (raffinose), and phenolic (including anti-inflammatory shikimic and salicylic acids) pathways, were associated with a protective effect of F. prausnitzii, and the functional link was established in vitro for salicylic acid. We show for the first time that F. prausnitzii is a highly active commensal bacterium involved in reduction of colitis through in vivo modulation of metabolites along the GIT and in the peripheral blood.

IMPORTANCE

Inflammatory bowel diseases (IBD) are characterized by low proportions of F. prausnitzii in the gut microbiome. This commensal bacterium exhibits anti-inflammatory effects through still unknown mechanisms. Stable monoassociated rodents are actually not a reproducible model to decipher F. prausnitzii protective effects. We propose a new gnotobiotic rodent model providing mechanistic clues. In this model, F. prausnitzii exhibits protective effects against an acute colitis and a protective metabolic profile is linked to its presence along the digestive tract. We identified a molecule, salicylic acid, directly involved in the protective effect of F. prausnitzii. Targeting its metabolic pathways could be an attractive therapeutic strategy in IBD.

Temporal changes and the effect of subtherapeutic concentrations of antibiotics in the gut microbiota of swine

The use of antibiotics in swine production for the purpose of growth promotion dates back to the 1950s. Despite this long history of use, the exact mechanism(s) responsible for the growth-promoting effects of antibiotics in swine remain largely unknown. It is believed, however, that growth promotion is due to antibiotics having a direct impact on the gut microbiota. In this study, the effect of two antibiotics on the swine gut microbiota over a 19-week monitoring period was investigated using Illumina-based sequencing. A shift in the relative abundance of several taxa and in 26 operational taxonomic units (OTUs) was observed in pigs fed subtherapeutic concentrations of tylosin (44-11 mg kg(-1) feed). Only minor alterations were noted with the administration of chlortetracycline at 5.5 mg kg(-1) feed. The most notable changes in the relative abundance of taxa and OTUs were noted between suckling piglets and postweaned pigs. Diversity was also reduced in the gut microbiota of suckling piglets as measured using the Shannon, Chao1, and phylogenetic diversity indices. These results show that the effect of antibiotics on the swine gut microbiota is variable based on dosage and duration and that the swine gut microbiota exhibits considerable resilience to long-term changes due to antibiotic perturbations.

Use of pigs as a potential model for research into dietary modulation of the human gut microbiota

The human intestinal microbial ecosystem plays an important role in maintaining health. A multitude of diseases including diarrhoea, gastrointestinal inflammatory disorders, such as necrotising enterocolitis (NEC) of neonates, and obesity are linked to microbial composition and metabolic activity. Therefore, research on possible dietary strategies influencing microbial composition and activity, both preventive and curative, is being accomplished. Interest has focused on pre- and probiotics that stimulate the intestinal production of beneficial bacterial metabolites such as butyrate, and beneficially affect microbial composition. The suitability of an animal model to study dietary linked diseases is of much concern. The physiological similarity between humans and pigs in terms of digestive and associated metabolic processes places the pig in a superior position over other non-primate models. Furthermore, the pig is a human-sized omnivorous animal with comparable nutritional requirements, and shows similarities to the human intestinal microbial ecosystem. Also, the pig has been used as a model to assess microbiota–health interactions, since pigs exhibit similar syndromes to humans, such as NEC and partly weanling diarrhoea. In contrast, when using rodent models to study diet–microbiota–health interactions, differences between rodents and humans have to be considered. For example, studies with mice and human subjects assessing possible relationships between the composition and metabolic activity of the gut microbiota and the development of obesity have shown inconsistencies in results between studies. The present review displays the similarities and differences in intestinal microbial ecology between humans and pigs, scrutinising the pig as a potential animal model, with regard to possible health effects.

