Breakdown of plant carbohydrates in the digestive tract of pigs fed on wheat‐ or oat‐based rolls

Cell wall materials from various cellular tissues of cereals may potentially influence the digestion and absorption processes in different ways. The objective of the present investigation was to study the breakdown of plant carbohydrates in the gastrointestinal tract of pigs fed a low‐fibre (LF; 65 g kg⁻¹ dry matter) wheat flour‐based diet and two high‐fibre diets with added insoluble fibre from wheat bran (HFWB; 112 g kg⁻¹ dry matter) or soluble fibre from oat bran (HFOB; 108 g kg⁻¹ dry matter). The diets were formulated to provide ∼0.31 energy from fat, ∼0.18 energy from protein and ∼0.51 energy from carbohydrates and were offered as baked rolls to eight ileum‐cannulated hypercholesterolemic pigs in a crossover design. Carbohydrates were the predominant ileal constituent, with most of the carbohydrates present as non‐starch polysaccharides (NSP). Starch in all diets was almost completely digested at this site of the gastrointestinal tract, with digestibility values above 0.99. The ingested amount of NSP was quantitatively recovered in ileal materials with the wheat‐based diets, while there was a significant loss of 0.27 of NSP primarily as mixed linked (1→3)(1→4)‐‐D ‐glucan with diet HFOB. The concentration and flow of lactic acid were also highest in the ileum after feeding diet HFOB, indicating that ‐glucan stimulated lactic acid formation. Any soluble components that reached the large intestine were almost completely broken down, while the digestibility of insoluble NSP constituents was significantly lower for diets LF and HFWB than for diet HFOB. The high degradation of oat bran resulted in a lower effect on faecal dry and wet bulking than was found with wheat bran. In conclusion, cereal starch was practically completely degraded in the small intestine, while the site and extent of NSP degradation, lactic acid formation and bulking properties were influenced by the fibre source. © 2000 Society of Chemical Industry     

Integration of ileum cannulated pigs and in vitro fermentation to quantify the effect of diet composition on the amount of short‐chain fatty acids available from fermentation in the large intestine

Using cannulated pigs and a standardised in vitro fermentation system the effect of diet and non‐starch polysaccharides (NSP) on the amount of energy available from microbial fermentation in the large intestine could be predicted. The available energy was calculated from the amounts of short‐chain fatty acids (SCFA) produced. Three diets were investigated: a low fibre diet based essentially on wheat flour (56 g NSP kg⁻¹ feed) and two high fibre diets with added oat bran (93 g NSP kg⁻¹ feed) or wheat bran (102 g NSP kg⁻¹ feed). Colonic fermentation was estimated by in vitro fermentation of freeze‐dried ileal effluent collected from cannulated pigs. The in vitro fermentation method was optimised to use 10 g ileum content litre⁻¹ incubated at pH 6.0 in a fermentor containing faecal slurry consisting of anaerobic mineral salts medium and 50 g litre ⁻¹ faeces from pigs fed the same diets as the cannulated pigs. The results demonstrate that it is very important to compensate for the faecal SCFA contribution when calculating the amount of SCFA produced from ileal digesta during in vitro fermentation. The amount of NSP digested in vitro was compared with data obtained from in vivo studies and there was a good agreement between in vivo and in vitro data. We concluded that the integrated in vivo–in vitro method is a valuable technique to estimate the effect of diet and NSP on the amount of SCFA produced in the large intestine and when fed the three diets the microbial fermentation in the large intestine provided between 2.4–6.4% of the total available energy. © 1999 Society of Chemical Industry     

Faecal Composition and Nitrogen Excretion of Rats Fed on Diets Containing Sweet Lupin (Lupinus angustifoliusL) or its Fractions

