In vitro fermentation characteristics, in vivo ileal and total tract nutrient digestibilities, and fecal microbiota responses of dogs to α-cyclodextrin.

The objectives were to examine in vitro fermentation characteristics, in vivo nutrient digestibility, fecal microbiota, and serum lipid profiles as affected by α-cyclodextrin (ACD) supplementation. Short-chain fatty acid (SCFA) production was measured after in vitro fermentation for 3, 6, 9, and 12 h of ACD, ß-cyclodextrin, and γ-cyclodextrin. Five mixed-breed hounds were used in a Latin square design. Each experimental period comprised 14 d, including 10 d for diet adaptation and 4 d for fecal collection. Dogs were fed, twice a day, an extruded diet made with poultry byproduct meal and brewer's rice as the main ingredients. Dogs were supplemented with 0, 1, 2, 3, or 4 g of ACD diluted in 15 mL of water twice daily for a total of 0, 2, 4, 6, and 8 g ACD/d. Maximal in vitro production of total SCFA was lowest for ACD. However, the greatest maximal production of propionate was noted for ACD treatment. Total tract nutrient digestibility and fecal DM concentration linearly decreased ( < 0.05) for treatment groups receiving ACD; no changes were observed for ileal digestibility. Serum cholesterol and triglyceride concentrations were within normal ranges for dogs and were not different among treatments. Similarly, no changes in fecal microbiota were observed. Overall, ACD supplementation appears to have no effect on nutrient absorption in the small intestine but may alter fermentation in the large bowel, which could lead to a higher proportion of propionate production as observed in the in vitro experiment.

Serum lipid profiles, total tract nutrient digestibility, and gastrointestinal tolerance by dogs of α-cyclodextrin.

The objectives were to quantify gastrointestinal tolerance, total tract nutrient digestibility, and serum lipid profiles of dogs as affected by α-cyclodextrin (ACD) supplementation and to validate the accuracy of fat analyses techniques using novel ACD-fat complexes. The ACD was hydrolyzed and free sugars and hydrolyzed monosaccharides were quantified using high performance liquid chromatography. Known amount of fats were complexed with ACD, and fat content of complexes were determined using the ether extraction and acid-hydrolyzed fat methods. Nine mixed-breed hounds were used in a crossover design with 3 periods of 10 d each, including 6 d for diet adaptation and 4 d for fecal collection. Dogs were fed twice daily a diet with poultry byproduct meal and brewer's rice as the main ingredients, and chromic oxide (0.2%) was included as a digestion marker. Dogs were supplemented with either 0, 3, or 6 g of ACD diluted in 15 mL of water twice per day for a total of 0, 6, and 12 g ACD per day. The ACD had a very low free sugar concentration and, once hydrolyzed, released only glucose, as expected. Average daily food intake, fecal output (DM basis), and fecal scores were not significantly different among treatments. Body weight and condition score and serum triglycerides and cholesterol concentrations remained unaltered throughout the duration of the experiment. Dry matter, OM, and fat digestibility coefficients were lower (P < 0.05) for both treatment groups compared to the control. The acid-hydrolyzed fat method was valid to measure fat that was bound to ACD. Intake of ACD lowered fat digestibility somewhat but not to the extent previously reported, without affecting serum lipid concentrations or outcomes related to tolerance. Therefore, ACD supplementation resulted in a small decrease in fat digestibility, but ACD supplementation might have potential in modifying serum lipid profiles.

Effects of a beverage containing an enzymatically induced-viscosity dietary fiber, with or without fructose, on the postprandial glycemic response to a high glycemic index food in humans.