Use of Saccharomyces cerevisiae fermentation product on growth performance and microbiota of weaned pigs during Salmonella infection

Anaerobically fermented yeast products are a rich source of nutritional metabolites, mannanoligosaccharides, and β-glucans that may optimize gut health and immunity, which can translate into better growth performance and a reduced risk of foodborne pathogens. The objective of this study was to quantify the effects of Saccharomyces cerevisiae fermentation product (Diamond V Original XPC) inclusion in nursery diets on pig performance and gastrointestinal microbial ecology before, during, and after an oral challenge with Salmonella. Pigs (n = 40) were weaned at 21 d of age, blocked by BW, and assigned in a 2 × 2 factorial arrangement consisting of diet (control or 0.2% XPC) and inoculation (sterile broth or Salmonella). Pigs were fed a 3-phase nursery diet (0 to 7 d, 7 to 21 d, and 21 to 35 d) with ad libitum access to water and feed. On d 14, pigs were orally inoculated with 10(9) cfu of Salmonella enterica serovar Typhimurium DT104 or sterile broth. During d 17 to 20, all pigs were treated with a 5 mg/kg of BW intramuscular injection of ceftiofur-HCl. Growth performance and alterations in the gastrointestinal microbial ecology were measured during preinoculation (PRE; 0 to 14 d), sick (SCK; 14 to 21 d), and postinoculation (POST; 21 to 35 d). Body weight and ADG were measured weekly. Rectal temperature (RT) was measured weekly during PRE and POST, and every 12 h during SCK. Diet had no effect on BW, ADG, or RT during any period (P = 0.12 to 0.95). Inclusion of XPC tended (P < 0.10) to increase Salmonella shedding in feces during SCK. Consumption of XPC altered the composition of the gastrointestinal microbial community, resulting in increased (P < 0.05) populations of Bacteroidetes and Lactobacillus after Salmonella infection. Pigs inoculated with Salmonella had decreased ADG and BW, and increased RT during SCK (P < 0.001). Furthermore, fecal Salmonella cfu (log(10)) was modestly correlated (P = 0.002) with BW (r = -0.22), ADFI (r = -0.27), ADG (r = -0.36), G:F (r = -0.18), and RT (r = 0.52) during SCK. After antibiotic administration, all Salmonella-infected pigs stopped shedding. During POST, an interaction between diet and inoculation (P = 0.009) on ADG indicated that pigs infected with Salmonella grew better when eating XPC than the control diet. The addition of XPC to the diets of weanling pigs resulted in greater compensatory BW gains after infection with Salmonella than in pigs fed conventional nursery diets. This increase in BW gain is likely associated with an increase in beneficial bacteria within the gastrointestinal tract.

Health-beneficial effects of probiotics: Its mode of action

It is now widely recognized that probiotics have health-beneficial effects on humans and animals. Probiotics should survive in the intestinal tract to exert beneficial effects on the host's health. To keep a sufficient level of probiotic bacteria in the gastrointestinal tract, a shorter interval between doses may be required. Although adherence to the intestinal epithelial cell and mucus is not a universal property of probiotics, high ability to adhere to the intestinal surface might strongly interfere with infection of pathogenic bacteria and regulate the immune system. The administration of probiotic Lactobacillus stimulated indigenous Lactobacilli and the production of short-chain fatty acids. This alteration of the intestinal environment should contribute to maintain the host's health. The immunomodulatory effects of probiotics are related to important parts of their beneficial effects. Probiotics may modulate the intestinal immune response through the stimulation of certain cytokine and IgA secretion in intestinal mucosa. The health-beneficial effects, in particular the immunomodulation effect, of probiotics depend on the strain used. Differences in indigenous intestinal microflora significantly alter the magnitude of the effects of a probiotic. Specific probiotic strains suitable for each animal species and their life stage as well as each individual should be found.

