Evaluation of large-intestinal parameters associated with dietary treatments designed to reduce the occurrence of swine dysentery

Diets containing soluble NSP (sNSP) and resistant starch (RS) increase hindgut fermentation in pigs, which in turn increases the incidence of swine dysentery (SD) after infection with the intestinal spirochaete Brachyspira hyodysenteriae. In the present study pigs were fed diets based on either wheat or sorghum, fed either raw or treated by extrusion, and/or with the addition of dietary enzymes to reduce RS and/or sNSP content. The aim was to determine the effects of these treatments on pig performance, large intestinal fermentation and expression of SD. Weaned pigs (n 132) were fed experimental diets for 4 weeks, when half the pigs in each treatment group were euthanased and samples collected to assess the influence of the diet on hindgut fermentation. The remaining pigs then were infected with B. hyodysenteriae, and monitored for development of SD. In general, compared with pigs fed raw wheat, fermentation in all parts of the large intestine was reduced either by feeding raw sorghum-based diets, or by feeding diets that were extruded. The addition of enzymes that degrade RS or sNSP reduced fermentation only in the distal parts of the large intestine. The incidence of SD was lower in pigs fed sorghum-based diets, and some of the extruded diets, but none of the dietary treatments offered full protection against SD. Multiple regression analysis of the results from all three experiments showed that colonisation by spirochaetes was highly related to dietary sNSP concentrations, whilst development of SD was similarly influenced by RS content of the diet.     

Rye bread in the diet of pigs enhances the formation of enterolactone and increases its levels in plasma,urine and feces

To obtain new insight into the quantitative and qualitative metabolism of rye and wheat lignans, we performed three series of experiments with catheterized pigs. Two diets with similar levels of dietary fiber and macronutrients but with contrasting levels of plant lignans (isolariciresinol, lariciresinol, matairesinol, pinoresinol, secoisolariciresinol and syringaresinol) were prepared from rye (high in lignans) and wheat (low in lignans) soft and crisp breads. In two series of experiments we quantified the uptake from the gut of enterolactone in four pigs fitted with catheters in the portal vein and mesenteric artery and with an ultrasonic flow probe attached to the portal vein to monitor the blood flow. In a third study with six pigs, we quantified the bioavailability of the plant lignans that can be converted to enterolactone (lariciresinol, matairesinol, pinoresinol, secoisolariciresinol and syringaresinol) and the concentration in the peripheral blood. Plant and mammalian lignans in diets and stool were analyzed by isotope dilution gas chromatography-mass spectrometry and enterolactone in plasma and urine determined by time-resolved fluoroimmunoassay. There was a significantly higher formation of enterolactone in pigs fed the rye diet, and higher fecal and urinary excretion and circulating levels of mammalian lignans than in pigs fed the wheat diet. The conversion of mammalian lignan precursors to enterolactone was 48% with the wheat diet and 60% with the rye diet. Mammalian lignans are absorbed by passive diffusion from the large intestine and a substantial fraction of the absorbed mammalian lignans undergoes enterohepatic circulation, resulting in low diurnal variation in plasma levels of enterolactone.     

Rye bread enhances the production and plasma concentration of butyrate but not the plasma concentrations of glucose and insulin in pigs

The present investigation was undertaken to study the gastrointestinal and physiologic properties of diets based on soft and crisp wheat and rye breads similar in dietary fiber (DF; 230-235 g/kg dry matter) but with different proportions of the main DF polymers: in wheat, cellulose, and in rye, arabinoxylans (AX). The 2 diets provided all macronutrients; consequently, they had lower fat and sugar contents and a higher DF content than human mixed diets. The nutritional properties were studied in experiments in which pigs with cannulated ilea and catheterized portal veins and mesenteric arteries served as models for humans. The characteristics studied were degradation of nutrients, flow at the ileum, fecal output, absorption of nutrients deriving from the assimilation of cereal carbohydrates, and the insulin response. Apparent viscosity at the terminal small intestine, the ileal flow of water, flow and digestibility of noncarbohydrate constituents, but not of carbohydrates at the terminal ileum or the plasma concentrations of glucose and insulin, were higher when pigs consumed the rye compared with the wheat diet. The 2 diets provided approximately equal amounts of carbohydrates available for fermentation in the large intestine but because AX from the rye diet was more degradable than cellulose from the wheat diet, the quantitative degradation in the large intestine was more than twice as high when pigs consumed the former compared with the latter diet. The consequences included moister feces and significantly enhanced gut production and plasma concentrations of butyrate when pigs consumed the rye diet compared with the wheat diet.     