OBJECTIVE: Dietary supplementation with guar gum or fructose has been reported to reduce the postprandial glycemic response to an oral glucose challenge. As a result of the poor palatability of most foods containing guar gum, a novel low-viscosity beverage with guar gum was developed that becomes viscous in vivo through an enzymatic induction. The primary study objective was to determine the effect of an amylase-induced viscosity (I-V) product, with or without supplemental fructose, on the postprandial glycemic response to a high glycemic index test meal in healthy nondiabetic subjects. DESIGN: The study was a four-treatment, placebo-controlled, double-blind, randomized block protocol. SETTING: The study was performed at Glycaemic Index Testing, Inc., Toronto, Ontario, Canada. SUBJECTS: A total of 30 healthy nondiabetic volunteers (13 male, 17 female, mean+/-s.e.m. age of 51+/-3 y and body mass index of 24.2+/-0.4 kg/m(2)) participated in the study. INTERVENTION: In the morning after an overnight fast, subjects participated in four 3-h meal glucose tolerance tests on separate occasions. The test meals contained 50 g of available carbohydrate from maltodextrin and white bread (control) or the same meal with either 5 g of guar gum (3.6 g galactomannan), 5 g of fructose, or 5 g of guar gum +5 g of fructose. RESULTS: Treatments containing guar gum had a reduced (P<0.01) baseline-adjusted peak glucose response and incremental area under the glucose curve. In contrast to previous studies, fructose increased (P<0.05) the baseline-adjusted peak glucose concentration. CONCLUSIONS: Guar gum incorporated into an amylase I-V product provided a means to stabilize blood glucose levels by reducing the early phase excursion and then by appropriately maintaining the later phase excursion in healthy nondiabetic humans.

Glycemic response to a food starch esterified by 1-octenyl succinic anhydride in humans.

To evaluate the glycemic response to a food starch esterified by 1-octenyl succinic anhydride (OSA), 30 healthy nondiabetic adult subjects were studied in a double-blind crossover design. After an overnight fast, subjects consumed a product containing either 25 g of glucose or 25 g of OSA-substituted starch. Finger-prick capillary blood was obtained at baseline and 15, 30, 45, 60, 90, and 120 min postprandial for glucose measurement. After OSA treatment, the rise in blood glucose was reduced (P < 0.05) at 15 and 30 min and tended (P < 0.08) to be lower at 45 min. Mean peak rise in glucose was reduced 19% (P < 0.01) by OSA (3.30 +/- 0.19 versus 2.66 +/- 0.16 mmol/L) compared to glucose, but time to peak did not differ between treatments. Net incremental area under the curve was also lower (P < 0.05) on OSA compared to glucose. Minimal effects on gastrointestinal symptoms (intensity and frequency of nausea, cramping, distention, and flatulence) were noted for both products, with no clinically significant difference between products. In conclusion, starch substitution with OSA attenuated the postprandial glycemic excursion compared to an equivalent glucose challenge and was well tolerated by fasting healthy adult subjects.

Ion chromatographic determination of three fructooligosaccharide oligomers in prepared and preserved foods.

Fructooligosaccharides (FOS) are short-chain sugars that occur naturally and have dietary benefits for humans. They are widely distributed in nature and are a natural part of the human diet. The objective of this study was to determine the concentrations of 1-kestose (GF(2)), nystose (GF(3)), and 1(F)-beta-fructofuranosylnystose (GF(4)) in a variety of common processed and prepared foods. An ion chromatographic method was developed for this purpose in which the sugar concentrations were measured using integrated amperometry. The samples were simply prepared by blending with water and filtering the suspensions through a 10000 Da cutoff centrifugal filter. These samples were then injected into the ion chromatograph, which had been programmed for gradient elution, and the areas of the sugar peaks obtained compared to those of standard sugars on a calibration curve. Selected samples were prepared both with and without standard spikes in order to assess the efficiency of the determination. Of the vegetables investigated, artichokes contained by far the most FOS, followed by onions; bananas contained more FOS than other fruits investigated. The method was shown to be simple, convenient, and relatively fast for the quantitation of FOS in processed and prepared food products.

Glucose-based oligosaccharides exhibit different in vitro fermentation patterns and affect in vivo apparent nutrient digestibility and microbial populations in dogs.

