Fecal Neutral Detergent Fiber Research Articles

Faecal index to estimate intake and digestibility in grazing sheep

SUMMARYThe current research was carried out to evaluate the use of crude protein and fibre components in faeces for estimating intake and digestibility in sheep fed with pearl millet (Pennisetum americanum (L.) Leeke). The equations were developed from four trials in metabolism cages with 16 sheep in each trial. Each animal received a different quantity of millet leaves in the diet: 0·015, 0·020 and 0·025 dry matter (DM) as a proportion of live weight (LW) and ad libitum with at least 0·2 of daily feed refusals. Organic matter intake (OMI, g/day) was measured, through the difference between offer and refusals; total faeces were collected for 5 days, which was used to determine faecal crude protein (CPf, g/day and g/kg of organic matter (OM)), faecal neutral detergent fibre (NDFf, g/day and g/kg OM), faecal acid detergent fibre (ADFf, g/day and g/kg OM) and OM digestibility (OMD). Linear regression equations were calculated to determine the relationship between OMI and CPf (P<0·001, R2=0·90, relative prediction error (RPE=14·02%). A multiple linear equation was generated for OMI including CPf and NDFf (P<0·001, R2=0·94; RPE=9·25%). Hyperbolic (single and multiple) and exponential models were tested to estimate OMD, where the hyperbolic multiple model including CPf and NDFf showed lower RPE (3·90%). These equations for estimating OMI and OMD were evaluated on sheep grazing P. americanum fertilized with increasing levels of nitrogen (N) (50, 100, 200 and 400 kg N/ha), comparing measured and estimated OMI. The intake estimated by multiple regression (CP and NDFf) showed a higher R2 (0·98) and lower RPE (5·25%) than the simple (CPf only) linear equation (R2=0·94; RPE=20·45%). The results demonstrated the feasibility of using the faecal index generated in metabolism cages for estimating intake and digestibility in sheep grazing P. americanum.

Fibre digestibility in large herbivores as related to digestion type and body mass — An in vitro approach

The coexistence of different ungulate species in a given ecosystem has been the focus of many studies. Differences between ruminant foregut fermenters and hindgut fermenters were remarkable for example in the way they ingest and digest high fibre diets. Digestion trials based on total collections are difficult to conduct or are sometimes even not possible for wild animals in the field or in zoos. To gain information on the fibre digestion achieved by these animals and the influence of body mass (BM) thereon, a method using spot sampling is desirable. In this study, in vitro fermentation of faecal neutral detergent fibre (NDF) was used as a measure of fibre digestion in large ungulates. Food and faecal samples of 10 ruminant foregut fermenting and 7 hindgut fermenting species/breeds were collected. All animals received 100% grass hay with ad libitum access. The NDF of food and faeces was fermented in vitro in a Hohenheim gas test (HGT) for 96h. The digestion type generally had an effect on the gas production (GP) of faecal NDF in the HGT with hindgut fermenters showing higher values than ruminant foregut fermenters. At any time interval of incubation, BM had no influence on GP. The results are in accordance with both findings that ruminant foregut fermenters have longer mean retention times and more comprehensive particle reduction and findings of a lack of influence of BM on digesta mean retention time. It can be stated that the HGT (96h) is a useful and quick method to show also small differences within groups in fibre digestion.

Effect of varying total mixed ration particle size on rumen digesta and fecal particle size and digestibility in lactating dairy cows

