The influence of dietary fibre sources on growth,feed efficiency and digestibilities of dry matter and protein in rats

Hulls from Tower canola (TCH), Regent canola (RCH) and soya beans (SBH) were included at 10 or 20% in soya bean meal based diets for rats, to compare the effects of these fibre sources on growth, feed consumption, feed efficiency and dry matter and protein digestibilities. A soya bean meal based control diet and another diet containing a purified fibre source (Alphafloc) at a 10% level, were included for a further comparison. Each of the diets was fed to six rats in a 4-week feeding trial. The diets gave similar weight gain, feed consumption and feed efficiency values. The control diet had the highest mean coefficient of dry matter digestibility (80.8%) and the 20% SBH and Alphafloc diets had the lowest (72.4 and 72.2%). The canola hull and 10% SBH and Alphafloc diets had intermediate values (73.2–75.0%). There was a highly significant negative correlation between the dietary fibre content and the dry matter digestibility of the diets. The control and Alphafloc diets showed the highest and similar apparent (81.4 and 79.9%) and true (86.8 and 85.3%) digestibility values for dietary protein. The 20% canola and soya bean hull diets showed the lowest apparent (71.4–73.7%) and true (76.9–79.4%) digestibility coefficients. The 10% canola and soya bean hull diets had intermediate apparent and true protein digestibility values (73.2-75.3 and 78.4–80.6%, respectively). The chemical analysis of the fibre sources showed that Alphafloc had the highest cellulose content (88%) and the lowest lignin content (0.6%), while canola hulls had the lowest cellulose content (25.4–28.4%) and the highest lignin content (26.6–28.9%). Soya bean hulls had intermediate cellulose (50%) and low lignin (1.3%) contents. The results suggest that cellulose did not have a detrimental effect on the dietary protein digestibility but lignin and/or some other undetermined factors in the hulls had an adverse effect on protein digestibility.     

Physiological Responses of Rats to High Fiber Bread Diets Containing Several Sources of Hulls or Bran

Fiber-supplemented breads, prepared by replacing 7.5% of the hard wheat flour with field pea, flax or sunflower hulls, wheat bran or microcrystalline cellulose, were evaluated for breadmaking characteristics and physiological effects on rats. Cellulose-supplemented dough and bread resembled the straight-grade wheat bread while pea hull and wheat bran breads were similar to whole wheat bread. Flax and sunflower hulls had adverse effects on dough mixograph properties, loaf volume and crumb characteristics while sunflower hulls also contributed grittiness and aftertaste in taste panel evaluations. The fiber-supplemented breads, when fed to weanling rats, gave similar feed consumptions, weight gains and serum cholesterol levels as rats fed the whole wheat bread. Pea hulls increased daily fecal weight and, with coarse sunflower hulls, decreased dry matter digestibility. Fine wheat bran and fine sunflower hulls in the bread diets were associated with low fecal weight, low fecal volume, high fecal density and high digestibility of dry matter.     

Short‐term feeding of fermentable dietary fibres influences the gut microbiota composition and metabolic activity in rats

This study investigated the effects of dietary fibres on gut bacterial abundance and metabolic activity in rats fed short‐term. Faecal samples from rats fed for 7 days showed differences in the effects of dietary fibres on gut bacterial populations. Broccoli fibre, inulin, potato fibre and potato resistant starch significantly increased the faecal Bacteroides‐Prevotella‐Porphyromonas group compared with cellulose. Growth of pathogenic bacteria such as Clostridium perfringens, Escherichia coli and Enterococcus spp. was decreased significantly in rats fed barley β‐glucan, citrus pectin, inulin and broccoli fibre diets. An increase in Bifidobacterium spp. and butyric acid levels, the so‐called bifidogenic and butyrogenic effects, was observed in rats fed inulin and potato fibre diets. Organic acid concentrations and polysaccharide contents in the rat faeces confirm the fermentability of dietary fibres in the gut. This study demonstrates the positive effects of plant‐sourced dietary fibres on gut microbiota composition and metabolic activity.     