To evaluate the potential of indigestible oligosaccharides (OS) to serve as "dietary fiber-like" ingredients, it is necessary to determine their extent of indigestibility. In vitro fermentation characteristics of two novel OS, alpha-glucooligosaccharides (GOS) and a maltodextrin-like OS (MD), were compared to those of fructooligosaccharides (FOS), gum arabic (GA), guar gum (GG) and guar hydrolysate (GH). Total short-chain fatty acid (SCFA) production (micromol/g dry matter) as a result of MD fermentation was higher initially compared with GA (P<0.01), but GA was more extensively fermented at 24 h (P<0.01). Total SCFA production for GOS was similar to that for FOS, GG, GH and GA. In the second experiment, GOS and MD were added at 6% to an enteral formula control diet (Control) and fed to ileal-cannulated dogs in a 3x3 replicated Latin-square design. Ileal digestibility of glucose was lower (P<0.05) and carbohydrate (CHO) numerically lower (P = 0.08) for both GOS and MD compared with the Control. Total tract digestibility of CHO and glucose was lower only for MD (P<0.01) compared with the Control. Total fecal weights were higher (P<0.01) for both GOS and MD treatments. Fecal concentration of bifidobacteria was numerically increased by GOS and MD supplementation (P = 0.13 and 0.23, respectively). Thus, GOS and MD are indigestible yet fermentable OS, and may act as "dietary fiber-like" ingredients.

Apparent digestibility and glycaemic responses to an experimental induced viscosity dietary fibre incorporated into an enteral formula fed to dogs cannulated in the ileum.

The purpose of this study was to evaluate the apparent digestibility and postprandial glycaemic responses of ileal-cannulated dogs when fed an experimental induced viscosity dietary fibre (IVF) incorporated into a liquid enteral formula. Dietary treatments were: (1) control; (2) Glucerna; (3) Glytrol; (4) IVF; and (5) Jevity. Diets varied in concentrations of crude protein (CP), fat, starch and total dietary fibre (TDF). Dry matter and starch intakes by dogs fed the Glucerna and Glytrol treatments were lower (P<0.05) than for those consuming the other diets. However, daily intakes of CP and fat followed a reverse trend. Digestibility of nutrients at the ileum was high (>80%) for all dietary treatments. Mineral absorption proximal to the ileum and from the total tract was not significantly different among treatments. Mean incremental area under the serum glucose response curves for dogs fed Glytrol, Glucerna, and IVF treatments were lower (P<0.05) than the control treatment. Induced viscosity fibre appears to have no negative effects on nutrient digestion throughout the gastrointestinal tract. Its ability to moderate serum glucose concentrations would make it a potentially good choice for a diabetic liquid formula.

Safety and tolerance of Lactobacillus reuteri supplementation to a population infected with the human immunodeficiency virus.

Probiotic supplementation may provide health benefits, especially for individuals with an underlying disease state that makes them more susceptible to infections. The purpose of this experiment was to evaluate the safety and tolerance of Lactobacillus reuteri ingestion by subjects infected with the human immunodeficiency virus (HIV). Thirty-nine subjects consumed a freeze-dried preparation of L. reuteri or a placebo for 21 days in a double-masked, parallel design experiment. Serum chemistry, haematology, immune profile, urinalysis, physical examination, gastrointestinal tolerance and faecal microbiota data were collected. No clinically significant changes were noted in any of the safety parameters measured. Overall, tolerance was good in both groups. Consumption of L. reuteri tended to increase faecal levels of L. reuteri on days 7, 14 and 21 of treatment feeding (P < 0.06, P < 0.11 and P = 0.05, respectively). However, faecal levels of L. reuteri and total Lactobacillus species were lower than levels previously observed in healthy male adults. Overall, this study documents that L. reuteri may be fed to HIV-positive individuals at 1 x 10(10) colony forming units/day without any clinically significant safety or tolerance problems.

Apparent digestibility of a debranched amylopectin-lipid complex and resistant starch incorporated into enteral formulas fed to ileal-cannulated dogs1.

