Enzymatically modified starch up-regulates expression of incretins and sodium-coupled monocarboxylate transporter in jejunum of growing pigs

Dietary effects on the host are mediated via modulation of the intestinal mucosal responses. The present study investigated the effect of an enzymatically modified starch (EMS) product on the mucosal expression of genes related to starch digestion, sugar and short-chain fatty acid (SCFA) absorption and incretins in the jejunum and cecum in growing pigs. Moreover, the impact of the EMS on hepatic expression of genes related to glucose and lipid metabolism, and postprandial serum metabolites were assessed. Barrows (n=12/diet; initial BW 29 kg) were individually fed three times daily with free access to a diet containing either EMS or waxy corn starch as control (CON) for 10 days. The enzymatic modification led to twice as many α-1,6-glycosidic bonds (~8%) in the amylopectin fraction in the EMS in comparison with the non-modified native waxy corn starch (4% α-1,6-glycosidic bonds). Linear discriminant analysis revealed distinct clustering of mucosal gene expression for EMS and CON diets in jejunum. Compared with the CON diet, the EMS intake up-regulated jejunal expression of sodium-coupled monocarboxylate transporter (SMCT), glucagon-like peptide-1 (GLP1) and gastric inhibitory polypeptide (GIP) (P<0.05) and intestinal alkaline phosphatase (ALPI) (P=0.08), which may be related to greater luminal SCFA availability, whereas cecal gene expression was unaffected by diet. Hepatic peroxisome proliferator-activated receptor γ (PPARγ) expression tended (P=0.07) to be down-regulated in pigs fed the EMS diet compared with pigs fed the CON diet, which may explain the trend (P=0.08) of 30% decrease in serum triglycerides in pigs fed the EMS diet. Furthermore, pigs fed the EMS diet had a 50% higher (P=0.03) serum urea concentration than pigs fed the CON diet potentially indicating an increased use of glucogenic amino acids for energy acquisition in these pigs. Present findings suggested the jejunum as the target site to influence the intestinal epithelium and altered lipid and carbohydrate metabolism by EMS feeding.     

Comparative analysis of the ileal bacterial composition of post-weaned pigs fed different high-quality protein sources

To further understand the contribution of feedstuff ingredients to gut health in swine, gut histology and intestinal bacterial profiles associated with the use of two high-quality protein sources, microbially enhanced soybean meal (MSBM) and Menhaden fishmeal (FM) were assessed. Weaned pigs were fed one of three experimental diets: (1) basic diet containing corn and soybean meal (Negative Control (NEG)), (2) basic diet + fishmeal (FM; Positive Control (POS)) and (3) basic diet + MSBM (MSBM). Phase I POS and MSBM diets (d 0 to d 7 post-wean) included FM or MSBM at 7.5%, while Phase II POS and MSBM diets (d 8 to d 21) included FM or MSBM at 5.0%. Gastrointestinal tissue and ileal digesta were collected from euthanised pigs at d 21 (eight pigs/diet) to assess gut histology and intestinal bacterial profiles, respectively. Data were analysed using Proc Mixed in SAS, with pig as the experimental unit and pig (treatment) as the random effect. Histological and immunohistochemical analyses of stomach and small intestinal tissue using haematoxylin–eosin, Periodic Acid Schiff/Alcian blue and inflammatory cell staining did not reveal detectable differences in host response to dietary treatment. Ileal bacterial composition profiles were obtained from next-generation sequencing of PCR generated amplicons targeting the V1 to V3 regions of the 16S rRNA gene. Lactobacillus-affiliated sequences were found to be the most highly represented across treatments, with an average relative abundance of 64.0%, 59.9% and 41.80% in samples from pigs fed the NEG, POS and MSBM diets, respectively. Accordingly, the three most abundant Operational Taxonomic Units (OTUs) were affiliated to Lactobacillus, showing a distinct abundance pattern relative to dietary treatment. One OTU (SD_Ssd_00001), most closely related to Lactobacillus amylovorus, was found to be more abundant in NEG and POS samples compared to MSBM (23.5% and 35.0% v. 9.2%). Another OTU (SD_Ssd_00002), closely related to Lactobacillus johnsonii, was more highly represented in POS and MSBM samples compared to NEG (14.0% and 15.8% v. 0.1%). Finally, OTU Sd_Ssd-00011, highest sequence identity to Lactobacillus delbrueckii, was found in highest abundance in ileal samples from MSBM-fed pigs (1.9% and 3.3% v. 11.3, in POS, NEG and MSBM, respectively). There was no effect of protein source on bacterial taxa to the genus level or diversity based on principal component analysis. Dietary protein source may provide opportunity to enhance presence of specific members of Lactobacillus genus that are associated with immune-modulating properties without altering overall intestinal bacterial diversity.     