The objective of this experiment was to evaluate the effects of feeding rations of different particle sizes on rumen digesta and fecal matter particle size. Four rumen-cannulated, multiparous, Holstein cows (104±15 d in milk) were randomly assigned to treatments in a 4×4 Latin square design. The diets consisted of 29.4% corn silage, 22.9% ground corn, 17.6% alfalfa haylage, and 11.8% dry grass hay [20% of forage dry matter (DM)] on a DM basis. Dry grass hay was chopped to 4 different lengths to vary the total mixed ration (TMR) particle size. Geometric mean particle sizes of the rations were 4.46, 5.10, 5.32, and 5.84mm for short, medium, long, and extra long diets, respectively. The ration affected rumen digesta particle size for particles ≥3.35mm, and had no effect on distribution of particles <3.35mm. All rumen digesta particle size fractions varied by time after feeding, with soluble particle fractions increasing immediately after feeding and 0.15, 0.6, and 1.18-mm particle size fractions decreasing slightly after feeding. Particle fractions >1.18mmhad ration by time interactions. Fecal neutral detergent fiber (NDF) and indigestible NDF concentrations decreased with increasing TMR particle size. Fecal particle size expressed as total geometric mean particle length followed this same tendency. Fecal particle size, expressed as retained geometric mean particle length, averaged 1.13mm with more than 36% of particles being larger than 1.18mm. All fecal nutrient concentrations measured were significantly affected by time after feeding, with NDF and indigestible NDF increasing after feeding and peaking at about 12h later and then decreasing to preprandial levels. Starch concentrations were determined to have the opposite effect. Additionally, apparent digestibility of diet nutrients was analyzed and DM digestibility tended to decrease with increasing TMR particle size, whereas other nutrient digestibilities were not different among rations. These results show that the critical size for increased resistance to rumen escape is larger than 1.18mm and this critical size is constant throughout the day. This study also concludes that, when using average quality grass hay to provide the range of particle sizes fed, DM digestibility tends to decrease with increasing ration particle size.

Comparative investigations on digestion in grazing (Ceratotherium simum) and browsing (Diceros bicornis) rhinoceroses

Rhinoceroses represent the largest extant herbivores with extensive dietary specialization for plant groups like browse (black rhino Diceros bicornis) or grass (white rhino Ceratotherium simum). However, it is not clear to what extent such diet selection patterns are reflected in adaptations of digestive physiology of the respective feeding types. In this study, feeding trials with four black and five white rhinos were conducted in four zoos. The animals had ad libitum access to the same batch of grass hay (second cut; neutral detergent fiber (NDF) 63% dry matter (DM), crude protein 10.2% DM). Total intake, fecal N content, in vitro digestibility of NDF residues of feces, fecal particle size and mean retention time (MRT) of particles (Cr-mordanted fiber; 1–2mm) and fluid (Co-EDTA) were quantified. The average daily DM intake was 70±12g/kg BW0.75 for white and 73±10g/kg BW0.75 for black rhinos. In the in vitro fermentation test fecal NDF residues of black rhinos resulted in higher gas productions at fermentation times of 12 to 24h, indicating that white rhinos have a superior capacity to digest NDF. Average MRT for fluids and particles was 28±4h and 43±5h in white and 34±4h and 39±4h in black rhinos. The selectivity factor (SF=MRTparticle/MRTfluid) was higher for white (1.5±0.2) than for black rhinos (1.2±0.1) (p=0.016). In a comparison of 12 ruminant and 3 rhino species, SF was correlated to percentage of grass in diet (R=0.75). Mean fecal particle size was higher in white (9.1±1.94mm) than in black rhinos (6.1±0.79mm) (p=0.016). The results demonstrate differences between white and black rhinos in terms of retention times and fiber digestibility. The more selective retention of particles by the white rhino corresponds with the higher digestion of fiber measured indirectly. Furthermore there is indication for a general pattern of high SF in grazing ruminants and rhinos. The difference in fecal particle size between both rhino species might be due to the considerable difference in body weight.

A meta-analysis of feed digestion in dairy cows. 2. The effects of feeding level and diet composition on digestibility