Five N balance studies were conducted to determine the faecal composition and N excretion of feeding raw Lupinus angustifolius seed meal and its fractions for growing rats using a semi-synthetic lactalbumin-based diet as control. Diets were formulated to have equal amounts of energy. The protein was incorporated at the level of 10% bulk and contained unsupplemented lupin seed meal (LMU) and fully supplemented lupin seed meal (LMFS) at 360 g kg⁻¹ diet, aqueous extract non-dialysed (LPAND) at 196 g kg⁻¹ aqueous extract dialysed soluble at pH 7·0 (LPAD) at 148 g kg⁻¹ aqueous extract dialysed insoluble at pH 7·0 (LPADI) at 124 g kg⁻¹, buffer dialysed soluble at pH 7·0 (BUSOL) at 136 g kg⁻¹, buffer dialysed insoluble at pH 7·0 (BUDI) at 119 g kg⁻¹ and lupin meal residue after aqueous and buffer extraction (LMR) at 170 g kg⁻¹ diet. Rats were pair-fed for 10 days with all the above diets which had been supplemented with essential amino acids up to the target requirements for rats. Faecal wet and dry weight were increased in rats fed on LMU, LMPS and LMR diets compared to those obtained from the control diet based on lactalbumin (milk protein) LACT. The higher faecal weight was largely due to water content. The higher faecal N excretion observed in LMU, LMFS, LPAND, LPAD, BUSOL, BUDI and LMR compared to that of LACT diet was significantly lower and thus which was assumed not to be due to a decrease in the digestibility of the dietary protein, which was over 90% as compared to that in the control group. Analysis suggested that an increase in endogenous N excretion is involved in the rise of its excretion in the faeces, and indicates a long-term effect of this seed as a protein and or fibre source in monogastrics.     

Nutritional value of feed grade chickpeas for ruminants and pigs

The feeding value of feed grade chickpeas (Kabuli and Desi type) for ruminants and pigs was determined in two studies. Two ruminally fistulated cows were used in the first study to determine the effects of moist heat treatment (127 °C for 10 min) on the ruminal protein degradability of feed grade chickpeas. Heat treatment reduced (P < 0.05) soluble crude protein and increased (P < 0.05) the amount of crude protein associated with neutral detergent fibre for both types of chickpeas. Ruminal degradability of crude protein for Kabuli and Desi chickpeas was reduced by 39 and 33% (P < 0.05) respectively as a result of heating. In the second study, 64 crossbred pigs were each assigned to one of four dietary treatments in a factorial (4 treatments × 2 sexes) design experiment. The experimental barley/wheat‐based diets were supplemented with either soybean meal (control), Kabuli chickpeas (300 g kg⁻¹), Desi chickpeas (300 g kg⁻¹) or field peas (300 g kg⁻¹). Dry matter and gross energy digestibility coefficients, determined using the indicator method, were lower (P < 0.05) for the Desi‐ than for the Kabuli‐supplemented diet. However, no differences were observed in dry matter or gross energy digestibility between the Kabuli chickpea‐supplemented diet and the control or the field pea‐supplemented diet. Diets supplemented with chickpeas or field peas had a lower (P < 0.05) crude protein digestibility than the control diet. Pigs fed either of the chickpea‐supplemented diets during the growing phase gained less (P < 0.05) than pigs fed the control diet. However, during the finishing phase and over the entire experiment, dietary treatment had no effect on pig performance. There were no significant differences in carcass traits between pigs fed any of the four diets. It was concluded that moist heat treatment is an effective method to increase the rumen escape protein value of chickpeas and that the inclusion of feed grade Kabuli or Desi chickpeas in finishing diets up 300 g kg⁻¹ had no detrimental effects on pig performance. © 2000 Society of Chemical Industry     

Dietary fibre level and enzyme inclusion affect nutrient digestibility and excreta characteristics in grower pigs

An experiment was conducted with 12 grower pigs to determine the effects of (1) manipulating dietary neutral detergent fibre (NDF) level and (2) dietary inclusion of fibre‐degrading enzymes on nutrient digestibility and excreta characteristics in pigs. Four diets were formulated to contain three levels of NDF: 1, 66 g kg^?1 NDF (low fibre); 2, 121 g kg^?1 NDF (moderate fibre); 3, 222 g kg^?1 NDF (high fibre); 4, diet 3 plus 2.0 g kg^?1 enzyme. Increasing levels of dietary NDF linearly decreased dry matter and energy digestibilities (r² = 0.99, P < 0.05). Lowering dietary NDF from 222 to 121 g kg^?1 improved nitrogen digestibility by 13% (P < 0.01). Faecal production was decreased by 9% for each 1% decrease in dietary NDF content (r² = 0.99, P < 0.05). Inclusion of fibre‐degrading enzymes in the high‐fibre diet improved dry matter and energy digestibilities by 2 and 3% respectively, and reduced faecal production by 10% (P < 0.01). Faecal and manure (faeces plus urine) pH values from pigs fed the high‐fibre diet and the high‐fibre plus enzyme diet were lower than those from pigs fed the other experimental diets (P < 0.05). In conclusion, lowering the dietary NDF level or inclusion of fibre‐degrading enzymes in high‐fibre diets may offer relatively practical and easy methods for reducing waste production in pigs. © 2002 Society of Chemical Industry     

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.     