Consumption of wholemeal rye bread increases serum concentrations and urinary excretion of enterolactone compared with consumption of white wheat bread in healthy Finnish men and women

Rye is an important source of plant lignans in Finland. In the present crossover trial we wanted to study the effect of rye bread as part of the usual diet on serum and urine enterolactone (ENL) concentrations in healthy volunteers. Eighteen men aged 43 (sem 2.0) years and twenty-one women aged 43 (sem 1.6) years consumed wholemeal rye bread and white wheat bread in random order for 4 weeks. The bread periods were separated by a 4 week wash-out period. The breads provided at least 20% of the daily energy intake. The mean intakes of rye bread were 219 (sem 14.6) and 162 (sem 5.3) g/d and those of wheat bread were 200 (sem 9.6) and 153 (sem 5.8) g/d for men and women respectively. Blood samples were collected from all subjects and three 24 h urine samples were collected from ten men and twelve women at the end of both bread periods for the determination of serum concentration and urinary excretion of ENL. The mean serum ENL concentrations in both men and women at the beginning of baseline period and at the end of the rye-bread period remained constant and were significantly higher than those at the end of the wheat-bread period. Correspondingly, daily urinary ENL excretion increased significantly during the rye-bread period compared with the wheat-bread period and was 5- and 10-fold higher in men and women respectively in comparison with the amount of plant lignan precursors measured in the rye bread. These data indicate the presence of other precursors for ENL in rye which are not detected by the current method of measuring plant lignans in food. The possible role of fibre in enhancement of the formation of mammalian lignans from their plant precursors in the gut also remains to be determined.     

A viscous fibre (methylcellulose) lowers blood glucose and plasma triacylglycerols and increases liver glycogen independently of volatile fatty acid production in the rat

1. Adult male rats were maintained on diets containing 80 g methylcellulose/kg of low (25 cP), medium (400 cP) and high (1500 cP) viscosity. 2. After 10 d, the viscosity of stomach and caecal contents was found to have increased in proportion to that of the dietary fibre. Concentrations of volatile fatty acids in caecal digesta were lowest with the high-viscosity fibre but acetate was the major acid present with all three diets. Acetate was the only acid found in significant quantities in hepatic portal venous plasma and concentrations of this acid were unaffected by diet. 3. Concentrations of glucose in arterial blood were low with the medium- and high-viscosity diets while the content of liver glycogen was high. These effects of fibre were not directly on glucose absorption as the intestines were net removers of the hexose at the time of sampling. 4. Hepatic lipogenesis and plasma triacylglycerol concentrations were both higher in rats fed on the low-viscosity fibre. Plasma cholesterol concentrations, hepatic cholesterol synthesis and faecal bile acid excretion were not altered by dietary fibre viscosity. 5. We conclude that the effects of dietary fibre on carbohydrate absorption and storage and fatty acid synthesis are a function of the viscosity of the fibre in solution, high viscosity slowing the digestion and absorption of nutrients in the small intestine. Large-bowel microbial fermentation is not of direct significance to these events. In contrast, effects of fibre polysaccharides on sterol metabolism seem not to be related to their rheological properties.     