High apparent ileal digestibility of amino acids in raw and germinated faba bean (Vicia faba)‐ and chickpea (Cicer arietinum)‐based diets for rats

The effects of germinated faba bean (Vicia faba minor var Alameda)‐ and chickpea (Cicer arietinum kabuli var Athenas)‐based diets on performance, N utilisation, amino acid ileal digestibility and plasma concentrations were studied in growing male Wistar rats. Raw and germinated faba bean and chickpea seed meals were incorporated in essential amino acid‐supplemented and energy‐equalised diets as the only sources of protein. A lactalbumin‐based diet equalised in protein (100 g kg^?1) and digestible energy (15.5 kJ g^?1) with the test diets was used as control. Weight gains, gain/feed ratios, N retention and NPU values of animals fed raw or germinated legumes were lower than those of rats given the control (lactalbumin) diet, while faecal dry weights were higher. However, N retention and NPU values of rats fed germinated faba bean diets were higher and faecal dry weights lower than those of animals fed non‐germinated faba bean diets. Liver and thymus fresh and dry relative weights were lower than controls for all legume diets, whilst small intestine, caecum and colon relative weights were higher than controls for non‐germinated faba beans and chickpeas either germinated or not. Caecum and colon fresh and dry relative weights of rats fed germinated faba bean seeds were lower than those of rats fed non‐germinated faba beans and not different from controls. Except for aspartic acid and proline in rats fed raw faba bean diets, apparent ileal digestibilities of amino acids were not different or higher in rats fed legume diets as compared with controls. Except for arginine, apparent ileal amino acid digestibility was higher for germinated than for non‐germinated faba bean seeds. The amounts of glycine, arginine and ornithine in plasma significantly increased whilst those of threonine, alanine, leucine and lysine decreased with respect to controls in faba bean‐ or chickpea‐fed rats, either germinated or not. We conclude that (a) germination of faba bean seeds gave rise to a significant (P < 0.01) but limited improvement in performance, N retention and apparent ileal digestibilities of some amino acids in growing rats compared with non‐germinated seeds, while there was no detectable effect in the case of germinated chickpea seeds, and (b) the apparent ileal amino acid digestibility of essential amino acid‐supplemented diets based on faba bean or chickpea meals, either germinated or not, is similar or even higher than controls. © 2002 Society of Chemical Industry     

Evaluation of gastrointestinal transit in rats fed dietary fibres differing in their susceptibility to large intestine fermentation

The rate and extent of in situ digesta transit after ingestion of diets containing dietary fibres differing in their susceptibility to large intestine fermentation were investigated. One hundred and twenty rats were fed diets containing 7.5% cellulose, inulin, potato fibre or maize starch for 3 days, then the same diets with titanium dioxide (TiO₂) for 3 days, followed by diets without TiO₂ for 2 days. In all diets, TiO₂ ratios rapidly increased within 24 h and reached a maximum level in duodenum, caecum and colon within 2–3 days. Inulin, potato fibre and maize starch-fed rats showed higher levels of caecal short-chain fatty acids, lower faecal polysaccharide concentrations, and reduced faecal output than the rats fed cellulose. Inulin was highly susceptible to caecal microbial fermentation compared to the other dietary fibres. Transit of these dietary fibres through the GI tract was rapid, and the rate of digesta transit was not affected by dietary fibre fermentability in the large intestine.     

The effect of wheat bran on the excretion of cadmium in rats

The influence of wheat bran as a source of dietary fibre on the excretion of ingested cadmium from diet was studied. The cadmium contents in the diets, faeces, urine, liver, kidney and spleen were determined, as well as the weight gains, the relative weights of the cited organs, and the levels of alkaline phosphatase in serum. No evidence is provided that an increasing portion of wheat bran in the diets induced an increase in cadmium excretion. Changes in the studied toxicity parameters were not found.     