The purpose of this study was to evaluate apparent digestibility in ileal-cannulated dogs fed enteral diets containing a debranched amylopectin-lipid complex (V-complex) or resistant starch. Six ileal-cannulated dogs were randomized into a replicated 3 x 3 Latin square design for determination of digestibility of three experimental treatments. Dietary treatments were as follows: 1) control; 2) V-complex; and 3) resistant starch. Diets were similar in chemical composition. Apparent digestibility of dry matter (DM), organic matter (OM) and carbohydrate by dogs fed the control diet was higher (P < 0.05) than for dogs consuming the other diets. Mean apparent digestibilities of carbohydrate for the control, V-complex and resistant starch diets were 89, 76 and 43%, respectively. Both DM and carbohydrate digestibility were lower (P < 0.05) for resistant starch compared with V-complex. Fecal dry and wet weights for dogs fed the control diet were lower (P < 0.05) than for those receiving either the resistant starch or V-complex treatments. Dogs fed the V-complex diet produced approximately 90 g less feces per day than dogs fed resistant starch. Dietary incorporation of V-complex to replace traditional carbohydrates may be beneficial for diabetic patients because of the decreased digestibility and subsequent glucose absorption rate. Furthermore, incorporation of resistant starch into enteral formulas may improve gastrointestinal tract health status as a result of increased fecal bulk, potential dilution of toxins in the intestinal lumen and greater production of short-chain fatty acids.

An enteral formula containing fish oil, indigestible oligosaccharides, gum arabic and antioxidants affects plasma and colonic phospholipid fatty acid and prostaglandin profiles in pigs.

Evidence supports a pathogenic role of arachidonic acid-derived inflammatory mediators within the gastrointestinal tract of patients with inflammatory bowel disease. The purpose of this study was to assess the effects of an ulcerative colitis nutritional formula (UCNF) containing oligosaccharides, fish oil, gum arabic and antioxidants on plasma and colonic phospholipid fatty acid and prostaglandin profiles in pigs. Twenty-four growing barrows in two replications were equally randomized among four killing times (d 0, 7, 14 and 21), and one of two diets, a control and the UCNF. Diets contained comparable levels of protein, fat, and nonstructural carbohydrate and met 100% of the energy requirements of the pig. Intake and body weight were recorded daily while blood, urine and tissue samples were collected at time of kill. Within 1 wk of ingestion of the UCNF, the composition of plasma phospholipid fatty acids showed an increase in 20:5(n-3) and 22:6(n-3) (P < 0.0001) and a decrease in 20:4(n-6) and 18:2(n-6) (P < 0.0001). Similar effects were observed for the phospholipids in the colonic and cecal mucosa. Plasma prostaglandin E was unaffected by treatment, whereas thromboxane B2 and 6-keto-prostaglandin F1 alpha levels were significantly decreased after 7 d of UCNF ingestion. Ingestion of the UCNF resulted in a suppression in the synthesis of proinflammatory prostaglandins by cecal and colonic mucosal cells. Levels of colonic and cecal prostaglandin E, 6-keto-prostaglandin F1 alpha and thromboxane B2 were significantly decreased after 7 d of UCNF ingestion. These changes may have been mediated by rapid increases of (n-3) fatty acids into cellular phospholipids. Dietary supplementation with the UCNF may prove beneficial for patients with ulcerative colitis by modulating colonic prostaglandin synthesis.