Fiber-degrading enzyme increases body weight and total serum cholesterol in broiler chickens fed a rye-based diet

Broiler chickens were fed diets based on either outer or inner endosperm from rye. These diets were fed with or without a fiber degrading enzyme to study the effects of the dietary fiber fraction on production results, body composition, serum lipid concentrations and apparent ileal digestibility of nutrients. Elimination of the dietary fiber effect by the enzyme generally improved the production results and caused an increase in total serum cholesterol concentrations. On average, at d 21 of the experiment chickens fed the enzyme supplemented outer endosperm diet had body weights and serum total cholesterol concentrations -23% and 37% higher, respectively, than those of birds fed the corresponding unsupplemented diet. The body fat content tended to be higher and the protein content was generally lower in chickens fed enzyme-supplemented diets. Chickens fed the unsupplemented outer endosperm diet had a low apparent ileal crude fat digestibility of only 23%, and birds fed the enzyme-supplemented diet had crude fat digestibility that was 113% higher but still lower than that of birds fed the inner endosperm diet. Birds fed enzyme-supplemented diets generally had higher apparent ileal digestibilities of organic matter, crude protein, starch, crude fat and dietary fiber components.     

Rye,lignans and human health

Rye bran contains a high content not only of dietary fibre, but also of plant lignans and other bioactive compounds in the so-called dietary fibre complex. Blood concentrations of lignans such as enterolactone have been used as biomarkers of intake of lignan-rich plant food. At present,evidence from studies in human subjects does not warrant the conclusion that rye, whole grains orphyto-oestrogens protect against cancer. Some studies, however, have pointed in that direction,especially in relation to cancers of the upper digestive tract. A number of prospective epidemiological studies have clearly shown a protective effect of wholegrain cereals against myocardial infarctions. A corresponding protective effect against diabetes and ischaemic stroke(brain infarct) has also been demonstrated. It seems reasonable to assume that these protective effects are associated with one or more factors in the dietary fibre complex.     

Digesta transit in different segments of the gastrointestinal tract of pigs as affected by insoluble fibre supplied by wheat bran

Digestibility is the result of two competing processes: digestion and digesta transit. To develop or parameterise mechanistic models of digestion, both processes have to be quantified. The aim of this study was to determine the effect of insoluble dietary fibre on the transit in the gastrointestinal tract of pigs. Six barrows (33 kg initial body weight and fitted with two simple T-cannulas at the proximal duodenum and distal ileum) were used in a double 3 x 3 Latin square design. Pigs were offered diets differing in total dietary fibre content (170, 220 and 270 g/kg DM) at 4 h intervals. A single meal marked with YbO2 and Cr-EDTA was used to determine the kinetics of markers concentrations of the solid and liquid phases, respectively. The mean retention time (MRT), calculated by the method of the moments, averaged 1, 4 and 38 h in the stomach, small intestine and large intestine, respectively. Increasing the insoluble fibre content in the diet had no effect on MRT in the stomach and decreased the MRT of both phases in the small intestine (P < 0.05). In the large intestine, increasing the insoluble fibre content decreased the MRT of the liquid phase (P = 0.02) and tended to decrease the MRT of the solid phase (P = 0.06). Transit of the solid phase in the large intestine was 4-8 h slower than transit of the liquid phase. Analysis of marker excretion curves indicated that the small and large intestine should be represented mathematically to have both a tubular (propulsion) and compartmental (mixing) structure.     

Effects of dietary oat bran and diabetes on plasma and caecal volatile fatty acids in the rat

Diets high in plant fibre, particularly viscous gums, are of potential benefit in the control of diabetes in man. This study compares the effects of oat bran, one such fibre preparation, with purified cellulose on volatile fatty acid metabolism in rats fed a high carbohydrate diet. Concentrations of total volatile fatty acids were significantly higher both in hepatic portal venous plasma and caecal contents of rats fed oat bran. Major differences were also found in the relative contributions of individual acids with proportionately less acetate and more propionate and butyrate in these animals compared with rats fed cellulose. In rats fed a standard laboratory diet, diabetes induced by streptozotocin produced a sustained increase in caecal and hepatic portal venous concentrations of acetate, propionate and butyrate. Because of the high simple carbohydrate content of the experimental diet, the tolerance of diabetic rats for the bran and cellulose diets was poor and no differences in VFA metabolism were observed after 24 hr of diabetes. It is concluded that volatile fatty acid concentrations were in proportion to the probable digestibility of the source of dietary fibre and are significant metabolic fuels liable to altered metabolism by insulin insufficiency.     