Effect of Hard Red Spring Wheat Bran on the Bioavailability of Lipid-Soluble Vitamins and Growth of Rats Fed for 56 Days

Semipurified diets containing either 0, 5 or 20% wheat bran were fed ad libitum to male Sprague-Dawley rats. Significant increases in weights (P < 0.05) were found for the stomach, 32.6 ± 8.7%, and for the large intestine, 14.5 ± 4.8%, in rats fed 20% wheat bran compared to the control rats fed 0% wheat bran. Wheat bran consumption had no effect on plasma vitamin E or plasma vitamin A levels after 56 days of feeding; however, plasma vitamin A and vitamin E levels were shown to decline after 6 weeks and 5 weeks respectively, on the wheat bran diets. These studies suggest that some metabolic modifications induced by dietary wheat bran undergo reversible adaptations that are time dependent.     

Effects of two contrasting dietary fibres on starch digestion,short‐chain fatty acid production and transit time in rats

Dietary fibres may cause dietary starch to escape digestion in the small intestine and enter the large intestine. If this results from the dietary fibres reducing the gastrointestinal transit time, those dietary fibres that reduce this the most would be expected to cause the most starch to escape digestion. We tested in rats the relative abilities of two contrasting dietary fibres, apple pectin (a soluble dietary fibre) and wheat straw (an insoluble, lignified dietary fibre), to reduce the whole gut transit time and to cause dietary starch to escape digestion. We provided male Wistar rats with a control, modified AIN‐76™ diet containing 20% fat but no dietary fibre, and with this diet containing 10% dietary fibre; the dietary fibre replaced the equivalent weight of starch in the control diet. Both dietary fibres, but particularly wheat straw, reduced the transit time compared with the fibre‐free control diet. Pectin, but not wheat straw, resulted in substantial amounts of starch in the caecal contents. This effect may result from the pectin increasing the viscosity of the digesta or causing it to gel. Large amounts of short‐chain fatty acids were found only in the caeca of rats provided with pectin. © 2000 Society of Chemical Industry     

Influence of fibre from different cereals on the rheological characteristics of wheat flour dough and on biscuit quality

Demand for health oriented products such as sugar-free, low calorie and high fibre products is increasing. One such recent trend is to increase the fibre content in food products to overcome health problems such as hypertension, diabetes, and colon cancer, among others. Consumption of high fibre products consisting of indigestible cellulose, hemicellulose, lignin and gums have several health benefits. Apart from these benefits, β-glucan-rich fibres have the benefit of reducing the absorption of glucose. Fibre sources from wheat, rice, oat and barley were used to study their influence on rheological characteristics of wheat flour dough and biscuit making quality. Ash, total protein and dietary fibre content of bran samples ranged between 4% and 10%, 12% and 14% and 20.4% and 49.5%, respectively. Farinograph characteristics of the wheat flour-bran blends showed increase in water absorption from 60.3% to 76.3% with increase in the level of bran from 0% to 40%. The resistance to extension values as well as extensibility of the dough decreased with increase in the bran level. The spread ratio of the biscuits prepared from wheat, rice and oat bran blends decreased from 8.38 to 7.52, whereas the same increased to 9.3 for biscuits prepared from barley bran blends. The breaking strength values of biscuits ranged between 1.34 and 3.83 kg. Highly acceptable biscuits could be obtained by incorporating 30% of oat bran or 20% of barley bran in the formulation.     

Does a mix of plant-based dietary fibre affect milk protein true digestibility? An in-vivo study

Milk protein is easily digestible. However, some plant-based dietary fibres (DF) could impact protein bioavailability. The effect of DF fortification on the true protein digestibility (TPD) of milk was evaluated following the rat balance method. Four groups of rats were fed four different diets. Three diets comprised milk protein as a source of protein along with either DF Blend I (a mix of psyllium husk, oat fibre, microcrystalline cellulose and inulin) or Blend II (psyllium husk, oat bran, wheat fibre and inulin) or cellulose (as control). The fourth group was nitrogen-free with cellulose (5%). The TPD of milk remained statistically unaffected (ANOVA, P > 0.05), indicating that DF blends are suitable for milk fortification.     