Enzymatically Modified Starch Ameliorates Postprandial Serum Triglycerides and Lipid Metabolome in Growing Pigs

Developing host digestion-resistant starches to promote human health is of great research interest. Chemically modified starches (CMS) are widely used in processed foods and although the modification of the starch molecule allows specific reduction in digestibility, the metabolic effects of CMS have been less well described. This short-term study evaluated the impact of enzymatically modified starch (EMS) on fasting and postprandial profiles of blood glucose, insulin and lipids, and serum metabolome in growing pigs. Eight jugular-vein catheterized pigs (initial body weight, 37.4 kg; 4 months of age) were fed 2 diets containing 72% purified starch (EMS or waxy corn starch (control)) in a cross-over design for 7 days. On day 8, an 8-hour meal tolerance test (MTT) was performed with serial blood samplings. Besides biochemical analysis, serum was analysed for 201 metabolites through targeted mass spectrometry-based metabolomic approaches. Pigs fed the EMS diet showed increased (P<0.05) immediate serum insulin and plasma glucose response compared to pigs fed the control diet; however, area-under-the-curves for insulin and glucose were not different among diets. Results from MTT indicated reduced postprandial serum triglycerides with EMS versus control diet (P<0.05). Likewise, serum metabolome profiling identified characteristic changes in glycerophospholipid, lysophospholipids, sphingomyelins and amino acid metabolome profiles with EMS diet compared to control diet. Results showed rapid adaptations of blood metabolites to dietary starch shifts within 7 days. In conclusion, EMS ingestion showed potential to attenuate postprandial raise in serum lipids and suggested constant alteration in the synthesis or breakdown of sphingolipids and phospholipids which might be a health benefit of EMS consumption. Because serum insulin was not lowered, more research is warranted to reveal possible underlying mechanisms behind the observed changes in the profile of serum lipid metabolome in response to EMS consumption.     

Changes in the Rumen Epimural Bacterial Diversity of Beef Cattle as Affected by Diet and Induced Ruminal Acidosis

Little is known about the nature of the rumen epithelial adherent (epimural) microbiome in cattle fed different diets. Using denaturing gradient gel electrophoresis (DGGE), quantitative real-time PCR (qPCR), and pyrosequencing of the V3 hypervariable coding region of 16S rRNA, epimural bacterial communities of 8 cattle were profiled during the transition from a forage to a high-concentrate diet, during acidosis, and after recovery. A total of 153,621 high-quality gene sequences were obtained, with populations exhibiting less taxonomic variability among individuals than across diets. The bacterial community composition exhibited clustering (P < 0.03) by diet, with only 14 genera, representing >1% of the rumen epimural population, differing (P ≤ 0.05) among diets. During acidosis, levels of Atopobium, Desulfocurvus, Fervidicola, Lactobacillus, and Olsenella increased, while during the recovery, Desulfocurvus, Lactobacillus, and Olsenella reverted to levels similar to those with the high-grain diet and Sharpea and Succinivibrio reverted to levels similar to those with the forage diet. The relative abundances of bacterial populations changed during diet transition for all qPCR targets except Streptococcus spp. Less than 5% of total operational taxonomic units (OTUs) identified exhibited significant variability across diets. Based on DGGE, the community structures of epithelial populations differed (P ≤ 0.10); segregation was most prominent for the mixed forage diet versus the grain, acidotic challenge, and recovery diets. Atopobium, cc142, Lactobacillus, Olsenella, RC39, Sharpea, Solobacterium, Succiniclasticum, and Syntrophococcus were particularly prevalent during acidosis. Determining the metabolic roles of these key genera in the rumens of cattle fed high-grain diets could define a clinical microbial profile associated with ruminal acidosis.     

Changes in bacterial populations in the ileum of pigs fed low-phosphorus diets supplemented with different sources of fermentable carbohydrates