The influence of fibre level and fat supplementation in expander‐processed diets on grower–finisher pig performance

Seventy‐two entire male pigs (40.4 ± 1.0 kg) were used to study the effects of increasing crude fibre (CF) level in the diet and maintaining the digestible energy (DE) content of the diet by increasing dietary fat inclusion on pig performance and nutrient digestibility in a 3 × 2 factorial experiment. Productive performance and nutrient digestibility were determined in individually fed pigs offered expander‐processed pelleted diets ad libitum containing three levels of CF (50, 60 and 70 g kg^?1) and two levels of fat supplementation (25 and 50 g kg^?1) until slaughter at 100 kg. All diets were expander processed at 105 °C for 5 s at 35 bar pressure having been previously conditioned at 85 °C for 5 s. All diets were formulated to have similar concentrations of digestible energy (13.5 MJ kg^?1) and lysine (10 g kg^?1) and the fat source was a 60:40 blend of tallow and palm oil. The increase in dietary CF level decreased (P < 0.05) the apparent digestibility of crude protein, organic matter (OM) and energy, while the inclusion of 50 g kg^?1 fat decreased (P < 0.01) OM and energy digestibility. The inclusion of 50 g kg^?1 fat in the diet increased (P < 0.01) ether extract digestibility at the 50 and 60 g kg^?1 CF levels; however, fat inclusion had no effect at the 70 g kg^?1 CF level. There was no CF × fat interaction in any growth criteria. The inclusion of 50 g kg^?1 fat in the diet significantly reduced (P < 0.05) feed intake (2.28 versus 2.43 kg day^?1, SEM 0.039), average daily gain (ADG; 0.877 versus 0.927 kg day^?1, SEM 0.017) and DE conversion ratio (36.1 versus 35.0 MJ kg^?1, SEM 0.40). The increase in dietary CF level decreased (linear, P < 0.05) feed intake (2.45 versus 2.32 versus 2.29 kg day^?1, SEM 0.040), ADG (0.940 versus 0.896 versus 0.872 kg day^?1, SEM 0.021) and kill‐out proportion (740 versus 741 versus 730 g kg^?1, SEM 3.6). In conclusion, increasing both the CF level and supplementary fat inclusion rate had a negative effect on pig growth performance and nutrient digestibility. © 2002 Society of Chemical Industry     

Glycemic Index and Chemical Composition of Traditional Omani Breads

This study evaluated the chemical composition and glycemic index (GI) of eight different types of traditional Omani breads made from wheat flour. Significant (P < 0.05) differences were observed in the proximate chemical composition, dietary fibre content, and gross energy value of these breads. The moisture, crude protein, total fat, ash, crude fibre and nitrogen free extract (NFE) contents ranged between 21.6–51.6, 4.3–10.5, 0.8–13.8, 1.2–2.3, 1.0–2.0, and 34.5–61.8 g/100 g of sample respectively. The values for dietary fibre were between 5.6, 9.6 g/100g, and the gross energy contents ranged between 897 and 1468 kJ/100 g. The GI value of these breads also differed significantly (P < 0.05). No significant differences were however observed among the GI values for White Toast Bread (local commercial bread), Brown Toast Bread (local commercial bread), White Khubz Lebanani (local commercial bread), Brown Khubz Lebanani (local commercial bread), and Chapati (local homemade bread), which were 63 ± 12, 58 ± 15, 63 ± 10, 57 ± 20, and 58 ± 10, respectively. Paratha (local restaurant made bread with fat), Goleh (local homemade soft bread), and Rekhal (local homemade thin bread) showed significantly (P < 0.05) lower GI values as compared to other breads, and these were 32 ± 13, 43 ± 13 and 39 ± 7, respectively. No specific correlation was observed in the chemical composition and glycemic index of these breads. These breads fall within low to medium GI category of foods.     