Composition and Physiological Properties of Several Sources of Dietary Fiber

Dietary fiber sources containing 31 – 99% of neutral detergent fiber were evaluated for functional properties and physiological effects on rats. The high water hydration capacity of mucilage-containing psyllium seeds and flax hulls were associated with low digestibility, high volume and weight of feces, and low serum triglycerides. Mustard hulls and sunflower heads, which contained less mucilage or pectin, were intermediate in water hydration capacity and as bulking agents in the gastrointestinal tract. Fiber sources rich in hemicellulose and lignin (wheat bran, sunflower hulls) had high fat absorption properties, digestibility and serum triglycerides. Pea hulls and cellulose showed less strong functional properties as sources of dietary fiber.     

Loss of selected water-insoluble polysaccharides and component neutral sugars from swede (Brassica napus (cv. danestone)) and cereal bran measured during digestion in the pig caecum

Sources of dietary fibre with a high pentose sugar content have been shown to have the greatest effect in promoting faecal bulking, though no underlying reason for this has been found. Pentose-containing polysaccharides in dietary fibre are, in isolation, as degradable as other polysaccharides, though their known association with lignin could be important in helping to maintain the structural integrity and hence the bulking ability of a fibre source. Using a modified nylon bag technique, the potential digestibility of fibre prepared from a source rich in pentose sugars (cereal bran) and a source poor in pentose sugars (Swede; Brassica napus, cv. Danestone) was estimated in the pig caecum. Swede fibre was effectively completely degraded (within 18 h) but in bran 100% digestion was not achieved even with extended incubation. Rates of fibre component loss, estimated from material recovered from the nylon bags, showed that different fibre components were degraded at different rates and that the rate of degradation was not always linear. In swede xylose was less readily lost than other fibre components and the rate was non-linear whilst in bran xylose was preferentially lost and at a linear rate. In bran arabinose was less readily lost. The results showed that the bulking effects of fibre sources with a high pentose sugar content were unlikely to be due solely to pentose content. Differences in rates of digestion suggested that different linkage groups contained within a component may be able to modify the degree of fibre digestion, most probably by the linkage of specific pentosans to lignin.     

Revised method for quantitating dietary fibre components

A modification to existing methods of fibre separation and quantification has been proposed. The scheme involves lipid removal with diethyl ether; removal of water-soluble components and quantification of water-soluble fibre components; removal of water-insoluble starch; protein removal; pectin analyses; water-insoluble hemicellulose quantification; cellulose quantification; and lignin quantification. Simultaneous equations were used to compensate for hexose absorption at the same wavelength as pentoses. Recovery values for individual steps ranged from 90% using a low methoxy pectin to 98% using cornstarch, cellulose, agar or carrageenan. The scheme was used to analyse fibre components in seven wheat brans, maize bran, oat bran, soya bean hulls, potato and apple. Recoveries of fibre and other proximate analyses ranged from 95.9 to 104.7%. Remaining methodological problems are also discussed.     

Water Holding Capacity of Hemicelluloses from Fruits, Vegetables and Wheat Bran

The water-holding capacities of freeze-dried bean, cabbage, lettuce, onion, peach, pear, pumpkin, tomato, wheat bran and their hemicelluloses were determined by the centrifugation method. Cabbage had the greatest water-holding capacity at 35.8g of water per gram of dry food; bran the lowest at 5.2g water per gram. The waterholding capacity (WHC) of the hemicelluloses from fruits and vegetables varied considerably from 3.3 g/g in beans to 12.0 g/g from cabbage. Hemicelluloses extracted from wheat bran showed a marked increase in WHC from 5.2 g/g of water per gram of‘whole’bran to 22.8 g/g for hemicellulose. This decreased to 15.3g of water bound by hemicellulose that had been extracted after chlorite delignification. WHC of hemicelluloses from wheat bran and cabbage may account for their ability to increase stool weight.     