Nutritional influences on some major enteric bacterial diseases of pig

There are several enteric bacterial diseases and conditions of pigs that require control to prevent overt disease, to reduce morbidity and mortality, and to improve the efficiency of production. Traditionally, veterinarians, feed manufacturers and producers have relied upon antibiotics and minerals (for example, ZnO, CuSO4) in diets for a large part of this control. However, recent trends, particularly in Europe, are to reduce antimicrobial use and seek alternative or replacement strategies for controlling enteric bacterial diseases. The majority of these strategies rely on 'nutrition', taken in its broadest sense, to reduce the susceptibility of pigs to these diseases. Evidence to date suggests that specific dietary interventions, for example feeding very highly-digestible diets based on cooked white rice, can reduce the proliferation of a number of specific enteric bacterial infections, such as post-weaning colibacillosis. No simple and universal way to reduce susceptibility to pathogens in the gastrointestinal tract has been identified, and the underlying basis for many of the reported positive effects of 'nutrition' on controlling enteric infections lacks robust, scientific understanding. This makes it difficult to recommend dietary guidelines to prevent or reduce enteric bacterial diseases. Furthermore, some diseases, such as porcine intestinal spirochaetosis caused by Brachyspira pilosicoli, are sometimes associated with other pathogens (co-infections). In such cases, each pathogen might have different nutrient requirements, ecological niches and patterns of metabolism for which a variety of dietary interventions are needed to ameliorate the disease. Greater understanding of how 'nutrition' influences gut epithelial biology and immunobiology, and their interactions with both commensal and pathogenic bacteria, holds promise as a means of tackling enteric disease without antimicrobial agents. In addition, it is important to consider the overall system (i.e. management, housing, welfare) of pig production in the context of controlling enteric bacterial diseases.

DGGE and 16S rDNA sequencing analysis of bacterial communities in colon content and feces of pigs fed whole crop rice

The effect of feeding whole crop rice (WCR) to growing-finishing pigs at three levels 0 (Control), 10% and 20% on bacterial communities in colon content and feces was analyzed using 16S rDNA-based techniques. Amplicons of the V6-V8 variable regions of bacterial 16S rDNA were analyzed by denaturing gradient gel electrophoresis (DGGE), cloning and sequencing. The total number of DGGE bands and Shannon index of diversity for feces samples were higher in the pigs fed WCR-containing diets compared with the control, while a decrease trend was observed in these two parameters for colon content samples with the inclusion of WCR in the diets, although statistical differences were not significant. In general, the intestinal bacterial communities were prone to form the cluster for pig fed the same diet. Feeding of WCR induced the presence of special DGGE band with the sequence showing 99% similarity to that of Lactobacillus reuteri (DSM 20016T). The sequences of seven amplicons in total nine clones showed less than 97% similarity with those of previously identified or unidentified bacteria, suggesting that most bacteria in gastrointestinal tracts have not been cultured or identified. The results suggest that the diet containing WCR did not affect the major groups of bacteria, but stimulated the growth of L. reuteri-like species.

Two high-amylose maize starches with different amounts of resistant starch vary in their effects on fermentation, tissue and digesta mass accretion, and bacterial populations in the large bowel of pigs

Four groups of young pigs (n 6) were fed a diet containing 50% maize starch as either a highly digestible waxy starch (control; 0% amylose) or one of three resistant starch (RS) diets, namely a high-amylose maize starch (HAMS; 85% amylose), this starch subjected to hydrothermal treatment (HTHAMS; 85% amylose), or a blend of HAMS and HTHAMS included in equal amounts, for 21 d. Food intake and live weight at the end of the study were similar among the four groups. Ileal starch digestibility was lower in pigs fed the three RS diets but was greater for HAMS(88%) than for HTHAMS (70%; P<0.05). Faecal output and large bowel digesta mass, and concentrations and pools of individual and total SCFA were higher (by about two- to threefold; all P<0.05) and digesta pH lower (by about 1 unit, all P<0.001) in pigs fed either HAMS or HTHAMS compared to the controls. These differences in biomarkers were seen along the length of the large bowel. Colon length was 0.5-0.9 m longer (19-35%) in pigs fed the high-RS diets relative to those fed the highly digestible starch diet (P<0.05). Faecal and proximal colonic lactobacilli and bifidobacteria numbers were higher (by 1 and 3 log units; P< 0.05) in pigs fed the HAMS or HTHAMS diets. Although both high-amylose starches promoted fermentation throughout the large bowel, the data suggest that the effects of HTHAMS may be more pronounced in the distal region compared to those of HAMS.