An experiment was conducted to evaluate the effects of differently fermentable carbohydrates on changes in bacterial populations in the ileum of growing pigs fed low-phosphorus (P) diets. Eight barrows (mean surgery BW 36 ± 0.9 kg) were fitted with simple T-cannulae at the distal ileum and were assigned to one of four dietary treatments: maize-soybean meal based control diet (CD), or 0.75 of CD supplemented with 0.25 lignocellulose, maize starch and high-methylated apple-pectin, respectively. Total bacterial cell counts as well as cell counts of Lactobacillus spp., Lactobacillus reuteri, Lactobacillus amylovorus/Lactobacillus sobrius, Lactobacillus mucosae, Enterococcus spp., Enterococcus faecium, Enterococcus faecalis, bifidobacteria, Clostridium coccoides cluster, Clostridium leptum cluster, Bacteroides–Prevotella–Porphyrmonas group and Enterobacteriaceae were determined by quantitative realtime PCR in DNA extracts of ileal digesta. Denaturing gradient gel electrophoresis (DGGE) of DNA fragments, generated by PCR targeting total or Lactobacillus spp. 16S rDNA, was used to estimate the bacterial diversity in the ileum. Lignocellulose supplementation tended (P<0.1) to increase cell counts of total bacteria in faeces compared with the control. Ileal bacterial populations responded differently to carbohydrate addition. Maize starch supplementation strongly stimulated the growth of total lactobacilli and Lactobacillus species (P≤0.05). Lignocellulose, in turn, enhanced the numbers of bifidobacteria, but reduced those of L. amylovorus compared with the control (P<0.05). Finally, pectin tended to increase the cell numbers of L. amylovorus/L. sobrius and the Bacteroides–Prevotella–Porphyrmonas group compared with the control (P<0.1). DGGE analysis revealed increased band numbers for total bacteria in the ileum of animals fed the lignocellulose and maize starch supplemented diets, while pectin reduced total bacterial (P<0.1) and Lactobacillus spp. diversity (P<0.05) compared with the control, as determined with the Shannon's index. Ileal VFA concentrations were decreased by pectin, while lignocellulose decreased faecal VFA concentrations. In conclusion, ileal bacterial populations and diversity are susceptible to changes in the carbohydrate composition of the diet. However, these changes were not related to major differences in the number of total bacteria in ileal digesta and faeces, but rather to changes in the bacterial species composition and their metabolic activity.     

Effects of resistant starch on behaviour,satiety-related hormones and metabolites in growing pigs

Resistant starch (RS) has been suggested to prolong satiety in adult pigs. The present study investigated RS-induced changes in behaviour, satiety-related hormones and metabolites in catheterized growing pigs to explore possible underlying mechanisms for RS-induced satiety. In a cross-over design with two 14-day periods, 10 pigs (initial BW: 58 kg) were assigned to two treatments comprising diets containing either 35% pregelatinized starch (PS) or 34% retrograded starch (RS). Diets were isoenergetic on gross energy. Pigs were fed at 2.8× maintenance. Postprandial plasma response of satiety-related hormones and metabolites was measured at the end of each period using frequent blood sampling. Faecal and urinary energy losses were measured at the end of each period. Behaviour was scored 24 h from video recordings using scan sampling. Energy digestibility and metabolizability were ~6% lower in RS compared with PS diet (P<0.001), and metabolizable energy (ME) intake was ~3% lower in RS-fed than in PS-fed pigs (P<0.001). RS-fed pigs showed less feeder-directed (P=0.001) and drinking (P=0.10) behaviours than PS-fed pigs throughout the day. Postprandial peripheral short-chain fatty acid (SCFA) levels were higher in RS-fed than in PS-fed pigs (P<0.001). Postprandial glucose and insulin responses were lower in RS-fed than in PS-fed pigs (P<0.001). Triglyceride levels were higher in RS-fed than in PS-fed pigs (P<0.01), and non-esterified fatty acid levels did not differ between diets (P=0.90). Glucagon-like peptide-1 (GLP-1) levels were lower in RS-fed than in PS-fed pigs (P<0.001), and peptide tyrosine tyrosine (PYY) levels did not differ between diets (P=0.90). Blood serotonin levels were lower (P<0.001), whereas monoamine oxidase activity (P<0.05) and tryptophan (P<0.01) levels were higher in RS-fed than in PS-fed pigs. Despite a lower ME intake, RS seemed to prolong satiety, based on behavioural observations. Possible underlying mechanisms for RS-induced satiety include increased 24 h plasma SCFA levels, and decreased postprandial glucose and insulin responses. GLP-1 and PYY seemed not to play a role in RS-induced satiety. Low blood serotonin levels in RS-fed pigs suggested a difference in intestinal serotonin release between treatments. Increased postprandial plasma triglyceride levels corresponded with increased SCFA levels, but it is unclear whether triglycerides may have signalled satiety in RS-fed pigs.     