The influence of dietary fiber on proliferation of intestinal mucosal cells in miniature swine may not be mediated primarily by fermentation.

Cannulated miniature pigs were used as a model for evaluating the effects of fiber-containing diets on proliferation of colonic epithelial cells. Biopsy specimens taken from the mucosa of the cecum and distal colon were incubated in [3H]thymidine and processed using autoradiography. Digesta from the cecum was analyzed for concentrations of short-chain fatty acids (SCFA), pH and volume. Cellular proliferation at both intestinal sites was influenced by the source or quantity of dietary fiber. These dietary variables also influenced SCFA concentrations and pH of cecal digesta and the volume of contents in the fermentation chamber. Cellular proliferation was not significantly correlated, however, with the quantity of water-soluble dietary fiber consumed, with SCFA concentrations or pH of the cecal digesta, or with the volume of the fermentation chamber. We suggest that the influence of dietary fiber on intestinal cell proliferation cannot be predicted from markers of the fermentation capacity of specific diets, because fiber likely influences intestinal proliferation through several interactive mechanisms, some of which include luminal factors.     

Effects of baking hulless barley on the digestibility of dietary components as measured at the ileum and in the feces in pigs

The effects of different baking conditions on the apparent digestibility of dietary components were examined in pigs with an ileal cannula. The pigs were fed a hulless barley-based diet that was 1) uncooked, 2) baked for 4 h using high moisture, low temperature (37% dry matter, 121 degrees C) conditions (HMLT), or 3) baked for 1 h using lower moisture, high temperature (48% dry matter, 204 degrees C) conditions (LMHT). Ileal digesta and fecal dry matter were not different between the three diets. Pigs fed the HMLT and LMHT diets had 4% and 2% higher starch digestibility at the ileum, respectively, than did pigs fed the uncooked diet (P less than 0.05). Total Klason lignin recovered at the terminal ileum was similar for all diets even though initial Klason lignin values for the LMHT diet were twice that of the uncooked or HMLT diet. Digestibility of non-starch polysaccharides (NSP) as measured at the ileum and in the feces of pigs fed the baked diets was about 10% higher than in pigs fed the uncooked diet (P less than 0.1). The ratio of NSP ileal digestion:NSP digestion as measured in the feces was over 0.75 for all diets. Baking increased digestibility in the barley-based diet by increasing the digestibility of starch and dietary fiber. Increasing the severity of baking (LMHT) tended to decrease digestibility compared to the mild baking (HMLT), but not significantly.     

Neonatal genetically lean and obese pigs respond differently to dietary cholesterol.

The impact of cholesterol exposure in early life on later cholesterol metabolism is not clearly understood. Sixteen newborn genetically lean and obese pigs were fed 0 or 5.0 g cholesterol/kg diet (0 or 0.5%) (liquid diets for 12 d, dry diets thereafter) for 33 d, after which they were all fed 10.0 g cholesterol/kg diet (1.0%) for 23 d. All animals were killed on d 56 and whole-body protein, fat and water were determined on the ground carcass. Dietary cholesterol had no consistent effect on growth rates or body composition. Mean fat content of lean pigs was 15.1% compared with 22.7% for obese pigs; corresponding values were 14.8 and 14.4% for protein and 65.5 and 58.3% for water. Concentrations of plasma total cholesterol, HDL cholesterol and apolipoproteins B and A-1 were increased by 0.5% dietary cholesterol in obese but not in lean piglets, although dietary cholesterol caused HDL and LDL size distribution profiles to shift toward larger-sized components in both strains. Plasma total cholesterol and apolipoprotein B concentrations rose two- to eightfold in all groups after the 1% cholesterol diet was consumed; these changes were accompanied by shifts in LDL and HDL size distribution profiles towards larger-sized components. With 1.0% cholesterol in the diet of all groups, HDL cholesterol concentration increased by approximately 50% in both groups of lean pigs and in obese pigs previously fed cholesterol, but did not increase further in obese pigs previously fed 0.5% cholesterol. The magnitude of the hypercholesterolemic response in lean pigs was blunted by previous exposure to 0.5% dietary cholesterol, but the response was accentuated in obese animals that had been previously exposed to 0.5% dietary cholesterol. These data provide evidence that genetic differences between obese and lean pigs affect their serum lipoprotein responses to high cholesterol intake.     