Antibiotic growth promoters in agriculture: history and mode of action

This report will review the history of antibiotic growth promoter (AGP) use in the animal industry, concerns about development of antimicrobial resistance, and response in the European Union and United States to these concerns. A brief description of the history of legislation regarding feed use of antimicrobials in Denmark and the experience of animal producers following the 1998 ban will serve to illustrate the consequences on animal performance and health of withdrawing the approval for this use. The biological basis for antibiotic effects on animal growth efficiency will consider effects on intestinal microbiota and effects on the host animal and will use the germ-free animal to illustrate effects of the conventional microflora. The probability that no single compound will replace all of the functions of antimicrobial growth promoters will be considered, and methods to consolidate and analyze the enlarging database will be discussed.

Isolation, growth on prebiotics and probiotic potential of novel bifidobacteria from pigs

Bifidobacteria were isolated from the faeces of pigs of various ages and examined for their potential use as probiotics in combination with di- and oligosaccharides. Ninty-six per cent of the isolates were found to have characteristics in common with Bifidobacterium boum, B. thermophilum and B. choerinum. B. thermophilum was most commonly isolated from sows, whereas most of the other strains were isolated from piglets. A few strains of each species were able to grow in the presence of air. A microplate assay was modified to allow comparison of growth on different substrates. Di- and oligosaccharides considered to promote bifidobacteria were screened for their ability to support growth of selected isolates in vitro. Growth on these substrates varied within and between species. Of the fructose oligosaccharides tested, Actilight P supported the best growth of the widest range of strains. The strains which grew best on the disaccharide lactulose were related to B. choerinum and some of these strains grew on xylo-oligosaccharides. It seems that prebiotic di- and oligosaccharides may have both a species and intra-species/strain selective effect. B. choerinum appeared to be well adapted to the gut of pre-weaned piglets.

Seasonal variation in microbial communities and organic malodor indicator compound concentrations in various types of swine manure storage systems

Anaerobic manure storage systems are one of the major contributors to the odor and environmental pollution associated with swine (Sus scrofa) production systems. The microbial ecology of manure storage systems and the relationships between microbial communities and odor production are largely unknown. In this study, we used community fatty acid methyl ester (FAME) analysis to generate lipid profiles to assess seasonal differences among microbial communities inhabiting various types of outdoor swine manure storage systems. Concurrently, we measured manure concentrations of several malodor indicator compounds as well as pH, temperature, and solids content. Principal components analysis (PCA) showed that there are differences in FAME profiles among the swine manure storage systems examined and most of the variation was in the relative abundance of 18:0, 18:1omega7t, 18:1omega7c/omega9t/omega12t, and 16:1omega7t/i15:0 2OH FAMEs. The PCA of the FAME profiles revealed that the phototrophic systems were more similar to each other and that the nonphototrophic systems were more similar to each other than they were to phototrophic lagoons. There were seasonal changes in the FAME profiles in the phototrophic systems and the concrete nonphototrophic basin (CNPB), and in one phototrophic system, the FAME profiles more closely resembled a CNPB FAME profile during the winter than the other phototrophic lagoons. In the phototrophic lagoon systems, there was a direct correlation between the abundance of the FAMEs identified in the PCA and manure concentrations of phenol, p-cresol, and 4-ethyl phenol. In the CNPB, there was a negative correlation between the total phenolics concentration and the 18:1omega7t FAME. Our results indicate that community FAME profiles could be used as a diagnostic tool for obtaining preliminary evidence that management practices are altering the system's microbial community to one that favors less air pollution potential.

Culture-independent analysis of gut bacteria: the pig gastrointestinal tract microbiota revisited

The phylogenetic diversity of the intestinal bacterial community in pigs was studied by comparative 16S ribosomal DNA (rDNA) sequence analysis. Samples were collected from a total of 24 pigs representing a variety of diets, ages, and herd health status. A library comprising 4,270 cloned 16S rDNA sequences obtained directly by PCR from 52 samples of either the ileum, the cecum, or the colon was constructed. In total, 375 phylotypes were identified using a 97% similarity criterion. Three hundred nine of the phylotypes (83%) had a <97% sequence similarity to any sequences in the database and may represent yet-uncharacterized bacterial genera or species. The phylotypes were affiliated with 13 major phylogenetic lineages. Three hundred four phylotypes (81%) belonged to the low-G+C gram-positive division, and 42 phylotypes (11.2%) were affiliated with the Bacteroides and Prevotella group. Four clusters of phylotypes branching off deeply within the low-G+C gram-positive bacteria and one in the Mycoplasma without any cultured representatives were found. The coverage of all the samples was 97.2%. The relative abundance of the clones approximated a lognormal distribution; however, the phylotypes detected and their abundance varied between two libraries from the same sample. The results document that the intestinal microbial community is very complex and that the majority of the bacterial species colonizing the gastrointestinal tract in pigs have not been characterized.