Analysis of bacterial community shifts in the gastrointestinal tract of pigs fed diets supplemented with β-glucan from Laminaria digitata,Laminaria hyperborea and Saccharomyces cerevisiae

This study was designed to evaluate the effects of algal and yeast β-glucans on the porcine gastrointestinal microbiota, specifically the community of Lactobacillus, Bifidobacterium and coliforms. A total of 48 pigs were fed four diets over a 28-day period to determine the effect that each had on these communities. The control diet consisted of wheat and soya bean meal. The remaining three diets contained wheat and soya bean meal supplemented with β-glucan at 250 g/tonne from Laminaria digitata, Laminaria hyperborea or Saccharomyces cerevisiae. Faecal samples were collected from animals before feeding each diet and after the feeding period. The animals were slaughtered the following day and samples were collected from the stomach, ileum, caecum, proximal colon and distal colon. Alterations in Lactobacillus in the gastrointestinal tract (GIT) were analysed using denaturing gradient gel electrophoresis (DGGE) profiles generated by group-specific 16S rRNA gene PCR amplicons. Plate count analysis was also performed to quantify total coliforms. DGGE profiles indicated that all β-glucan diets provoked the emergence of a richer community of Lactobacillus. The richest community of lactobacilli emerged after feeding L. digitata (LD β-glucan). Plate count analysis revealed that the L. hyperborea (LH β-glucan) diet had a statistically significant effect on the coliform counts in the proximal colon in comparison with the control diet. β-glucan from L. digitata and S. cerevisiae also generally reduced coliforms but to a lesser extent. Nevertheless, the β-glucan diets did not significantly reduce levels of Lactobacillus or Bifidobacterium. DGGE analysis of GIT samples indicated that the three β-glucan diets generally promoted the establishment of a more varied range of Lactobacillus species in the caecum, proximal and distal colon. The LH β-glucan had the most profound reducing effect on coliform counts when compared with the control diet and diets supplemented with L. digitata and S. cerevisiae β-glucans.     

Feed intake patterns nor growth rates of pigs are affected by dietary resistant starch,despite marked differences in digestion

Current feed evaluation systems often assume that fermented starch (i.e. resistant starch (RS)) yields less energy than digested starch. However, growth rates of pigs fed low and high RS diets are often the same when feed is available ad libitum. This may be explained by its effect on digestive processes changing feeding behavior, and consequently energy utilization. This study aims to investigate the effect of RS on nutrient digestion and digesta passage rate in pigs, in combination with its effect on feeding behavior and growth performance under ad libitum conditions. In experiment 1, 20 male pigs (40 ± 2.82 kg) were fed diets containing either 50% waxy maize starch (low in RS (LRS)) or high-amylose maize starch (high in RS (HRS)), and soluble and insoluble indigestible markers. After 14 days of adaptation to the diets, pigs were fed hourly to reach steady state (6 h), dissected, and digesta were collected from eight segments. From the collected samples, nutrient digestion and passage rate of the solid and liquid digesta fraction were determined. In experiment 2, 288 pigs (80 ± 0.48 kg; sex ratio per pen 1 : 1; boar : gilt) were housed in groups of 6. Pigs were ad libitum-fed one of the experimental diets, and slaughtered at approximately 115 kg. Feed intake, growth and carcass parameters were measured. Ileal starch digestibility was greater for LRS-fed than for HRS-fed pigs (98.0% v. 74.0%; P < 0.001), where the additional undigested starch in HRS-fed pigs was fermented in the large intestine. No effects of RS on digesta passage rate of the solid or liquid digesta fraction and on feeding behavior were observed. Growth rate and feed intake did not differ between diets, whereas feed efficiency of HRS-fed pigs was 1%-unit higher than that of LRS-fed pigs (P = 0.041). The efficiency of feed used for carcass gain did not differ between diets indicating that the difference in feed efficiency was determined by the non-carcass fraction. Despite a 30% greater RS intake (of total starch) with HRS than with LRS, carcass gain and feed efficiency used for carcass gain were unaffected. RS did not affect digesta passage rate nor feeding behavior suggesting that the difference in energy intake between fermented and digested starch is compensated for post-absorptively. Our results indicate that the net energy value of fermented starch currently used in pig feed evaluation systems is underestimated and should be reconsidered.     

Diversity and Succession of the Intestinal Bacterial Community of the Maturing Broiler Chicken

The diversity of bacterial floras in the ilea and ceca of chickens that were fed a vegetarian corn-soy broiler diet devoid of feed additives was examined by analysis of 1,230 partial 16S rRNA gene sequences. Nearly 70% of sequences from the ileum were related to those of Lactobacillus, with the majority of the rest being related to Clostridiaceae (11%), Streptococcus (6.5%), and Enterococcus (6.5%). In contrast, Clostridiaceae-related sequences (65%) were the most abundant group detected in the cecum, with the other most abundant sequences being related to Fusobacterium (14%), Lactobacillus (8%), and Bacteroides (5%). Statistical analysis comparing the compositions of the different 16S rRNA libraries revealed that population succession occurred during some sampling periods. The significant differences among cecal libraries at 3 and 7 days of age, at 14 to 28 days of age, and at 49 days of age indicated that successions occurred from a transient community to one of increasing complexity as the birds aged. Similarly, the ileum had a stable bacterial community structure for birds at 7 to 21 days of age and between 21 to 28 days of age, but there was a very unique community structure at 3 and 49 days of age. It was also revealed that the composition of the ileal and cecal libraries did not significantly differ when the birds were 3 days old, and in fact during the first 14 days of age, the cecal microflora was a subset of the ileal microflora. After this time, the ileum and cecum had significantly different library compositions, suggesting that each region developed its own unique bacterial community as the bird matured.     