The protective effect of supplemental calcium on colonic permeability depends on a calcium phosphate-induced increase in luminal buffering capacity

An increased intestinal permeability is associated with several diseases. Previously, we have shown that dietary Ca decreases colonic permeability in rats. This might be explained by a calcium-phosphate-induced increase in luminal buffering capacity, which protects against an acidic pH due to microbial fermentation. Therefore, we investigated whether dietary phosphate is a co-player in the effect of Ca on permeability. Rats were fed a humanised low-Ca diet, or a similar diet supplemented with Ca and containing either high, medium or low phosphate concentrations. Chromium-EDTA was added as an inert dietary intestinal permeability marker. After dietary adaptation, short-chain fructo-oligosaccharides (scFOS) were added to all diets to stimulate fermentation, acidify the colonic contents and induce an increase in permeability. Dietary Ca prevented the scFOS-induced increase in intestinal permeability in rats fed medium- and high-phosphate diets but not in those fed the low-phosphate diet. This was associated with higher faecal water cytotoxicity and higher caecal lactate levels in the latter group. Moreover, food intake and body weight during scFOS supplementation were adversely affected by the low-phosphate diet. Importantly, luminal buffering capacity was higher in rats fed the medium- and high-phosphate diets compared with those fed the low-phosphate diet. The protective effect of dietary Ca on intestinal permeability is impaired if dietary phosphate is low. This is associated with a calcium phosphate-induced increase in luminal buffering capacity. Dragging phosphate into the colon and thereby increasing the colonic phosphate concentration is at least part of the mechanism behind the protective effect of Ca on intestinal permeability.     

Dietary ascorbic acid for neonatal pigs reared artificially

During the first 21 d of feeding a casein-glucose liquid diet the performance of pigs weaned at 1-3 d of age was not affected by ascorbic acid (AA) added at levels ranging from 165 to 990 ppm in two experiments. However, AA tended to improve growth rate from d 22 to 36 in experiments where pigs were fed a dry diet, but not when fed the diet in liquid form. The concentrations of AA in plasma, spleen and small intestinal tissues increased linearly with increasing dietary AA. No evidence of variability of AA concentration in adrenals was observed, whereas its content in the liver was increased only at 990 ppm AA. The AA concentrations in the small intestinal tissue increased progressively from the duodenum, jejunum to the ileum, mainly due to the increase in AA in the mucosal compared with the serosal layer. Dietary AA had no effect on the blood hematocrit, hemoglobin or on the concentrations of glucose or urea-N in plasma and protein in organs and intestinal tissues.     

The effect of wheat bran on the absorption and accumulation of cadmium in rats

1. The major purpose of the present study was to determine whether the addition of wheat bran to endosperm crisp bread in a composite diet given to rats for 6 weeks causes an increase in the accumulation of cadmium in the rats due to the Cd content in the bran, or whether binding factors in the bran, such as dietary fibre and phytic acid, reduce or prevent the accumulation of this Cd. A second purpose was to determine whether the accumulation of Cd can be estimated by measuring the absorption of 109Cd given in a single meal of the diet. 2. Three groups of eight rats were fed on one of three diets. Half of each diet consisted of a basal mixture of starch, protein, oil, minerals and vitamins. The remainder consisted of crisp breads based on refined wheat flour (endosperm group), wheat flour + bran in equal amounts (bran group) and wheat flour + Cd to give a Cd content similar to that of the bran group (endosperm + Cd group). After 41 d on the diets, the rats were deprived of food but not water for 12 h and then given a 5 g test meal of their respective diets with 109Cd added. After 3 h the remaining 109Cd-labelled diets were replaced with the unlabelled diets for 3 h before the rats were killed. 3. The total Cd contents in the wall of the proximal small intestine, including mucus, and in the liver and kidneys were highest in the endosperm + Cd group and lowest in the endosperm group.(ABSTRACT TRUNCATED AT 250 WORDS)     