Development of antibiotic resistance and options to replace antimicrobials in animal diets

As there is a risk of developing antibiotic resistance, a number of commonly-used antimicrobial growth promoters have been banned in the EU member states. This decision has put new emphasis on using the diet to control enteric bacterial infections of pigs. Dietary carbohydrates constitute a major proportion of diets for pigs, and the carbohydrate fraction has a diverse composition, with different properties in the gastrointestinal tract, some of which are of importance to gut health. Findings from different studies indicate that dietary carbohydrate composition influences the expression of swine dysentery and infection with nematode worms after experimental challenge with Brachyspira hyodesenteriae and Oesophagostumum dentatum respectively. In both cases the type, amount and physico-chemical properties of the carbohydrates entering the large intestine played an important role in the infection, and emerging data suggest a synergism between different porcine pathogens. There is also increasing evidence that the feed structure, which relates to the type of plant material in the diet and the way it is processed, can be used to reduce Salmonella prevalence at the herd level. However, it should be stressed that using the diet to manage gut health is not straightforward, since the expression of a pathogen in many cases requires the presence of other components of the commensal biota.

Changes in bacterial community structure in the colon of pigs fed different experimental diets and after infection with Brachyspira hyodysenteriae

Bacterial communities in the large intestines of pigs were compared using terminal restriction fragment length polymorphism (T-RFLP) analysis targeting the 16S ribosomal DNA. The pigs were fed different experimental diets based on either modified standard feed or cooked rice supplemented with dietary fibers. After feeding of the animals with the experimental diets for 2 weeks, differences in the bacterial community structure in the spiral colon were detected in the form of different profiles of terminal restriction fragments (T-RFs). Some of the T-RFs were universally distributed, i.e., they were found in all samples, while others varied in distribution and were related to specific diets. The reproducibility of the T-RFLP profiles between individual animals within the diet groups was high. In the control group, the profiles remained unchanged throughout the experiment and were similar between two independent but identical experiments. When the animals were experimentally infected with Brachyspira hyodysenteriae, causing swine dysentery, many of the T-RFs fluctuated, suggesting a destabilization of the microbial community.

Molecular analysis of the microbial diversity present in the colonic wall, colonic lumen, and cecal lumen of a pig

Random clones of 16S ribosomal DNA gene sequences were isolated after PCR amplification with eubacterial primers from total genomic DNA recovered from samples of the colonic lumen, colonic wall, and cecal lumen from a pig. Sequences were also obtained for cultures isolated anaerobically from the same colonic-wall sample. Phylogenetic analysis showed that many sequences were related to those of Lactobacillus or Streptococcus spp. or fell into clusters IX, XIVa, and XI of gram-positive bacteria. In addition, 59% of randomly cloned sequences showed less than 95% similarity to database entries or sequences from cultivated organisms. Cultivation bias is also suggested by the fact that the majority of isolates (54%) recovered from the colon wall by culturing were related to Lactobacillus and Streptococcus, whereas this group accounted for only one-third of the sequence variation for the same sample from random cloning. The remaining cultured isolates were mainly Selenomonas related. A higher proportion of Lactobacillus reuteri-related sequences than of Lactobacillus acidophilus- and Lactobacillus amylovorus-related sequences were present in the colonic-wall sample. Since the majority of bacterial ribosomal sequences recovered from the colon wall are less than 95% related to known organisms, the roles of many of the predominant wall-associated bacteria remain to be defined.