Resistant starch reduces colonic and urinary p-cresol in rats fed a tyrosine-supplemented diet,whereas konjac mannan does not

The effect of resistant starch (RS) and konjac mannan (KM) to maintain and improve the large intestinal environment was compared. Wistar SPF rats were fed the following diets for 4 weeks: negative control diet (C diet), tyrosine-supplemented positive control diet (T diet), and luminacoid supplemented diets containing either high-molecular konjac mannan A (KMAT diet), low-molecular konjac mannan B (KMBT diet), high-amylose cornstarch (HAST diet), or heat-moisture-treated starch (HMTST diet). The luminacoid-fed group had an increased content of short-chain fatty acids in the cecum. HAS caused a significant decrease in p-cresol content in the cecum, whereas KM did not. Urinary p-cresol was reduced in the HAST group compared with the T group, but not the KM fed groups. Deterioration in the large intestinal environment was only improved completely in the HAST and HMTST groups, suggesting that RS is considerably more effective than KM in maintaining the large intestinal environment.     

Effects of cereal β-glucans and enzyme inclusion on the porcine gastrointestinal tract microbiota

This study was designed to evaluate the effect barley-based diets vs. oats based diets on levels of Lactobacillus, Bifidobacterium and Enterobacterium in the porcine gastrointestinal tract (GIT). In addition the effect of enzyme supplementation in both diets was explored. Twenty-eight boars were used in a 2 × 2 factorial arrangement and were assigned to 1 of 4 dietary treatments: barley-based (B) diet; barley-based diet plus an enzyme supplement (B + ES); oat-based (O) diet or oat-based diet plus an enzyme supplement (O + ES). The enzyme supplement contained endo-1,3-β-glucanase and endo-1,4-β-xylanase. Faecal samples were collected from the pigs prior to initiations of the experiment and at slaughter. At slaughter digesta samples were collected from the stomach, ileum, caecum, proximal and distal colon. Alterations in Lactobacillus species composition in the gastrointestinal tract (GIT) were analysed by genus-specific PCR – denaturing gradient gel electrophoresis (DGGE). DGGE profiles indicated that cereal source provoked shifts in Lactobacillus population. The most diverse populations of lactobacilli emerged after feeding the O diets. Enzymes inclusion altered the composition of Lactobacillus species prevalent throughout the GIT in animals fed the B diet, causing a shift in the dominant lactobacilli present in the caecum and proximal colon. No such effect was evident in animals fed the enzyme supplemented O + ES diet. Microbial plate counts revealed that the O diets gave rise to higher counts of Lactobacillus in the caecum and colon and Bifidobacterium counts in the ileum, caecum and colon than the B diets. The O diet caused a 2 log increase in Enterobacterium counts in the proximal colon, no such effects were observed in animals fed the B, the B + ES or the O + ES diets. Overall both O diets had a more positive influence on the counts of the beneficial microorganisms and richness of the Lactobacillus population in the porcine GIT.     

Effects of soluble corn bran arabinoxylans on cecal digestion, lipid metabolism, and mineral balance (Ca, Mg) in rats

The effects of soluble corn bran arabinoxylans on cecal digestion, lipid metabolism, and mineral utilization [calcium (Ca) and magnesium (Mg)] were investigated in rats adapted to semipurified diets. The diets provided either 710 g/kg wheat starch alone (control) or 610 g/kg wheat starch plus 100 g/kg corn soluble fiber (arabinoxylans) and either 0 or 2 g/kg cholesterol (control + cholesterol and arabinoxylans + cholesterol, respectively). Compared with rats fed the control diets, rats fed the arabinoxylan diets had significant cecal hypertrophy (+50% after 3 days of the fiber adaptation) and an accumulation of short-chain fatty acids, especially propionic acid (up to 45% in molar percentage). Arabinoxylans enhanced the cecal absorption of Ca and Mg (from 0.07 to 0.19 micromol/min for Ca and from 0.05 to 0.23 micromol/min for Mg). Mg balance was enhanced by arabinoxylans (+25%). The arabinoxylan diet markedly reduced the cholesterol absorption from 50% of ingested cholesterol in controls up to approximately 15% in rats adapted to the arabinoxylans diet. Arabinoxylans were effective in lowering plasma cholesterol (approximately -20%). There was practically no effect of the diets on cholesterol in d > 1.040 lipoproteins (high density lipoproteins) whereas arabinoxylans were very effective in depressing cholesterol in d < 1.040 lipoproteins (especially in triglyceride-rich lipoproteins). Corn fermentable fiber decreased the accumulation of cholesterol in the liver. In parallel, the arabinoxylan diet counteracted the downregulation of 3-hydroxy-3-methylglutaryl-CoA by cholesterol. These data suggest that arabinoxylans may have a great impact on intestinal fermentation, mineral utilization, and cholesterol metabolism.     