Metabolic characteristics of healthy adult males as affected by ingestion of a liquid nutritional formula containing fish oil, oligosaccharides, gum arabic and antioxidant vitamins.

n-3 Fatty acids from fish oil and short-chain fatty acids produced from fermentation of oligosaccharides may attenuate a portion of gut injury and inflammation associated with ulcerative colitis. The purpose of this study was to assess the effects of an enteral nutritional formula containing supplemental oligosaccharides, gum arabic and fish oil on serum metabolite profiles, haematology, plasma and red blood cell membrane phospholipid fatty acid profiles, urinary constituent, and safety in healthy human adult males. 30 subjects were randomly assigned to one of two treatments, a control formula (n = 10) and an ulcerative colitis nutritional formula (UCNF; n = 20). Formulas contained comparable levels of protein, fat and non-structural carbohydrates. Daily intake of the formulas provided nutrients to meet or exceed the recommended daily allowance. Intake was recorded daily while blood and urine samples were collected weekly on days 0, 7 and 14. Certain subjects consuming large quantities of the UCNF experienced some abdominal distention, gas and loose stools. Sole source intake of the UCNF was safe over 14 days as assessed by routine measurements of serum metabolite profiles, haematology and urinalysis compared with subjects fed the control formula. Substantial decreases in plasma and red blood cell phospholipid 18:2n-6 and increases in 20:5n-3 and 22:6n-3 within 1 wk of feeding the UCNF were noted.

Sulfasalazine or enteral diets containing fish oil or oligosaccharides attenuate chronic colitis in rats.

: Recent studies have suggested that n-3 fatty acids from fish oil (FO) as well as short-chain fatty acids may attenuate some of the gut injury and inflammationassociated ulcerative colitic (UC). The objectives of this study were to (a) assess the antiinflammatory activity of sulfasalazine (SAZ), a drug known to be effective in the treatment of human UC in a model of chronic granulomatous colitis in rats and (b) determine whether enteral diets supplemented with either FO or two indigestible oligosaccharides (fructooligosaccharide, FOS; xylooligosaccharide, XOS) could attenuate the inflammation observed in a model of chronic granulomatous colitis. In one series of experiments, female Lewis rats were randomized into three groups consisting of a sham-operated control group, a colitic group, and a colitic group in which rats were given oral sulfasalazine (SAZ) immediately after induction of colitis and continued for 3 weeks. Chronic granulomatous colitis with liver and spleen inflammation was induced by subserosal (intramural) injection of purified peptidoglycan-polysaccharide (PG/PS) into the distal colon. Sham-operated rats were injected with human serum albumin. All rats received standard lab chow. In a second series of experiments, female Lewis rats were randomized into six groups consisting of four colitic groups fed enteral diets, a colitic group fed chow, and a sham-operated group fed a control enteral diet. Enteral diets (300 kcal/kg/day) contained either FO, FOS/ gum arabic, XOS/gum arabic, or no bioactive ingredient (control diet). All rats were fed for 1 week before induction of colitis. Rats consumed the diets for 3 additional weeks before being killed. SAZ significantly attenuated the PG/PS-induced increases in myeloperoxidase (MPO) activity as well as significantly reduced the PG/PS-induced increases in liver and spleen weights. Control (enteral diet) as well as the FO and XOS diets significantly attenuated the increase in colon weight when compared with chow-fed rats. We also found that the FO and XOS diets significantly attenuated the PG/PS-induced increases in colonic MPO activity and colon weight. The FOS and XOS diets significantly attenuated the PG/PS-induced increases in liver weights when compared with PG/PS + chow-fed animals. The antiinflammatory activity of these diets was confirmed by means of histological inspection showing an inhibition of inflammation and maintenance of crypt cell integrity. These results demonstrate that a complete enteral diet supplemented with either FO, FOS, or XOS exhibited antiinflammatory activity that was similar in efficacy to the known antiinflammatory drug SAZ in this model of colitis.

Alteration of the fiber and lipid components of a defined-formula diet: effects on stool characteristics, nutrient digestibility, mineral balance, and energy metabolism in humans.