The application of ecological principles and fermentable fibers to manage the gastrointestinal tract ecosystem

Because diet can influence the structure and functions of the gastrointestinal tract, there are opportunities for using diet as a "management tool" to affect the resident microbiota. Fermentable fibers increase the densities of beneficial bacteria and stimulate growth and functions of the healthy intestine. Recent findings show that after acute diarrhea, the use of an oral electrolyte solution with the fermentable fiber oligofructose accelerates recovery of beneficial bacteria, reduces the relative abundance of detrimental bacteria, stimulates mucosal growth and enhances digestive and immune functions. This review will focus on how the principles of stream ecology can be applied to better understand the distribution of bacteria along the length of the gastrointestinal tract, the effect of diarrhea on the gastrointestinal ecosystem and how fermentable fibers can be used as a "management tool" to promote gastrointestinal health in normal states and during recovery from diarrhea.

Methanogenesis in monogastric animals

Studies of methanogenic bacteria present in monogastric animals are still scarce. Methanogens have been isolated from faeces of rat, horse, pig, monkey, baboon, rhinoceros, hippopotamus, giant panda, goose, turkey and chicken. The predominant methanogen in all except the chicken and turkey is species of Methanobrevibacterium. The chicken and turkey harbour species of Methanogenium. In pig the population of methanogenic bacteria is more than 30 times as dense in the distal colon as in the caecum. This finding is in agreement with the finding that the rate of methane production is much higher in the colon than in the ceacum. The amount of methane excreted clearly seems to depend on the amount of non-starch polysaccharide intake.The directly measured methane production rate in pigs is from 3.3 to 3.8 times lower than the amount expected from stoichiometric estimates. These data, together with data showing that only small net amounts of hydrogen and small amounts of methane are produced in the ceacum and proximal colon where the microbial activity is high, clearly indicate that hydrogen sinks other than methane production are involved in hydrogen removal in the hindgut of pigs and probably also in other monogastric animals.Methane production by monogastric animals is lower than methane production by ruminants. However, methane production by large herbivorous monogastric animals such as horses, mules and asses is substantial (up to 80 l per animal per day). Methane production by rodents and avians is low. In general, methane production by wild animals is lower than methane production by domestic animals. It is concluded that the contribution of monogastric animals to the global methane emission is negligible, as it only represent about 5% of the total methane emission by domestic and wild animals of 80 Tg per year.

Digestibility of energy, protein, fat and non-starch polysaccharides in mixed diets: comparative studies between man and the rat

The apparent digestibility of energy, protein, fat and non-starch polysaccharides (NSP) of low and high dietary fibre (DF) mixed diets were studied in three series of experiments with man and the rat. Low DF diets were used as control diets in each experimental series and the DF level was increased by adding fruits and vegetables (Study 1), citrus fibre concentrate (Study 2) and insoluble barley fibre (Study 3). In Study 3 the high DF diet was fed at two protein levels. There was in most cases good agreement between the digestibility of energy between man and the rat, with the digestibility of energy of the low DF control diets of 0.941-0.950 in man compared with 0.933-0.952 in the rat and of the high DF diets of 0.897-0.931 in man and 0.865-0.920 in the rat. The biggest difference in digestible energy between the two species was found for the diet enriched with fruits and vegetables (0.032 absolute units) and citrus fibre concentrate (0.025 absolute units). Apparent digestibility of protein was slightly lower in man than in the rat for all diets in Studies 1 and 2. In Study 3, however, apparent digestibility of protein was consistently lower in man than in the rat with differences in absolute digestibilities between the two species varying from 0.023 (high DF/high protein) to 0.071 (high DF/low protein). The digestibility of fat was the same in man and in the rat in all but the high DF diet of Study 2. The rat appears to have a lower capacity to digest fibre polysaccharides than man and the digestibility of NSP was consistently lower in the rat than in man. The biggest difference between the two species was found for the diets in Study 2 where the digestibility of NSP in man was measured to be 0.774-0.885 compared with only 0.501-0.517 in the rat. For the other diets the differences in NSP digestibility were 0.077-0.137 absolute units. In spite of some differences between man and the rat in their ability to digest nutrients the various diets are ranked in the same order by the two species.