The digestion of fibre by pigs. 3. Effects of the amount and type of fibre on physical characteristics of segments of the gastrointestinal tract

The aim of the study was to determine the relative effects of feeding growing pigs with graded amounts of neutral-detergent fibre (NDF) from various sources on the empty wet weight of segments of the pig gastrointestinal tract, on the weight and moisture content of their digesta, and on the pattern of digesta movement in them. Increased NDF intakes were associated with significantly higher wet weights of all gastrointestinal segments and increased lengths of the caecum. The lengths of both the small and the large intestines were unaffected by the ingestion by the pigs of different amounts of NDF from various sources. However, the caecum responded to these increased intakes of NDF by significant increases in length. The source of NDF in the diet was a factor that markedly influenced both the length and the weight of the distal colon. The nature of these increases in weight and length morphologically and their biological significance have not been determined. Despite some significant differences, neither the type nor the level of dietary NDF had any appreciable effect on the dry weight and on the proportion of dry matter (DM) of the contents in the contents in the stomach. As the level of NDF intake was increased, more undigested dietary material was found in all segments of the digestive tract of the pigs. The proportion of DM in the residues decreased progressively from the caecal contents to the contents of the distal colon. In most cases the degree to which the level of NDF intake affected the weight of the contents and the proportion of DM in them was highly dependent on the source of NDF in the diet. The distribution of the feed consumed in the morning and in the evening, as measured with stained feed particles and polyethylene beads, was extremely variable. It is concluded that prolonged intakes by pigs of diets containing high levels of fibre may lead to a hypertrophy and hence increased weight of segments of the gastrointestinal tract.     

Effects of a dietary oxidized fat on cholesterol in plasma and lipoproteins and the susceptibility of low-density lipoproteins to lipid peroxidation in guinea pigs fed diets with different concentrations of vitamins E and C

To investigate the effect of a dietary oxidized fat on the concentrations of cholesterol in liver, plasma, and lipoproteins and the susceptibility of low-density lipoproteins (LDL) to lipid peroxidation, and to explore the effects of vitamins E and C, male guinea pigs were divided into five groups. Four groups were fed diets with an oxidized fat supplemented with 35 or 175 mg alpha-tocopherol equivalents/kg and 300 or 1000 mg of vitamin C/kg for 29 days. One group, used as a control, was fed the same basal diet with fresh fat with 35 mg alpha-tocopherol equivalents/kg and 300 mg of vitamin C/kg. Guinea pigs fed the oxidized-fat diets, irrespective of dietary vitamin E and C concentrations, had significantly lower concentrations of total cholesterol in the liver and a lower concentration of cholesterol in LDL than the control animals fed the fresh fat. According to the lag time before onset of lipid peroxidation, LDL of guinea pigs fed the oxidized-fat diet with 35 mg alpha-tocopherol equivalents and 300 mg vitamin C/kg were significantly more susceptible to copper-induced lipid peroxidation than those of guinea pigs fed the fresh fat diet. Within the groups fed the oxidized fat diets, increasing the dietary vitamin E concentration from 35 to 175 mg/kg significantly (p < 0.05) and increasing the dietary vitamin C concentration from 300 to 1000 mg/kg in tendency (p < 0.10) reduced the susceptibility of LDL to oxidation. LDL of guinea pigs fed the oxidized fat diets with 175 mg alpha-tocopherol equivalents/kg were even more resistant to oxidation than LDL of guinea pigs fed the fresh diet. In conclusion, the study shows that dietary oxidized fat influences the cholesterol metabolism and the susceptibility of LDL to lipid peroxidation; the latter can be modified by dietary vitamins E and C.     