Effect of high-fat diets supplemented with okara soybean by-product on lipid profiles of plasma,liver and faeces in Syrian hamsters

The main components of okara, a by-product from soybean, are dietary fibre and protein. In this study we fed okara based diets with different amounts of fibre, protein and isoflavones to determine their effect on the lipid profile in the plasma, liver and faeces of an animal model. Male golden Syrian hamsters were fed high-fat diets supplemented with okara for 3 weeks. The supplemented diets contained 13% or 20% of okara fibre (OK-13 and OK-20), low-protein okara with 13% of fibre (OK1-13), and isoflavone-free okara with 13% of fibre (OK2-13). Okara supplemented diets did not produce significant differences in the feed intake or body weight gain (p > 0.05). The plasma levels of triglycerides, VLDL- plus LDL cholesterol and total cholesterol in hamsters fed OK-20 decreased significantly (p < 0.05) with respect to the 20% control group (C-20). However, no significant differences (p > 0.05) were found in LDL- and HDL-cholesterol plasma levels in all experiments. Total lipids, triglycerides, total and esterified cholesterol concentrations in liver were reduced by OK-20 diet. Regarding the hamsters fed OK-13 diets, the mean values of the total lipid, triglyceride and cholesterol in the plasma and liver decreased as compared to the control (C-13), but the differences were not statistically significant. All of the okara diets assayed increased the faecal excretion of total lipids, triglycerides, free cholesterol and total nitrogen (p < 0.05) compared to their respective controls. Our results suggest that the main components of okara, dietary fibre and protein, could be related with the total lipids and cholesterol decrease in the plasma and liver, as well as with the faecal output increase in high-fat fed hamsters. Okara might play an interesting role in the prevention of hyperlipidemia and could be used as a natural ingredient or supplement for functional food preparation.     

Lipid-Soluble Vitamins in Blood and Liver of Rats Fed a Diet Containing Hard Red Spring Wheat Bran

Semipurified diets containing either 0 or 20% wheat bran were fed ad libitum to male Sprague-Dawley rats for 9 wk. Wheat bran consumption had no effect on vitamin A or E levels in plasma, leukocytes, or liver, nor on vitamin E levels in erythrocytes of these rats after 9 wk of feeding. However, during the study period, values showed transient declines. Both vitamins showed similar declines in leukocytes and livers of the bran-fed rats. Erythrocyte vitamin E levels also were influenced by the wheat bran diet but no erythrocyte vitamin A could be detected. Thus, rats adapt to diets containing high levels of wheat brans, perhaps by metabolic or gastrointestinal modifications.     

Physicochemical characterisation of dietary fibre components and their ability to bind some process-induced mutagenic heterocyclic amines,Trp-P-1, Trp-P-2, AαC and MeAαC

The physicochemical properties of potato fibre, wheat bran and oat samples were investigated, along with their binding capability to heterocyclic amines (HCAs). Potato fibre displayed highest total dietary fibre content (71.8/100 g dry weight basis, dwb), followed by wheat bran (57.2/100 g dwb) and oat sample 2 (53.0/100 g dwb). Oat samples 1, 3 and 4 displayed considerably lower dietary fibre content (20.5–28.8/100 g, dwb). Oat samples 3 and 4 displayed highest soluble fibre content (70–83%), and oat sample 3 also displayed highest swelling and water retention capacity (WRC). Dietary fibre samples, except samples 3 and 4, displayed improved binding to HCAs as sample weight increased. The behaviour of wheat bran and potato fibre was similar to oat samples 1 and 2. Binding of MeAαC was comparatively greater than that of other HCAs. Dietary fibre fractions with high insoluble fibre and functional groups of HCAs may significantly contribute to the binding capacity.     