Strategies in pathogenesis: mechanistic specificity in the detection of generic signals

The virulence genes of the plant pathogen Agrobacterium tumefaciens are induced by more than 40 low-molecular-weight phenolic compounds. The prevailing opinion is that (i) wound-derived phenols produced on breach of the integrity of the cell wall act as the initiating signal in a series of events which results in host cell transformation, and (ii) a classical membrane receptor, putatively VirA, is responsible for the recognition of all such phenolic inducers. Here, we argue that the discovery of the subset of inducers that are relatives of the dehydrodiconiferyl alcohol glucoside (DCG) growth factors redirects our attention to work on the plant wound as a site of cell division, and suggests that we further explore the implications of early work on the relationship between transformation efficiency and the status of the cell cycle of the host. In addition, we argue that the significant structural diversity allowed in the para position of the phenol ring of inducers suggests that a receptor-ligand interaction based solely on structural recognition is insufficient, but that recognition followed by a specific proton transfer event may be sufficient to explain vir induction activity. Hence, the specificity of the response of A. tumefaciens may be a consequence of the features required for a chemical reaction to occur on the receptor surface. Finally, we review affinity labelling studies which exploit this phenol detection mechanism and which provide evidence that the phenol receptor may be other than VirA, the sensory kinase of the two component regulatory system implicated in Agrobacterium virulence.(ABSTRACT TRUNCATED AT 250 WORDS)

Characteristics of a new cellulolytic Clostridium sp. isolated from pig intestinal tract

Gram-positive, spore-forming, motile, cellulolytic rods were isolated from 10(7) dilutions of pig fecal samples. The pigs had previously been fed pure cultures of the ruminal cellulolytic organism Clostridium longisporum. Isolates formed terminal to subterminal spores, and a fermentable carbohydrate was required for growth. Besides cellulose, the isolates utilized cellobiose, glycogen, maltose, and starch. However, glucose, fructose, sucrose, pectin, and xylose were not used as energy sources. Major fermentation products included formate and butyrate. The isolates did not digest proteins from gelatin or milk. Unlike C. longisporum, which has limited ability to degrade cell wall components from grasses (switchgrass, bromegrass, and ryegrass), the swine isolates were equally effective in degrading these components from both alfalfa and grasses. The extent of degradation was equal to or better than that observed with the predominant ruminal cellulolytic organisms. On the basis of morphology, motility, spore formation, fermentation products, and the ability to hydrolyze cellulose, the isolates are considered to be a new species of the genus Clostridium. It is unclear whether C. longisporum played a role in the establishment or occurrence of this newly described cellulolytic species. This is the first report of a cellulolytic Clostridium sp. isolated from the pig intestinal tract.

Enumeration by a miniaturized method of Escherichia coli, Streptococcus bovis and enterococci as indicators of the origin of faecal pollution of waters

Counts of Escherichia coli, faecal streptococci and enterococci were made on faecal specimens from human and animal origin and urban raw sewage waters, with microtiter plates containing selective substances. Escherichia coli was more numerous than faecal streptococci and enterococci in 80% of the samples regardless of the origin. Consequently the use of the ratio E. coli/faecal streptococci to distinguish human from animal origin of faecal pollution is questionable. Enterococcus faecalis was predominant in human and poultry faeces, Streptococcus bovis was typical of the bovine faeces and to a lesser extent also of pig faeces whereas Enterococcus durans, Ent. hirae and Ent. faecium did not characterize any faecal source. Streptococcus bovis could be distinguished in the microtiter plate by its inability to reduce triphenyl tetrazolium chloride (TTC) in the medium.

Dietary modification of potential vitamin K supply from enteric bacterial menaquinones in rats

Rats given a low-fibre diet based on boiled white rice developed symptoms of severe vitamin K deficiency within 23 d. Inclusion of autoclaved black-eye beans (Vigna unguiculata) in the diet prevented the bleeding syndrome. To test the hypothesis that deficiency resulted from low phylloquinone intake exacerbated by inadequate production of menaquinones by the enteric bacteria, a follow-up experiment was carried out in which groups of rats were given an all-rice diet, a rice + beans diet or a stock diet. Rats on the all-rice diet had significantly lower faecal concentrations of the main menaquinone-producing bacterial species (Bacteroides fragilis and Bacteroides vulgatus) than animals on either of the other two diets. This coupled with the much lower faecal output on this diet suggests that total menaquinone production was low for the all-rice diet. The alterations in faecal flora were associated with several significant changes in caecal metabolism. Rats given the stock diet had much shorter caecal transit times and a considerably greater proportion of butyric acid in volatile fatty acid end-products than did rats on either of the other two diets.