A meta-analysis based on published experiments with lactating dairy cows fed mainly grass silage-based diets was conducted to study the effects of intake, diet composition, and digestibility at a maintenance level of feeding on the apparent total diet digestibility. A data set that included a total of 497 dietary treatment means from 92 studies was collected and analyzed using mixed model regression analysis with a random study effect. Diet organic matter digestibility (OMD) in dairy cows at a production level (OMDp) was positively associated with OMD at maintenance (OMDm), but the slope was less than 1 (0.69). Diet OMDp decreased as feed intake increased, and diets with high OMDm exhibited greater depressions in digestibility with increased intake than did diets with low OMDm. Digestibility of organic matter and neutral detergent fiber (NDF) increased as dietary crude protein concentration increased, whereas increased concentrate fat decreased digestibility. Replacement of grass silage with whole-crop cereal silage was associated with a quadratic decrease in diet digestibility. Metabolic fecal output, defined as fecal organic matter minus NDF, averaged 95.8 (SE=0.65) g/kg of dry matter intake, and it was not influenced by intake or diet composition. Variation in OMDp in cows fed grass silage-based diets was therefore attributable to variation in dietary NDF concentration and NDF digestibility. Depression in digestibility of organic matter with increased intake was less than predicted by the National Research Council and Cornell Net Carbohydrate and Protein systems. The following 2-parameter model indicates that the difference between OMD estimated in sheep fed at maintenance compared with dairy cows at production level is related both to dry matter intake and digestibility at maintenance level: OMDp=257 (±43) + 0.685 (±0.054) × OMDm (g/kg of dry matter) – 2.6 (±0.44) × dry matter intake (kg/d); adjusted residual mean square error=8.4g/kg. It was concluded that diet digestibility in dairy cows can be predicted accurately and precisely from digestibility estimated at maintenance intake in sheep by using regression models including animal and dietary factors.

Cellulase Supplementation Does Not Improve the Digestibility of a High-Forage Diet in Horses

Abstract Six mature Arabian geldings were used in a two-period crossover study to investigate the effects of cellulase supplementation on fiber digestion. Horses were randomly assigned to either a control (CO; n = 3) or a cellulase (CE; n = 3) treatment for the first period and then treatments were switched for period 2. Each period consisted of a 10-day diet adaptation followed by a 3-day total fecal collection. The enzyme mixture contained 40,000 cellulase units/g and was fed at a rate of 3 g/day split evenly between two feedings. During the diet adaptation period, horses had ad libitum access to timothy hay and were also fed 165 g whole oats as a carrier for the supplement. When eating the CO treatment, horses consumed 16% more hay than when on the CE treatment (P = .004). Fecal output also tended to be greater when horses consumed the CO treatment as compared with CE treatment (P = .07). No differences were found between treatments for fecal percent dry matter (DM%), fecal neutral detergent fiber (NDF), fecal acid detergent fiber (ADF), fecal nitrogen (N), or fecal gross energy (GE). There was a trend for horses consuming the CO treatment to digest more NDF than when consuming the CE treatment (34.6% ± 1.5 vs 31% ± 1.5; P = .07). Horses also digested a greater %ADF, %N, and Mcal of energy when consuming the CO treatment than when consuming the CE treatment (P

The effect of enzyme treatment of soybean meal on oligosaccharide disappearance and chick growth performance

Research was conducted to determine the effects of enzymatically hydrolyzing raffinose and stachyose from soybean meal (SBM) on fecal oligosaccharide concentration and growth performance of chicks fed a corn-SBM diet. The alpha-galactosidase treatment was optimized for oligosaccharide degradation. Enzyme treatment degraded raffinose and stachyose in SBM by 69 and 54%, respectively, compared to untreated soybean meal (USBM). Diets containing enzyme-treated soybean meal (ESBM) resulted in excreta raffinose and stachyose concentrations reduced to below measurable levels (<0.1 mg/ g feces). Enzyme treatment increased (P < 0.05) TME from 2,974 to 3,328 kcal/kg. Three chick growth studies were conducted to determine the effect of feeding ESBM on growth performance. There were no statistical differences (P > 0.05) in growth performance among treatments. Chicks fed the ESBM diet had an increased (P < 0.05) fecal neutral detergent fiber (NDF) content in one of two studies. A fourth experiment was conducted to determine if heating, used to enhance enzyme treatment, would decrease lysine availability. Heating significantly (P < 0.05) reduced lysine availability compared to USBM. These experiments demonstrated that feces could be made void of raffinose and stachyose, but chick growth performance was not significantly (P > 0.05) improved by enzyme treatment.