Eighteen healthy males with a body weight of 70.0 +/- 3.1 kg consumed three defined-formula diets that varied only in their fiber and/or lipid components: 1) 6.4% fiber (100% soy polysaccharides) and 13.1% lipid [50% medium-chain triacylglycerols (MCTs), 40% corn oil, and 10% soy oil]; 2) 3.4% fiber (75% oat fiber, 17.5% gum arabic, and 7.5% carboxymethylcellulose) and 15.6% lipid (20% MCTs, 50% canola oil, and 30% high oleic acid safflower oil); and 3) 4.4% fiber (same as diet 2) and 14.5% lipid (same as diet 1). Consumption of diet 2 resulted in slightly firmer stools and provided the greatest amount of fecal output per unit fiber intake. Total dietary fiber (TDF) digestibility was lowest for men fed diets 2 and 3, but nitrogen and lipid digestibilities and energy metabolism criteria were not different among diets. Although mineral excretion patterns differed among treatments, fiber and lipid components of the diets appeared not to be responsible for these differences. Results indicate that fecal output can be maintained with a lower intake of a blend of oat fiber, gum arabic, and carboxymethylcellulose compared with soy polysaccharides. Except for TDF digestibility, alteration of amounts and/or sources of fiber and lipid components of defined-formula diets used in this experiment did not alter nutrient digestibility, energy metabolism, or mineral retention.

Effects of dietary supplementation with fructooligosaccharides on colonic microbiota populations and epithelial cell proliferation in neonatal pigs.

Two experiments were conducted with neonatal pigs to determine the effects of feeding fructooligosaccharides on cecal and colonic microbiota, proliferation of cecal and colonic epithelial mucosa, and short-chain fatty acid concentrations in the cecum. Experiment 1 consisted of feeding neonatal pigs diets containing either 0 or 3 g fructooligosaccharies/L of formula for 15 days and then examining the large intestine for changes in cecal and proximal colonic microbiota; cecal pH; short-chain fatty acid concentrations; morphology of cecal, proximal, and distal colonic epithelial mucosa; gross necropsy; and histopathology. Supplementation with fructooligosacchariudes (FOS) did not alter cell counts of viable bifidobacterial organisms or total anaerobic microbiota, cecal pH, or concentrations of short-chain fatty acids. Cecal mucosal cell density and labeled cells increased with FOS consumption. Proximal colonic mucosal crypt height, leading edge, labeled cells, proliferation zone, and labeling index increased with FOS consumption. Distal colonic mucosal crypt height, leading edge, cell density, labeling index, and labeled cells increased with FOS consumption. Gross necropsy and histopathology found no significan lesions. In Experiment 2, neonatal pigs were fed diets containing either 0 or 3 g fructooligosaccharides/L of formula for 6 days. Fecal samples were collected on the first full day of feeding and on days 3 and 6 after initiation of feeding. On days 1 and 3, concentrations of bifidobacteria were similar between diets; however, on day 6, pigs consuming FOS tended to have greater numbers of bifidobacteria (p = 0.08). These data suggest dietary consumption of FOS will enhance bifidobacteria populations and prevent colonic epithelial mucosa atrophy in neonates fed an elemental diet.

Dietary fructooligosaccharide, xylooligosaccharide and gum arabic have variable effects on cecal and colonic microbiota and epithelial cell proliferation in mice and rats.

Two experiments were conducted to determine if supplementing soluble fiber (fructooligosaccharide, xylooligosaccharide or gum arabic) to a semi-elemental diet would beneficially change cecal and colonic microbiota populations and enhance epithelial cell proliferation. Experiments 1 and 2 used identical dietary regimens; mice and rats were given free access to a powdered semi-elemental diet. Animals were assigned to one of the four following treatment groups: control, no supplemental dietary fiber, fructooligosaccharide, xylooligosaccharide and gum arabic. Dietary fiber was supplied via drinking water at 30 g/L. In Experiment 1 populations of Bifidobacteria and total anaerobic flora were enumerated from the contents of the cecum and colon of weanling mice. Consumption of fructooligosaccharide increased (P < 0.05) the concentrations of Bifidobacteria and the ratio of Bifidobacteria to total anaerobic flora. In Experiment 2 tissue from the cecum and distal colon of weanling rats was examined for morphological changes of the mucosa. Consumption of xylooligosaccharide increased (P < 0.05) cecal crypt depth and labeling index relative to the other three treatments. Consumption of gum arabic and the control diet increased (P < 0.01) cecal proliferation zone. Consumption of xylooligosaccharide and the control diet increased (P < 0.01) cecal cell density (number of cells in a vertical-half of the crypt). Distal colonic crypt depth was greatest (P < 0.05) in controls and rats fed fructooligosaccharide, intermediate in those fed gum arabic, and smallest in those fed xylooligosaccharide. These results suggest that fructooligosaccharide effectively stimulates growth of Bifidobacteria and xylooligosaccharide supports a modest enhancement of cecal epithelial cell proliferation.