Potato powders prepared by successive cooking-process depending on resistant starch content affect the intestinal fermentation in rats

The effects of resistant starch (RS) in dry potato powders prepared by various processes on intestinal fermentation in rats were assessed. Rats were fed raw potato powder (RP), blanched potato powder (BP), steamed potato powder (SP), or drum-dried potato powder (DP) for 4 weeks. The cecal RS content was significantly higher in the RP group than in the control diet (CN) group and other dry potato powder groups. Cecum pH was significantly lower in the RP group compared to the CN group, and was also significantly lower than that in the SP, BP, and DP groups. Lactic acid bacteria levels in the RP group were significantly higher than those in the CN group, and levels in the SP group also increased relative to the control group. Lactobacillus levels in the RP group were higher than in the CN and other dry potato powder groups. Cecal short-chain fatty acid (SCFA) concentrations in the RP group followed by the SP group exhibited significantly higher levels relative to the control levels. Dry potato powders containing RS produced during the cooking process may represent a useful food material that increases intestinal concentrations of SCFA and enhances the growth of certain lactic acid bacteria.     

Transfer of blood urea nitrogen to cecal microbial nitrogen is increased by mannitol feeding in growing rabbits fed timothy hay diet

The presence of the fermentable sugar d-mannitol in the diet improves nitrogen (N) utilization in rabbits. To clarify the mechanism by which d-mannitol improves N utilization, we studied the effect of d-mannitol on the fate of blood urea N in growing rabbits. Growing rabbits received a control diet or a diet containing d-mannitol, which were formulated by adding 80 g/kg glucose or d-mannitol to timothy hay. After 9 days of feeding of the experimental diets, ¹⁵N-urea was administrated intravenously under anesthesia 1 h before slaughter. The blood urea level (concentration of both urea N (43.6% of the control group (CG), P < 0.05) and ¹⁵N (95% of the CG, P < 0.05) in blood serum) was reduced in the mannitol group. The concentration and amount of N, and ¹⁵N atom % excess in the contents of the cecum and colon were higher (P < 0.05) in the rabbits fed the mannitol diet than in rabbits fed the control diet, especially in the cecum. The consumption of mannitol caused bacterial proliferation in the cecum characterized by marked short-chain fatty acid production (165% of the CG, P < 0.05), decreased cecal ammonia N (73% of the CG, P < 0.05) and elevated cecal bacterial N (150% of the CG, P < 0.05). On the other hand, addition of d-mannitol to the diet decreased N (80% of the CG, P < 0.05) and ¹⁵N (77% of the CG, P < 0.05) excretion in the urine. These results indicate that d-mannitol increases the transfer of blood urea N to the large intestine, where it is used for bacterial N synthesis.     

Effects of diet type,developmental stage,and gut compartment in the gut bacterial communities of two <Emphasis Type="Italic">Cerambycidae species</Emphasis> (Coleoptera)

The gut bacterial community of wood-feeding beetles has been examined for its role on plant digestion and biocontrol method development. Monochamus alternatus and Psacothea hilaris, both belonging to the subfamily Lamiinae, are woodfeeding beetles found in eastern Asia and Europe and generally considered as destructive pests for pine and mulberry trees, respectively. However, limited reports exist on the gut bacterial communities in these species. Here, we characterized gut bacterial community compositions in larva and imago of each insect species reared with host tree logs and artificial diets as food sources. High-throughput 454 pyrosequencing of bacterial 16S rRNA gene revealed 225 operational taxonomic units (OTUs) based on a 97% sequences similarity cutoff from 138,279 sequence reads, the majority of which were derived from Proteobacteria (48.2%), Firmicutes (45.5%), and Actinobacteria (5.2%). The OTU network analysis revealed 7 modules with densely connected OTUs in specific gut samples, in which the distributions of Lactococcus-, Kluyvera-, Serratia-, and Enterococcus-related OTUs were distinct between diet types or developmental stages of the host insects. The gut bacterial communities were separated on a detrended correspondence analysis (DCA) plot and by c-means fuzzy clustering analysis, according to diet type. The results from this study suggest that diet was the main determinant for gut bacterial community composition in the two beetles.     