Nitrogen and fiber concentration in rumen contents and feces contents of Mongolian gazelles

Fecal indicators of nutritional status of wild ungulates were less constrained than that of blood, rumen contents, or urine analyses. Thus, we compared the nitrogen and fiber concentrations of feces with those of the rumen contents of Mongolian gazelles (Procapra guttrurosa) in Hulunbeier Grassland. Rumen contents and fecal nutritional concentrations varied in different seasons. Dietary nitrogen concentrations only increased linearly with increase nitrogen concentration in fecal in winter. There was a positive correlation between rumen NDF (neutral detergent fiber) and fecal NDF concentrations. But the regression coefficient was small (r=0.3917). There was a significant regression equation between rumen contents ADF (acid detergent fiber) and fecal ADF concentrations, as well as ADL (acid detergent lignin) concentrations. Nitrogen concentration was found to be negatively correlated with NDF, ADF, and ADL concentrations both in rumen and in fecal compositions. Our data suggest that fecal nitrogen, ADF, ADL concentrations may assess winter dietary qualities that are in protein, crude fiber and lignin concentrations for Mongolian gazelles.

Relationships Among Splanchnic Tissue Energy Consumption and Net Flux of Nutrients, Feed Intake and Digestibility in Wethers Consuming Forage-Based Diets ad libitum

Goetsch, A.L. and Patil, A.R. 1997. Relationships among splanchnic tissue energy consumption and net flux of nutrients, feed intake and digestibility in wethers consuming forage-based diets ad libitum. J. Appl. Anim. Res., 11: 1–18. Data from crossbred catheterized wethers (38±0.6 kg body weight) consuming forage-based diets ad libitum in eleven experiments were used to determine relationships among splanchnic tissue energy consumption and net flux of nutrients, feed intake and digestibility. Portal-drained viscera (PDV) and hepatic energy consumption increased linearly as digestible energy intake (DEI) increased (PDV energy consumption, Mcal/d = 0.2005 + 0.0660 [DEI, Mcal/d], R2 = 22%; hepatic energy consumption, Mcal/d = 0.1457 + 0.0659 [DEI, Mcal/d], R2 = 25%). However, improvements in R2 occurred when other independent variables were included in regressions (PDV energy consumption, Mcal/d = −0.0112 + 0.1859 [DEI, Mcal/d]—0.0254 [DEI2, Mcal/d] + [fecal neutral detergent fiber, kg/d], R2 = 34%; hepatic energy consumption = 0.0014 + 0.0266 [DEI, Mcal/d] + 0.3325 [PDV energy consumption, Mcal/d] + 0.0745 [hepatic urea nitrogen net flux, M/d] + 0.0016 [body weight, kg], R2 = 48%). Splanchnic bed energy consumption as a percentage of DEI was best described (R2 = 49%) by 43.611–9.531 [DEI, Mcal/d] + 15.914 [fecal neutral detergent fiber, kg/d] + 6.057 [hepatic urea nitrogen net flux, M/d]. A regression of hepatic urea nitrogen net flux on hepatic net fluxes of alpha-amino and ammonia nitrogen accounted for 25% of variation, of which 55 and 45% was attributable to alpha-amino and ammonia nitrogen, respectively. In conclusion, factors besides physiological workload as depicted by DEI accounted for variability in energy consumed by splanchnic tissues with ad libitum ingestion of forage-based diets. The decreasing proportion of DEI attributable to splanchnic bed use may contribute to change in animal performance with increasing DEI.

Monitoring Mule Deer Diet Quality and Intake with Fecal Indices

Few studies have evaluated fecal indices for monitoring diet quality and intake of North American deer. We conducted 11 digestion trials with black-tailed (Odocoileus hemionus columbianus Richardson) and mule deer (O. h. hemionus Rafinesque) to examine relationships between several chemical constituents of deer feces (i.e., fecal nitrogen, fecal 2,6-diaminopimelic acid (DAPA), fecal neutral detergent fiber (NDF), fecal acid detergent fiber, and fecal acid detergent lignin) and dry matter intake, digestible energy, digestible energy intake, diet crude protein content, crude protein digestibility, and digestible crude protein intake. We developed regression equations to predict diet quality and intake and also evaluated 2 alternative methods (organic matter basis and neutral detergent fiber (ndf) basis) for quantifying fecal indices. Concentrations of DAPA, fecal NDF, and fecal N were the most precise for estimating diet quality and intake. Extracts from 5 of 11 diets precipitated only small amounts of protein and influence of tannins on protein digestion probably was slight. Quantifying fecal indices per unit organic matter and neutral detergent fiber in the feces was comparable to the standard dry matter basis and under some field conditions should improve their predictive ability. We believe our best equations are suitable for management purposes where diets are similar and intake and quality are believed to be within the ranges we documented.