In vitro total-gas, CH4, H2, volatile fatty acid, and lactate kinetics studies on luminal contents from the small intestine, cecum, and colon of the pig

Two experiments were conducted to assess differences in fermentative activities of digesta obtained from various regions of the pig gastrointestinal tract. In experiment 1, the contents of small intestines, ceca, and colons of 110-kg pigs were collected, diluted twofold, and incubated for 2 h at 37 degrees C. In experiment 2, colonic samples from 16,100-kg pigs were similarly treated, except that the incubation period was 5 h. Total gas (gas pressure), CH4, H2, lactate, formate, acetate, propionate, butyrate, valerate, and isovalerate were measured in experiment 1. Only the gas variables were measured in experiment 2. Statistically significant differences (P greater than 0.05) were not observed among the gas production rate estimates across the small-intestinal, cecal, and colonic regions in experiment 1. Furthermore, all the small-intestinal samples and half the cecal samples assayed in experiment 1 were nonmethanogenic. The mean methanogenic and total-gas production rate estimates for the colonic samples in experiment 1 were 0.052 ml g of wet contents-1 h-1 and 1.7 ml of total gas g of wet contents-1 h-1, respectively. No differences in the methanogenic rate estimates were detected between the proximal, middle, and distal thirds of the pig colons (P greater than 0.05). The volatile fatty acid and lactate molar percentages measured in experiment 1 were consistent with previously published observations. Hydrogen accumulated to the greatest extent (7 microM on average) in the in vitro incubations of small-intestinal contents, whereas the H2 concentrations ranged from 0.5 to 1 microM for the incubated cecal and colonic samples in experiment 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Enumeration of selected anaerobic bacterial groups in cecal and colonic contents of growing-finishing pigs

Selected anaerobic bacterial groups in cecal and colonic contents of clinically healthy pigs fed a corn-soybean meal production diet were determined at sacrifice after 4, 8, and 11 weeks on feed, corresponding to intervals within the growing-finishing growth period. By using ruminal fluid-based media, the densities of the culturable anaerobic population; the cellulolytic, pectin-fermenting, pectin-hydrolyzing, xylan-fermenting; and the xylan-hydrolyzing, sulfate-reducing, and methanogenic bacterial populations were estimated. An analysis of variance was performed on these bacterial group variables to examine the effects of phase (weeks on feed), site (cecum or colon), or the interaction of phase with site. The population of total anaerobic bacteria was twice as dense in the colon as it was in the cecum (2 x 10(10) versus 1 x 10(10)/g [wet weight]; P = 0.001). The proportion of cellulolytic bacteria was lower at 4 weeks on feed than at 8 or 11 weeks (23 versus 32%; P = 0.026), while the proportion of pectin-fermenting bacteria depended on the interaction of phase with site (P = 0.021). The numbers of sulfate-reducing bacteria were significantly higher in the colon than in the cecum (6 x 10(7) versus 3 x 10(7); P = 0.014), as were methanogenic bacteria (19 x 10(7) versus 0.6 x 10(7); P = 0.0002). The remaining bacterial groups were stable with respect to phase and site. The results suggest that except for density differences, the microbial communities of the pig cecum and colon are similar in composition throughout the growing-finishing phase.

Fecapentaenes and their precursors throughout the bowel--results of an autopsy study

The fecapentaenes are potent mutagens found in the stool of some humans and pigs. These compounds are produced by Bacteroides species in the gut from an uncharacterized family of precursor compounds, and have been postulated to pose a risk of human colorectal cancer. To better understand fecapentaene production in vivo, and to determine if excreted levels measured in epidemiologic studies are representative of the entire colon, fecapentaenes were assayed from multiple sites in the bowel in an autopsy study of 16 humans and 2 pigs. An indirect measurement of fecapentaene precursors was also made. Colonic concentrations of fecapentaenes and precursors varied widely between individuals, but were consistent for each individual throughout the colon. In addition, the measurements of rectal contents, assumed to approximate values in excreted stool, were equivalent to measurements from the colon.