Effect of fiber source on short-chain fatty acid production and on the growth and toxin production by Clostridium difficile.

BACKGROUND: Fermentable fiber promotes the growth of resident gut microbes, which modify the environment of the gastrointestinal tract and thus prevent colonization by Clostridium difficile. METHODS: An in vitro system with pigs as fecal inoculum donors was used to estimate fiber fermentability and changes in intestinal microbiota. RESULTS: Acetate and propionate production (mumol/mg substrate fermented/day) was greatest for gum arabic (1013.4 and 704.1, respectively); butyrate production was greatest for xylo-oligosaccharide (345.6). Growth of total anaerobes and clostridia was greatest for gum arabic (21.2 and 16.2 x 10(8) counts/ml, respectively) and xylo-oligosaccharides (21.0 and 19.6 x 10(8) respectively); growth of acidogenic bacteria was greatest with fructo-oligosaccharide (6.7 x 10(8) counts/ml). No culturable counts of C. difficile were obtained, nor was toxin A detected. CONCLUSIONS: Fermentable fibers support the growth of indigenous intestinal bacteria, particularly acidogenic bacteria, and yield large amounts of short-chain fatty acids with decreased gut pH. These factors contribute to the prevention of growth and toxin elaboration by C. difficile.

The effect of fiber source in enteral products on fecal weight, mineral balance, and growth rate in rats.

The effect of two fiber systems in enteral formulas on fecal output, mineral balance, weight gain, and cecal short-chain fatty acid production was studied in rats. Enteral products tested had either no fiber; soy fiber (3.4 g of total dietary fiber/8 fluid oz); a fiber blend containing 75% oat fiber, 17.5% gum arabic, and 7.5% carboxymethylcellulose (3.4 g of total dietary fiber/8 fluid oz); or the same blend at 4 g of total dietary fiber/8 fluid oz. Food, feces, and urine were analyzed for nitrogen, calcium, magnesium, iron, and zinc. Cecal contents were analyzed for short-chain fatty acids. Weight gain, intake, food efficiency, and nitrogen balance were unaffected by fiber source. Fecal weight was increased by the fiber blend (p < .05). Calcium and magnesium balances were similar for all groups fed fiber-containing products but were lower for the fiber-free group (p < .05). Iron balance was significantly lower for rats fed the fiber blend at 4 g/8 fluid oz as compared with the other treatment groups (p < .05). Cecal acetate, propionate, and total short-chain fatty acid concentrations for rats fed the soy-fiber diet were significantly higher than for the other three diets (p < .05). Rats fed the fiber blend at the higher level had a significantly higher percentage of butyrate production than rats fed the other three diets (p < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary nitrogen and lipid utilization by growing pigs fed structured triacylglycerides synthesized from medium-chain triacylglycerides and menhaden oil.