Intake and digestibility for sheep and goats consuming supplementary Acacia brevispica and Sesbania sesban

The effect of two East African browses, A. brevispica and S. sesban, on feed digestibility and palatability were described. The browses were fed at three levels of each in combination with vetch ( Vicia dasycarpa) and teff straw ( Eragrostis abyssinica) in a Latin Square design to sheep and goats. Teff straw had low nitrogen (N) content (0.6%), high fiber (neutral-detergent fiber (NDF) = 72%), but low lignin (5.3%) and high true digestibility (73%). A. brevispica and vetch had similar amounts of NDF (43 and 37%) but A. brevispica had twice as much lignin, therefore lower true digestibility. A. brevispica also contained proanthocyanidins, which were absent in other feeds. S. sesban had low fiber (NDF = 21%), low lignin (3%) and high true digestibility (90%). Sheep had lower refusals of browse and higher intake rates than goats. Sheep refused only diets containing A. brevispica, perhaps because of its proanthocyanidin content. Both A. brevispica and vetch hay had reduced palatability for goats, making it impossible to separate the effect of tannins from that of fiber. Although it has been suggested that tannins reduce the digestibility of feed by inhibiting rumen microbes, there seemed to be no such effect in this case because the microbial and endogenous fraction of feces (MI), was constant across diets. There was less fecal metabolic N in diets containing S. sesban, as measured by the N concentration of neutral-detergent solubles of feces, which may be best explained by the higher fiber content of A. brevispica and vetch rather than by tannins. Tannins in A. brevispica did seem to complex with feed protein as indicated by higher concentration of N in fecal NDF (NDF-N). These complexes were recovered as fecal lignin causing a large discrepancy between true and predicted digestibility and lower N digestibility.

Net flux of nutrients across splanchnic tissues in sheep fed tropical vs. temperate grass hay of moderate or low qualities

Abstract Crossbred wethers (18 months old; 44 ± 0.7 kg body weight), with catheters in a hepatic vein, the portal vein and a mesenteric vein and artery, consumed ad libitum tropical or temperate grass hay each of three different qualities or stages of maturity. Splanchnic tissue energy consumption was similar among tropical grass diets but increased as quality of temperate grass declined. Portal-drained viscera oxygen consumption increased with increasing digestible energy intake and fecal neutral detergent fiber excretion. Energy available to extra-splanchnic tissues with highest quality grass was greater for temperate than for tropical grass because of lower splanchnic tissue energy consumption relative to digestible energy intake. Grass source, quality and nitrogen concentration did not significantly affect portal-drained viscera release of α-amino nitrogen. Hepatic uptake of α-amino nitrogen was greater for tropical than for temperate grass, presumably because of higher nitrogen concentration with greater hepatic ammonia nitrogen uptake. Glucose uptake by the portal-drained viscera was greater for tropical than for temperate grass, and the potential contribution of propionate to hepatic glucose release tended to be greatest for grass highest in quality. Grass quality appears more important to achieve maximal energy availability to extra-splanchnic tissues with temperate than tropical grass.

Effect of Exposure on Nitrogen and Fiber Characteristics of White-Tailed Deer Feces

We collected feces from a captive herd of white-tailed deer (Odocoileus virginianus) to determine the effect of time of exposure under laboratory conditions on fecal nitrogen (FN) concentration and the effect of time of exposure under natural conditions on FN and fiber characteristics of feces. No differences were found in FN when pellet groups were exposed to laboratory conditions for 512 days (P = 0.99). The FN concentration also did not differ in pellet groups that were exposed to natural conditions (except when sheltered from rainfall greater than about 1 cm) in Oklahoma for <24 days (P = 0.94) during September and October. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) of pellet groups placed under these conditions also remained similar with different times of exposure (NDF, P = 0.30; ADF, P = 0.90). These results suggest that feces collected 524 days postdefecation can be used to estimate FN, fecal NDF, and fecal ADF.

