3 results
Resistant starch reduces large intestinal pH and promotes fecal lactobacilli and bifidobacteria in pigs
- B. U. Metzler-Zebeli, N. Canibe, L. Montagne, J. Freire, P. Bosi, J. A. M. Prates, S. Tanghe, P. Trevisi
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Dietary resistant starch (RS) may have prebiotic properties but its effects on fermentation and the microbial population are inconsistent. This meta-analysis aimed to quantify the relationship between RS type 2 (RS2) and intestinal short-chain fatty acids (SCFA) and pH as well as certain key bacterial taxa for intestinal health in pigs. From the 24 included articles with sufficient information about the animal, and dietary and physiological measurements published between 2000 and 2017, individual sub-data sets for fermentation metabolites, pH, bacterial abundances and apparent total tract digestibility were built and used to parameterize prediction models on the effect of RS2, accounting for inter- and intra-study variability. In addition, the effect of pig’s BW at the start of the experiment and duration of the experimental period on response variables were also evaluated using backward elimination analysis. Dietary RS levels ranged from 0% to 78.0% RS, with median and mean RS levels of 28.8% and 23.0%, respectively. Negative relationships could be established between dietary RS and pH in the large intestine (P<0.05), with a stronger effect in the mid and distal colon, and feces (R2=0.64 to 0.81; P<0.001). A dietary level of 15% RS would lower the pH in the proximal, mid-, distal colon and feces by 0.2, 0.6, 0.4 and 0.6 units, respectively. Increasing RS levels, however, did not affect SCFA concentrations in the hindgut, but enhanced the molar proportion of propionate in mid-colon and reduced those of acetate in mid-colon and of butyrate in mid- and distal colon (R2=0.46 to 0.52; P<0.05). Backward elimination indicated an age-related decrease in mid-colonic propionate proportion and increase in mid- and distal colonic butyrate proportion (P<0.05), thereby modulating RS2 effects. In feces, increasing RS levels promoted fecal lactobacilli (R2=0.46; P<0.01) and bifidobacteria (R2=0.57; P<0.01), whereby the slope showed the need for a minimal RS level of 10% for a 0.5 log unit-increase in their abundance. Best-fit equations further supported that a longer experimental period increased fecal lactobacilli but decreased fecal bifidobacteria (P<0.05). In conclusion, dietary RS2 seems to effectively decrease digesta pH throughout the large intestine and increase lactic acid-producing bacteria in feces of pigs which may limit the growth of opportunistic pathogens in the hindgut. To achieve these physiologically relevant changes, dietary RS should surpass 10% to 15%.
Restoration of in situ fiber degradation and the role of fibrolytic microbes and ruminal pH in cows fed grain-rich diets transiently or continuously
- P. Pourazad, R. Khiaosa-ard, B. U. Metzler-Zebeli, F. Klevenhusen, Q. Zebeli
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In this study, we used two different grain-rich feeding models (continuous or transient) to determine their effects on in situ fiber degradation and abundances of important rumen fibrolytic microbes in the rumen. The role of the magnitude of ruminal pH drop during grain feeding in the fiber degradation was also determined. The study was performed in eight rumen-fistulated dry cows. They were fed forage-only diet (baseline), and then challenged with a 60% concentrate diet for 4 weeks, either continuously (n=4 cows) or transiently (n=4 cows). The cows of transient feeding had 1 week off concentrate in between. Ruminal degradation of grass silage and fiber-rich hay was determined by the in situ technique, and microbial abundances attached to incubated samples were analyzed by quantitative PCR. The in situ trials were performed at the baseline and in the 1st and the last week of concentrate feeding in the continuous model. The in situ trials were done in cows of the transient model at the baseline and in the 1st week of the re-challenge with concentrate. In situ degradation of NDF and ADF of the forage samples, and microbial abundances were determined at 0, 4, 8, 24 and 48 h of the incubation. Ruminal pH and temperature during the incubation were recorded using indwelling pH sensors. Compared with the respective baseline, both grain-rich feeding models lowered ruminal pH and increased the duration of pH below 5.5 and 5.8. Results of the grass silage incubation showed that in the continuous model the extent of NDF and ADF degradation was lower in the 1st, but not in the last week compared with the baseline. For the transient model, degradation of NDF of the silage was lower during the re-challenge compared with the baseline. Degradation of NDF and ADF of the hay was suppressed by both feeding models compared with the respective baseline. Changes in fiber degradation of either grass silage or hay were not related to the magnitude of ruminal pH depression during grain-rich feeding. In both feeding models total fungal numbers and relative abundance of Butyrivibrio fibrisolvens attached to the incubated forages were decreased by the challenge. Overall, Fibrobacter succinogenes was more sensitive to the grain challenge compared with Ruminococcus albus and Ruminococcus flavefaciens. The study provided evidence for a restored ruminal fiber degradation after prolonged time of grain-rich feeding, however depending on physical and chemical characteristics of forages.
Enzymatically modified starch up-regulates expression of incretins and sodium-coupled monocarboxylate transporter in jejunum of growing pigs
- B. U. Metzler-Zebeli, R. Ertl, D. Grüll, T. Molnar, Q. Zebeli
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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.