A total of 24 crossbred barrows were used in a 19-d metabolism trial to determine the effect of dietary structured triacylglycerides synthesized by the random reesterification of medium-chain triacylglycerides (MCT) and menhaden oil on growth performance, nitrogen retention, and apparent digestibilities of nitrogen, lipid, and fatty acids. Pigs were randomly assigned to four dietary treatments differing only in lipid source. Dietary treatments (percentage by weight of total lipid) contained either 1) corn oil: soybean oil:MCT oil (40:10:50), 2) MCT oil:menhaden oil (60:40 as structured triacylglyceride), 3) MCT oil: menhaden oil (60:40 nonstructured, physical mixture), or 4) structured triacylglyceride (as in 2): safflower oil:canola oil (80:10:10). Total fecal and urine collections were conducted during two 5-d periods. Apparent nitrogen digestibility and nitrogen retention were high (> 95%) and not affected (P > .05) by dietary treatment. Apparent fatty acid digestibilities were affected by dietary lipid source. Palmitic and arachidonic acid digestibilities were lower (P < .05) for Diet 1, heptadecanoic acid digestibility was elevated by 21% (P < .05) for Diet 2 relative to Diet 3, and stearic acid digestibility was highest (P < .05) for Diet 1, followed by Diets 2, 3, and 4 in decreasing order. This study demonstrates that the physical nature of the lipid (structured vs nonstructured) affects fatty acid digestibility patterns in the growing pig. Further evaluation of MCT/menhaden oil structured triacylglyceride is needed.

Fermentation of dietary fibre by human colonic bacteria: disappearance of, short-chain fatty acid production from, and potential water-holding capacity of, various substrates.

Several dietary fibre-rich substrates were fermented in vitro with human colonic bacteria obtained from each of three adult male subjects to assess the extent of substrate fermentation short-chain fatty acid (SCFA) production, and the potential effect of fermented residues on faecal bulk. Substrates tested were two varieties of oat hull fibre, gum arabic, carboxymethylcellulose (CMC), soy fibre, psyllium, and six blends containing oat fibre, gum arabic, and CMC in various proportions. All substrates contained greater than 900 g/kg of total dietary fibre except for CMC (816 g) and soy fibre (778 g). In vitro organic matter disappearance during fermentation was greatest for gum arabic (69.5%), intermediate for soy fibre (56.4%), and less than 20% for the two oat fibres, CMC, and psyllium. Averaged across substrates, acetate, propionate, and butyrate were produced in the molar proportion of 64:24:12. Potential water-holding capacity (PWHC) of substrates, a measure of faecal bulking potential, was greatest for CMC (13.5 g H2O/g substrate) and lowest for gum arabic (1.92 g) and soy fibre (1.71 g). Organic matter disappearance and SCFA production of blends were directly proportional to their gum arabic content. Blend PWHC was proportional to CMC content. In vitro procedures are useful in predicting the actions of fibre blends formulated to produce desirable effects in vivo.

Short-chain fatty acid production and fiber degradation by human colonic bacteria: effects of substrate and cell wall fractionation procedures.

Three dietary fiber sources (corn fiber, oat bran, wheat bran) were analyzed for chemical composition and potential fermentation by human colonic bacteria in vitro. Total dietary fiber (TDF) concentration of substrates was 64.3, 11.1 and 50.4 g/100 g dry matter for corn fiber, oat bran and wheat bran, respectively. Original material (ORIG), TDF fractions and simulated (SIM) cell wall fractions (produced by combining cellulose, hemicelluloses and pectic substances in proportions they represented in the cell wall) from each substrate were fermented in vitro for 6, 12, 18, 24 or 48 h using inoculum prepared from freshly voided feces from each of three human volunteers. Substrate dry matter remaining after 48 h of fermentation was 87.8, 39.8 and 73.5% for TDF fractions of corn fiber, oat bran and wheat bran, respectively. Disappearance of ORIG fractions was considerably greater than that of TDF due to fermentation of nonfibrous material. Disruption of cell wall structure during isolation of polysaccharide fractions allowed for dramatically increased fermentability of SIM relative to TDF. Averaged across all treatments, production of the short-chain fatty acids, acetate, propionate and butyrate, occurred in the molar ratio 63:21:16; however, profiles of short-chain fatty acids produced were influenced by both treatment and inoculum source. Extent of substrate fermentation varied among inoculum donors, implying that colonic microbial activities differ among individuals. Potential colonic fermentability of fiber sources was influenced by substrate, method of fiber preparation and inoculum source.