Effect of corn fiber on fecal flora, properties of feces, .BETA.-glucuronidase, and levels of serum lipid in healthy men.

The effects of corn fiber intake (6 and 12 g/day for 10 days) on the fecal weight, moisture, neutral detergent fiber (NDF), pH, microflora and β-glucuronidase activity, and on the serum lipids were investigated in five healthy men. Fecal weight and NDF increased depending on the fiber dose, whereas fecal moisture decreased. No remarkable change in fecal microflora was observed. Fecal β-glucuronidase activities (per gram of wet feces and daily output) were dose-dependently decreased by corn fiber intake. The levels of serum lipids did not change. These results show that corn fiber intake yielded an increase of fecal weight and a reduction of fecal β-glucuronidase activity.

Effect of Preventing Coprophagy in the Rat on Neutral Detergent Fiber Digestibility and Apparent Calcium Absorption

The effect of coprophagy on apparent neutral detergent fiber (NDF) digestibility, and calcium absorption was evaluated by housing rats in four types of cages: regular, metabolic, and two anticoprophagy cages: a short linear tube cage which allowed the rat forward and backward movement of about one-half a body length and a long tube cage assembled to form a square which allowed the rat to move in one direction through the tube but not turn around. Three-day weight gains of animals in the regular or metabolism cages were greater than those of rats housed in either anticoprophagy cage. In contrast, average food intake did not differ among the four housing conditions. Wet, but not dry, fecal weights were greater in the two groups of rats in the anticoprophagy cages. Neither fecal NDF (% dry wt) nor apparent NDF digestibility was affected by housing conditions. Apparent calcium absorption was decreased by the anticoprophagy housing. The differences in body weight and apparent calcium absorption suggest that prevention of coprophagy in the rats produces significant changes in the efficiency of food and nutrient utilization. The failure to detect differences in NDF digestibility indicates that coprophagy has little impact on the study of fiber digestibility.

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The purpose of this pilot study was to evaluate possible ways to determine compliance with a dietary fiber supplement. A wheat bran supplement (30 g daily) significantly increased mean daily wet and dry stool weights (SW) in 7 adults, when compared to SW during an ad libitum low-fiber diet (paired t-test, P less than .01). Because unpaired data would be used during a clinical trial, distribution of the 7 ad libitum low-fiber mean SW observations was used to establish a reference distribution and an upper confidence limit against which the bran supplement SW could be compared. Only one of the seven bran supplement mean SW was above the confidence limit of the low-fiber period, independent of the number of days of collection (2-10) used to calculate the individual mean daily SW. Total fecal output over varying periods of time (2-10 days) suffered the same intersubject and intrasubject variability. Most (5-6) of the bran mean daily SW were above the group mean SW of the low-fiber period. However, this dose of bran was large enough to significantly decrease calcium absorption, and differences in SW produced by lower doses of wheat bran would probably not be as great. The bulk (greater than or equal to 80%) of a single dose of a fecal marker, chromium sesquioxide, which could be incorporated into a specific day's fiber supplement, was recovered in 5 days of excretion during the control period and in 4 days during the bran period. However, the blue color of the chromium before ingestion is clearly a negative feature. Another marker, polyethylene glycol, could not be recovered in excreta when transient time was 4 days or more. In a separate study, demonstration of very little overlap in the concentration of fecal neutral detergent fiber between the control and bran periods suggests that fecal fiber may be a marker of compliance with a fiber supplement.

Effects of antimicrobial therapy on faecal bulking.

It has recently been postulated that dietary fibre acts as a substrate for colonic flora, and that the resultant microbial growth bulks the faeces. Antimicrobial therapy was used in this study to assess the effect of reduction in colonic microbial proliferation on faecal output in human subjects on a constant dietary fibre intake. Six healthy young male subjects were maintained on constant daily diets and metronidazole (1 g/day) and ampicillin (1 g/day) were administered in divided doses for one week after an initial baseline study period of two weeks. After antimicrobial therapy, mean faecal weights rose from 176.0 +/- 27.0 g to 348.1 +/- 37.7 g/day. Faecal solids increased from 32.9 +/- 4.2 g to 46.1 +/- 5.8 g/day. Faecal neutral detergent fibre increased from 1.92 +/- 0.42 g to 15.19 +/- 2.58 g/day. The mean transit times and mean daily faecal nitrogen remained the same, both before and after treatment. Substantial breakdown of dietary fibre occurs in the human colon which may decrease faecal bulk, suggesting that water holding by dietary fibre is probably of greater importance for faecal bulking.