Mucilage in linseed: effects on the intestinal viscosity and nutrient digestion in broiler chicks

A study was conducted to obtain more information on the role of mucilage in the adverse effects produced by the use of linseed in chick diets. Mucilaginous material was extracted from linseed with hot distilled water (80 °C) for 2 h; after filtration the water‐soluble extract was freeze‐dried and ground. A maize/soyabean meal basal diet with supplemental linseed mucilage extract (0, 4, 8, 12 and 16 g kg^?1) was given to chicks from 8 to 28 days of age. During the last 3 days the excreta were collected quantitatively, then the chicks were slaughtered and the jejunal and ileal contents were collected. Feeding the mucilage extract‐containing diets to birds increased markedly, from 4.35 to 18.89 mPa s, the digesta viscosity at jejunal level. The apparent faecal digestibility of crude fat and major fatty acids and the dietary AMEn value (metabolisable energy corrected to zero nitrogen retention by the body) were linear and negatively influenced by the inclusion level of mucilage extract. However, the presence of mucilage in the diet did not affect the apparent ileal digestibility of crude protein and individual amino acids. These results seem to suggest that mucilage in linseed has lower antinutritional properties than those reported for whole linseed or linseed meal when included in chick diets. © 2002 Society of Chemical Industry     

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     

Chemical composition,digestibility and protein quality of 12 sunflower (Helianthus annuus L) cultivars

Twelve sunflower (Helianthus annuus L) cultivars grown in Spain were analysed and tested in experiments with rats. The dehulled seeds contained an average of 32.2 MJ kg⁻¹ dry matter (DM) gross energy, 653 g kg⁻¹ DM fat, 60 g kg⁻¹ DM total non-starch polysaccharides (NSP) and 6 g kg⁻¹ DM Klason lignin. The sunflower seed hulls contained 20.2 MJ kg⁻¹ DM gross energy, 53 g kg⁻¹ DM fat, 562 g kg⁻¹ DM total NSPs and 239 g kg⁻¹ DM Klason lignin. The sunflower samples were dehulled and partially defatted (to ∼17% fat) and included in diets for rats. The dehulled, partially defatted samples contained on average 74.6 g nitrogen kg⁻¹ DM and 1.409 mg g⁻¹ phenolic compounds (chlorogenic acid + caffeic acid + derivative 1 + derivative 2) varying from 0.677 to 2.847 mg g⁻¹. Groups of five growing rats were fed diets (9.38% crude protein) containing one of the sunflower cultivars as the only source of protein. Apparent ileal and faecal digestibilities were determined by using an indigestible marker (Cr₂O₃) and faecal digestibility based on total faecal collections. Apparent ileal, caecal and faecal digestibilities of organic matter were 81.2–91.5% (P = 0.05), 95.8–97.1% (P = 0.005) and 94.7–95.3% (P = 0.94) respectively. The apparent faecal digestibilities of DM, energy and protein (N × 6.25) were 93.2–93.8%, 93.5–94.3% and 81.6–84.3% respectively with no differences among cultivars. Biological value (BV) ranged between 63.8 and 73.2% (P = 0.0001) and net protein utilisation (NPU) between 59.9 and 69.5% (P = 0.0001). BV and NPU were positively correlated with lysine and threonine contents, but no correlation with the analysed phenolic compounds was detected. © 1999 Society of Chemical Industry     

Response of nutrient digestibilities to feeding diets with low and high levels of soybean trypsin inhibitors in growing pigs

Studies were carried out to determine the effect of dietary soybean trypsin inhibitor (SBTI) content on nutrient and energy digestibilities in growing pigs. Six barrows, average initial body weight (BW) 47·8±4·0 kg, were fitted with a simple T-cannula at the distal ileum and fed two diets according to a crossover design. Two maize starch-based diets were formulated to contain 200 g crude protein (CP) kg⁻¹ from either Nutrisoy (a food-grade defatted soy flour) or autoclaved Nutrisoy. The contents of SBTI in the Nutrisoy and autoclaved Nutrisoy diets were 13·4 and 3·0 g kg⁻¹, respectively. The experiment consisted of two periods of 12 days each. The average BW at the start of the first and second experimental periods were 53·3±3·7 and 61·0±5·1 kg, respectively. The average BW at the conclusion of the experiment was 71·8±7·6 kg. The ileal digestibilities of dry matter (DM), organic (OM), energy, CP and all amino acids measured were higher (P<0·01) in pigs fed the autoclaved Nutrisoy diet. The energy digestibility increased from 66·0 to 77·9%, and the CP digestibility increased from 37·4 to 77·1%. The increases in ileal digestibilities of the indispensable amino acids ranged from 27·0 (methionine) to 49·2 (leucine) percentage units. The increases in ileal digestibilities of the dispensable amino acids ranged from 30·2 (aspartic acid) to 50·8 (tyrosine) percentage units. The faecal digestibilities of all criteria measured were also higher (P<0·01) in pigs fed the autoclaved Nutrisoy diet. Furthermore, there was a greater (P<0·01) net disappearance (g kg⁻¹ DM intake) of DM, OM, CP, energy and all amino acids in the large intestine of pigs fed the Nutrisoy diet. In conclusion, feeding diets containing high levels of SBTI decreased both ileal and faecal digestibilities of all criteria measured. The formation of SBTI-enzyme complexes is likely to be responsible for the reduction in protein digestion and amino acid absorption. © 1998 SCI.     