In vitro digestibility and colonic fermentability of aleurone isolated from wheat bran

Two aleurone preparations, isolated from wheat bran, with different levels of tissue purity, were compared to the wheat bran starting material. Chemical composition, in vitro digestibility and in vitro fermentability were investigated and microscopy was used to visualize morphological changes. Arabinoxylans constituted the main part of the dietary fibre fraction. However, the degree of branching was found to be lower in arabinoxylans from aleurone than in that from original bran. Due to the high fibre content, in vitro digestibility was rather low but digestible compounds were largely eliminated. In vitro fermentability using fresh human faecal material turned out to be higher in aleurone than in wheat bran. Moreover, the degree of purity of the aleurone preparations influenced the amount of fermentation products. Proportions of the main short chain fatty acids were very similar in all samples, with ratios of propionate and butyrate slightly above average compared to other dietary fibre sources. Arabinoxylans from aleurone were virtually completely degraded within 8 h, whereas with wheat bran, substantial amounts were still present after 24 h. Moreover, increasing arabinose:xylose ratios during fermentation suggested a better fermentability of arabinoxylans with a lower branching degree. Microscopic investigations confirmed the better fermentability of aleurone compared to wheat bran. In addition, a specific breakdown pattern of aleurone cell walls could be observed.     

Effects of Particle Size and Breadmaking on Physiological Responses of Meal-Fed Rats to AACC Wheat Bran

Adult rats were meal-fed diets containing 20% AACC certified hard red spring wheat bran (as received, ground, incorporated into bread) for 12 days to determine the short-term processing-induced effects on gastrointestinal function and serum lipids. Fecal nitrogen, fecal fat, transit time and serum triglyceride levels were influenced by the consumption of wheat bran, but not by the grinding or breadmaking procedures. Reduction of bran particle size decreased dietary hemicellulose and reduced fecal bulk as well as defecation frequency. Incorporating bran into bread reduced dietary neutral detergent fiber (NDF), reduced intestinal passage rate of the ground wheat bran and decreased degradation of dietary fiber components in the unground wheat bran.     

Organs relative weight and plasma amino acid concentrations in rats fed diets based on whole legume (faba bean,lupin, chickpea,defatted soybean) seed meals or their fractions

The effects on organ relative weights (g per 100 g bw) and plasma amino acid concentrations of diets based in legume (faba bean (Vicia faba), lupin (Lupinus angustifolius), chickpea (Cicer arietinum) and soybean (Glycine max)) seed meals as the only source of protein were studied with growing rats using lactalbumin or casein as controls. Also, legume seed meal extracted globulins were included in control diets replacing lactalbumin to produce legume globulin‐based diets, and legume residue fractions, containing most of the starch and/or insoluble fibre (NSP+lignin) from the seed meals, were included in control diets to reach the same amounts present in whole legume seed meal diets. All experimental diets were formulated to contain the same amounts of protein (100 g kg⁻¹) and energy (15.5 kJ g⁻¹), and were supplemented with essential amino acids. Compared with lactalbumin, higher relative weights of gastrointestinal sections were determined in rats fed legume seed meals or their corresponding residue fractions. On the contrary, spleen relative weight was lower in rats fed diets containing lupin, chickpea or soybean meals or extracted globulins, while residue fractions had no effect on it. Thymus relative weight was also lower in rats fed whole chickpea seed meal or any of the extracted legume globulins. Except for chickpea meal, animals fed legume‐ or legume protein‐based diets had lower liver relative weights than controls. Lower proportions (mg g⁻¹ tissue) of glycogen, and lower total protein and RNA, were also determined in the livers of rats fed lupin seed meal. Free plasma concentrations (mM litre ⁻¹) of glycine, histidine and arginine were higher, and threonine, leucine and lysine were lower, in rats fed diets based in all legume seed meals of their respective globulin proteins. The possible reasons and implications of these results are discussed. © 1999 Society of Chemical Industry