Dominant and diet-responsive groups of bacteria within the human colonic microbiota

The populations of dominant species within the human colonic microbiota can potentially be modified by dietary intake with consequences for health. Here we examined the influence of precisely controlled diets in 14 overweight men. Volunteers were provided successively with a control diet, diets high in resistant starch (RS) or non-starch polysaccharides (NSPs) and a reduced carbohydrate weight loss (WL) diet, over 10 weeks. Analysis of 16S rRNA sequences in stool samples of six volunteers detected 320 phylotypes (defined at >98% identity) of which 26, including 19 cultured species, each accounted for >1% of sequences. Although samples clustered more strongly by individual than by diet, time courses obtained by targeted qPCR revealed that ‘blooms'' in specific bacterial groups occurred rapidly after a dietary change. These were rapidly reversed by the subsequent diet. Relatives of Ruminococcus bromii (R-ruminococci) increased in most volunteers on the RS diet, accounting for a mean of 17% of total bacteria compared with 3.8% on the NSP diet, whereas the uncultured Oscillibacter group increased on the RS and WL diets. Relatives of Eubacterium rectale increased on RS (to mean 10.1%) but decreased, along with Collinsella aerofaciens, on WL. Inter-individual variation was marked, however, with >60% of RS remaining unfermented in two volunteers on the RS diet, compared to <4% in the other 12 volunteers; these two individuals also showed low numbers of R-ruminococci (<1%). Dietary non-digestible carbohydrate can produce marked changes in the gut microbiota, but these depend on the initial composition of an individual''s gut microbiota.     

Effects of alginate and resistant starch on feeding patterns,behaviour and performance in ad libitum-fed growing pigs

This study assessed the long-term effects of feeding diets containing either a gelling fibre (alginate (ALG)), or a fermentable fibre (resistant starch (RS)), or both, on feeding patterns, behaviour and growth performance of growing pigs fed ad libitum for 12 weeks. The experiment was set up as a 2×2 factorial arrangement: inclusion of ALG (yes or no) and inclusion of RS (yes or no) in the control diet, resulting in four dietary treatments, that is, ALG−RS− (control), ALG+RS−, ALG−RS+, and ALG+RS+. Both ALG and RS were exchanged for pregelatinized potato starch. A total of 240 pigs in 40 pens were used. From all visits to an electronic feeding station, feed intake and detailed feeding patterns were calculated. Apparent total tract digestibility of energy, dry matter (DM), and CP was determined in week 6. Pigs’ postures and behaviours were scored from live observations in weeks 7 and 12. Dietary treatments did not affect final BW and average daily gain (ADG). ALG reduced energy and DM digestibility (P<0.01). Moreover, ALG increased average daily DM intake, and reduced backfat thickness and carcass gain : digestible energy (DE) intake (P<0.05). RS increased feed intake per meal, meal duration (P<0.05) and inter-meal intervals (P=0.05), and reduced the number of meals per day (P<0.01), but did not affect daily DM intake. Moreover, RS reduced energy, DM and CP digestibility (P<0.01). Average daily DE intake was reduced (P<0.05), and gain : DE intake tended to be increased (P=0.07), whereas carcass gain : DE intake was not affected by RS. In week 12, ALG+RS− increased standing and walking, aggressive, feeder-directed, and drinking behaviours compared with ALG+RS+ (ALG×RS interaction, P<0.05), with ALG−RS− and ALG−RS+ in between. No other ALG×RS interactions were found. In conclusion, pigs fed ALG compensated for the reduced dietary DE content by increasing their feed intake, achieving similar DE intake and ADG as control pigs. Backfat thickness and carcass efficiency were reduced in pigs fed ALG, which also showed increased physical activity. Pigs fed RS changed feeding patterns, but did not increase their feed intake. Despite a lower DE intake, pigs fed RS achieved similar ADG as control pigs by increasing efficiency in DE use. This indicates that the energy utilization of RS in pigs with ad libitum access to feed is close to that of enzymatically digestible starch.     