Composition of Fecal Fiber from Human Subjects

This research addresses two problems of fecal fiber analysis: the nitrogen in fecal neutral detergent fiber (NDF); and the impact of sodium sulfite on NDF yield and composition. Fecal samples for analysis were collected from healthy adults during a study of the effect of a wheat bran supplement on bowel function. When sodium sulfite, originally a component of neutral detergent solution, was omitted, the yield of fecal NDF, the concentration of apparent lignin in the NDF and the amount of nitrogen recovered in both the NDF residue and the lignin increased. These data support a previous report by Van Soest that the sulfite attacks lignin. We present evidence that the effect of sodium sulfite also could be one of inhibiting the formation of Maillard products, which are detected as lignin, during the reflux step of the NDF method. Three different fractions of nitrogen were identified in fecal NDF: the fraction eliminated by sodium sulfite; a fraction removed by dilute acid; and the fraction that remained in Klason lignin. Apparent NDF digestibilities were calculated several ways by using correction factors to account for this nitrogen. Only the subtraction of Klason lignin from fecal NDF eliminated the one negative digestibility we observed.

Determination and Apparent Digestibility of Neutral Detergent Fiber Monosaccharides in Women

The neutral monosaccharides in neutral detergent fiber (NDF) extracted from low and high cellulose diets and from feces excreted by seven women consuming the same diet were determined. In addition, apparent digestibilities of the NDF neutral monosaccharides during consumption of both diets were compared. Diets were of constant daily composition and differed only in that the high fiber diet contained 16 g/day of Solka Floc. NDF residues from food and feces were hydrolyzed by the Saeman procedure and the neutral saccharides measured by high performance liquid chromatography. More than 75% of the food NDF from both diets was glucose. Mean fecal NDF was 77% glucose during feeding of the low fiber diet, 89% glucose during the high fiber diet. Xylose was the next most common monosaccharide, accounting for 6–16% of the monosaccharides detected in food and fecal NDF. Concentrations of the other sugars, arabinose, cellobiose, mannose, galactose and rhamnose, ranged from 1 to 6%. Apparent digestibility of the sugars decreased significantly when Solka Floc was consumed: glucose from 85 to 48%; xylose from 76 to 57%; arabinose 89 to 73%; and mannose 86 to 43%. These data indicate that the monosaccharides in NDF from a representative low fiber diet are degraded extensively in the gut, and that adding Solka Floc to the diet decreases the digestibility of all fiber-derived monosaccharides.

Apparent digestibility of neutral detergent fiber in elderly and young adults

These experiments assessed the ability of the neutral detergent fiber (NDF) method to remove starch and nitrogen from food NDF residues, and nitrogen and endogenous secretions from fecal NDF residues; and compared indices of bowel function, including apparent NDF digestibility, of nine elderly subjects to those of six young women. Subjects consumed similar, controlled "low fiber" diets containing foods typically eaten in the United States. Nitrogen and starch contents of food composite NDF were determined in NDF obtained by the hog alpha amylase modification of the Van Soest procedure, whereas the nitrogen content of fecal NDF was determined using NDF obtained by the unmodified procedure. The modified Van Soest method adequately removed nitrogen and starch from food NDF, but fecal NDF contained nitrogen. Both groups digested the majority of the NDF, 63 and 70% for the elderly and young subjects, respectively. Apparent fiber digestibility, which was measured several times in each subject, increased to 69 and 75% for the two groups, respectively, when a correction was made for the nitrogen in the fecal NDF. Mean gastrointestinal transit time and frequency of defecation of the two age groups were comparable, whereas mean daily wet and dry stool weights of the elderly were larger than those of the young women. These results suggest that the bowel of the elderly may function as well as that of the young adult.