Effects of wheat and rye bread structure on mastication process and bolus properties

Chemical composition, baking process and structure of breads influence their degradation in digestion leading to different postprandial responses. Rye bread has a very different structure as compared to wheat bread, and rye breads are known to induce lower postprandial insulin responses than wheat bread. The aim of this study was to find out potential differences in mastication and initial starch hydrolysis rate of rye and wheat breads. Three rye breads (wholemeal rye, endosperm rye and endosperm rye with gluten) and wheat bread were masticated by fifteen participants and the process was monitored using electromyography. The particle size distribution and initial in vitro starch hydrolysis of the bread boluses were analysed. Specific volume correlated negatively and closed porosity of breads correlated positively with work required for mastication. When compared to wheat bread, wholemeal rye bread required more work for mastication process (p = 0.004). Rye breads were degraded to smaller particles than wheat bread during mastication. There was a trend (p = 0.098) towards slower in vitro starch hydrolysis rate in rye bread boluses than in wheat bread boluses. The results indicate that the digestion process of rye breads differs from that of wheat bread already in the early phase of digestion. This may be one reason behind the unique postprandial responses reported for rye breads.     

Nutrient digestibility,performance and carcass traits of growing–finishing pigs fed diets containing graded levels of dehydrated lucerne meal

BACKGROUND: Plant breeders have attempted to improve the nutritonal value of lucerne (alfalfa) by selecting for higher protein and lower fibre concentrations. Although targeted at ruminants, such changes could also improve the nutritional value of lucerne for monogastrics. The objective of this study was to determine the effects of graded levels of dehydrated lucerne meal on nutrient digestibility, performance and carcass traits of swine. RESULTS: The digestibility of dry matter, protein and energy declined linearly (P < 0.05) as the level of lucerne meal in the diet increased. Including lucerne meal at levels greater than 75 g kg^?1 was detrimental to the growth rate of pigs during the growing period. During the finishing period, inclusion of lucerne meal at 75 and 150 g kg^?1 resulted in improvements in weight gain and feed intake. Carcass traits were generally unaffected by lucerne inclusion. CONCLUSION: Lucerne meal may have greater potential for inclusion in diets fed to growing–finishing pigs than previously realized. To maximize pig performance, lucerne meal should be limited to less than 75 g kg^?1 diet during the growing period, while it is possible to go as high as 150 g kg^?1 diet during the finishing period without detrimental effects on performance. Copyright © 2008 Society of Chemical Industry     

Some effects of fibre and starch on the determination of protein quality

An assessment was carried out of the effects of an increase in the amount of fibre, as cellulose, and of a replacement of maize starch by potato starch in diets containing egg albumen as the sole protein, on the determination of true digestibility (TD) and biological value (BV). An increase in the fibre content of the diet at the expense of maize starch led to a rise in both fascal and urinary N excretion, with diets containing either 20 or 80 g egg albumen kg^?1. However, the response of the rats to increasing fibre concentration in the diet was different for the two levels of protein probably due to differences in dry matter intake (DMI). It was found that the conventional method of estimating metabolic faecal nitrogen (MFN) was not adequate for diets of decreasing digestibility; TD decreased by 0.35% for a rise of 1% cellulose in the diet. A more accurate method of estimating MFN was derived from a relationship between the N in the faeces and the digestibility of the diet. The increase in urinary N excretion led to a decrease of 0.41% in BV for a 1% rise in the cellulose concentration of the diet. It appears, therefore, that the ratio of digestible to indigestible matter in the diet affects the determination of protein quality. The replacement of maize starch by potato starch in the diet caused an increase in faecal N excretion and a decrease in urinary N excretion until a level of 200 g potato starch kg^-1 was reached. This affected the determination of TD and BV accordingly. An increase in the size of the caecum of the rats fed potato starch indicated that increased fermentation may have resulted in production of additional bacterial cells to be excreted in the faeces. Thus, both the amount of fibre and the type of starch in the diet affect the determination of protein quality.     