Green kiwifruit modulates the colonic microbiota in growing pigs

Aims: To investigate whether green kiwifruit modulates the composition of colonic microbiota in growing pigs. Methods and Results: Thirty‐two pigs were fed the control diet or one of the three test diets containing either cellulose, freeze‐dried kiwifruit or kiwifruit fibre as the sole fibre source for 14‐day study. A Ward’s dendrogram of similarity cluster analysis on PCR‐DGGE gels revealed that inclusion of freeze‐dried kiwifruit and kiwifruit fibre into diets altered the bacterial community, indicating the presence of two distinct clusters. Quantification of different bacterial groups by qPCR demonstrated that pigs fed the freeze‐dried kiwifruit or kiwifruit fibre diets had a significantly higher number (P < 0·05) of total bacteria and Bacteroides group and a lower number of Enterobacteria and Escherichia coli group, as well as a greater ratio of Lactobacillus to Enterobacteria when compared to pigs fed the control or cellulose diets. Conclusions: Green kiwifruit, mainly because of fibre, modulated the colonic microbiota, leading to an improved intestinal environment in growing pigs. Significance and Impact of the Study: This is the first report regarding the effect of green kiwifruit on gut microbiota using the in vivo pig model. These results provide the first evidence of interaction between green kiwifruit and colonic microbiota.     

Fermentable non-starch polysaccharides increases the abundance of Bacteroides–Prevotella–Porphyromonas in ileal microbial community of growing pigs

Most plant-origin fiber sources used in pig production contains a mixture of soluble and insoluble non-starch polysaccharides (NSP). The knowledge about effects of these sources of NSP on the gut microbiota and its fermentation products is still scarce. The aim of this study was to investigate effects of feeding diets with native sources of NSP on the ileal and fecal microbial composition and the dietary impact on the concentration of short-chain fatty acids (SCFA) and lactic acid. The experiment comprised four diets and four periods in a change-over design with seven post valve t-cecum cannulated growing pigs. The four diets were balanced to be similar in NSP content and included one of four fiber sources, two diets were rich in pectins, through inclusion of chicory forage (CFO) and sugar beet pulp, and two were rich in arabinoxylan, through inclusion of wheat bran (WB) and grass meal. The gut microbial composition was assessed with terminal restriction fragment (TRF) length polymorphism and the abundance of Lactobacillus spp., Enterobacteriaceae, Bacteroides–Prevotella–Porphyromonas and the β-xylosidase gene, xynB, were assessed with quantitative PCR. The gut microbiota did not cluster based on NSP structure (arabinoxylan or pectin) rather, the effect was to a high degree ingredient specific. In pigs fed diet CFO, three TRFs related to Prevotellaceae together consisted of more than 25% of the fecal microbiota, which is about 3 to 23 times higher (P<0.05) than in pigs fed the other diets. Whereas pigs fed diet WB had about 2 to 22 times higher abundance (P<0.05) of Megasphaera elsdenii in feces and about six times higher abundance (P<0.05) of Lactobacillus reuteri in ileal digesta than pigs fed the other diets. The total amount of digested NSP (r=0.57; P=0.002), xylose (r=0.53; P=0.004) and dietary fiber (r=0.60; P=0.001) in ileal digesta were positively correlated with an increased abundance of Bacteroides–Prevotella–Porphyromonas. The effect on SCFA was correlated to specific neutral sugars where xylose increased the ileal butyric acid proportion, whereas arabinose increased the fecal butyric acid proportion. Moreover, chicory pectin increased the acetic acid proportion in both ileal digesta and feces.     

The bacterial and archaeal community structures and methanogenic potential of the cecal microbiota of goats fed with hay and high-grain diets

The cecum plays an important role in the feed fermentation of ruminants. However, information is very limited regarding the cecal microbiota and their methane production. In the present study, the cecal content from twelve local Chinese goats, fed with either a hay diet (0% grain) or a high-grain diet (71.5% grain), were used to investigate the bacterial and archaeal community and their methanogenic potential. Microbial community analysis was determined using high-throughput sequencing of 16S rRNA genes and real-time PCR, and the methanogenesis potential was assessed by in vitro fermentation with ground corn or hay as substrates. Compared with the hay group, the high-grain diet significantly increased the length and weight of the cecum, the proportions of starch and crude protein, the concentrations of volatile fatty acids and ammonia nitrogen, but decreased the pH values (P?<?0.05). The high-grain diet significantly increased the abundances of bacteria and archaea (P?<?0.05) and altered their community. For the bacterial community, the genera Bifidobacterium, Prevotella, and Treponema were significantly increased in the high-grain group (P?<?0.05), while Akkermansia, Oscillospira, and Coprococcus were significantly decreased (P?<?0.05). For the archaeal community, Methanosphaera stadtmanae was significantly increased in the high-grain group (P?<?0.05), while Methanosphaera sp. ISO3-F5 was significantly decreased (P?<?0.05). In the in vitro fermentation with grain as substrate, the cecal microorganisms from the high-grain group produced a significantly higher amount of methane and volatile fatty acids (P?<?0.05), and produced significantly lower amount of lactate (P?<?0.05). Conclusively, high-grain diet led to more fermentable substrates flowing into the hindgut of goats, resulting in an enhancement of microbial fermentation and methane production in the cecum.