The degree of methylation influences the degradation of pectin in the intestinal tract of rats and in vitro

We investigated the degradation, metabolism, fate, and selected effects of pectin in the intestinal tract of rats. Conventional and germfree rats were fed for 3 wk diets containing 6.5% pectin (degree of methylation 34.5, 70.8 and 92.6%, respectively) or pectin-free diets. Pectin passes the small intestine as a macromolecule. The molecular weight distribution of pectins isolated from intestinal contents of germfree rats were unaffected by diet. No or very little galacturonan was found in cecum, colon or feces of most of the conventional rats. In colon contents of some conventional rats, di- and trigalacturonic acid were present. Total anaerobic and Bacteroides counts were greater in groups fed pectin. The concentration of short-chain fatty acids (SCFA) was higher in cecum and feces in all pectin-fed groups. With increasing degree of methylation, the formation rate of SCFA decreased in the cecum of conventional rats. During in vitro fermentation of pectin with fecal flora from rats, unsaturated oligogalacturonic acids appeared as intermediate products. Low-methoxyl pectin was fermented faster than high-methoxyl pectins in vivo and in vitro. Pectin-fed rats had greater ileum, cecum and colon weights. We conclude that structural parameters of pectin influence its microbial degradation in the intestinal tract.     

Tissue lipids and intestinal ATPases in rabbits fed cassava (Manihot uttilisima) and plantain (Musa paradisica) diets

The effect of two vegetable sources of dietary fiber (DF) from Africa, plantain and cassava, has been studied on lipid metabolism and intestinal ATPases in cholesterol-fed rabbits. In an eight-week experiment, it was shown that both sources of DF are capable of reducing serum cholesterol levels in rabbits by diverting cholesterol from the blood to the liver. The DF from plantain had more effect. When the rabbits were switched from test to control and back to the test diets only those on plantain diet maintained a steady state level of serum cholesterol. The other diets caused a drop in serum cholesterol levels in the absence of dietary cholesterol and a sharp rebound on the introduction of cholesterol-based diets. Cassava diet was hypertriglyceridimic at all times.

The ATPases were highly elevated in the ileum of rabbits fed the cassava diet and this was associated with the higher content of insoluble and particulate components of cassava which may cause cell sloughing and alteration in the morphology of the intestine. Also, because the available minerals will be distributed between those that will physically interact with DF and those to be transported, a rise in specific activity of the vectorial enzyme was stimulated to meet the challenge of competition for minerals.     

Effects of dietary fibre and tannins from apple pulp on the composition of faeces in rats.

The present study was undertaken to explore the effect of apple pulp on weight and composition of faeces. This material is rich in dietary fibre (DF; 620 g dry matter/kg) and contains appreciable amounts of polyphenols. Recent reports indicate that both condensed tannins (CT) and soluble polyphenols form cross-links with protein and inhibit digestive enzymes, affecting the protein digestibility, and may produce a stimulation of endogenous nitrogen excretion. Two groups of male Wistar rats were fed on either a control diet free of DF or a diet containing 100 g apple pulp DF/kg during 7 d after a 4 d adaptation period. Body-weight and food intake were monitored daily and faeces and urine were collected once daily. DF, water content and polyphenolic compounds were measured in faeces, and N content in both faeces and urine. Faecal weight increased in the fibre group by 280 and 240% when compared with wet and dry faecal weights of animals fed on the fibre-free diet. Soluble dietary fibre (SDF) excreted in faeces was 10.9% of the SDF ingested, which suggested a low resistance to fermentation of this fraction. Of the insoluble DF, 43% of the ingested fibre was fermented. Polyphenols were degraded in the intestinal tract. Of the ingested CT, 68.6% was recovered in faeces, while the soluble polyphenols were extensively degraded (85.7% of that ingested). On the other hand, a higher faecal N excretion was observed for the fibre-fed group, suggesting a decrease in the digestibility of the dietary protein and lower apparent digestibility of the dietary protein and lower apparent digestibility and N balance indices.