A study of the need for fibre by the growing New Zealand white rabbit

New Zealand White rabbits, aged between 5 and 8 weeks, were offered diets based on oatmeal together with up to 500 g kg^?1 of ground oat husk, or 500 g kg^?1 of ground barley straw or 400 g of a purified cellulose. The rabbits gained about 40 g liveweight per day when fed a well-balanced control diet (in which oatmeal, grassmeal, corn oil and fishmeal were the main constituents) and, apart from one occasion, there was no significant reduction in this rate of gain even when the diets offered contained up to 500 g kg^?1 of these fibre sources. Food consumption increased from 80 g day^?1 to 115 g day^?1 as the acid detergent fibre concentration in the diet increased from 39 to 270 g kg^?1. Digestible and metabolisable energy contents of the diets fell as the fibre concentration rose but the rabbits were able to adjust their intakes and maintain their daily metabolisable energy intakes constant at about 1100 kJ. The proportion of fat in the body dry matter fell as the fibre concentration in the diet was raised. A minimum dietary fibre content of 100 g kg^?1 as measured by the acid detergent fibre or crude fibre techniques is suggested for optimum healthy growth.     

Acrylamide–asparagine relationship in baked/toasted wheat and rye breads

Acrylamide in baked and toasted wheat and rye bread was studied in relation to levels of asparagine in flour, dough, bread and toasts. Asparagine was consumed during bread preparation resulting in reduced acrylamide content in the products. In wheat bread, 12% of the asparagine initially present in the flour (0.14 g kg^?1) remained after yeast fermentation and baking; for rye bread, 82% of asparagine remained after sourdough fermentation and baking. Asparagine present in untoasted wheat bread had totally reacted after hard toasting. Toasted wheat and rye bread slices contained 11–161 and 27–205 µg kg^?1 acrylamide, respectively, compared to untoasted wheat and rye bread with <5 and 7–23 µg kg^?1 acrylamide, respectively. The dietary intake of acrylamide from bread (untoasted) of 2 µg day^?1 is relatively low; however, acrylamide exposure from bread increases several fold for people eating toasted bread.     

In vitro biohydrogenation and total tract digestibility of oleamide by sheep

Disappearance of cis-18:1(n-9) from ruminal in vitro cultures supplemented with either oleic acid or oleamide was measured over 48 h to determine if the amide resisted biohydrogenation. Oleamide added to the substrate maintained higher concentrations of cis-18: 1(n-9) in the microbial cultures at 24 and 48 h of incubation compared to substrates with added oleic acid. Disappearance rates of cis-18: 1(n-9) from the cultures, which were calculated as a measure of biohydrogenation, were 0·064 and 0·025 h⁻¹ for the oleic acid and oleamide supplements, respectively. Four sheep were fed four diets (control, 42 g kg⁻¹ oleic acid, 23 g kg⁻¹ oleamide, and 45 g kg⁻¹ oleamide) in a 4×4 Latin square to determine how the amide affected fatty acid digestibility. Total tract digestibilities of protein and fibre were not affected (P>0·05) by either oleic acid or oleamide compared to the control diet. Fatty acid and energy digestibilities were not changed (P>0·05) by oleic acid, but were increased (P<0·05) when oleamide was added to the sheep diets at 45 g kg⁻¹. These results show that oleamide resists ruminal biohydrogenation without impairing fatty acid digestibility. © 1998 SCI.     

Observations on the determination of protein quality by the Thomas–Mitchell method

In the Thomas–Mitchell method for the assessment of protein quality, metabolic faecal nitrogen (MFN) and endogenous urinary nitrogen (EUN) are used to adjust faecal and urinary N excretion on test diets so that true digestibility (TD) and biological value (BV) can be calculated. Using an experimental technique where the urine and faeces from young growing rats were collected every 2 days for an experimental period of 28 days, trends in the estimation of MFN and in the determination of TD and BV were examined. A diet containing 20 g egg albumen kg^?1 on an as fed basis (2.85 g N kg^?1 dry matter) has previously been found to be most applicable for the estimation of EUN. This diet was also found to be appropriate for the estimation of MFN. To examine the effect of a change from an ad libitum intake of a stock diet (containing 150 g protein kg^?1) to the restricted intake of a test diet (containing 80–100 g protein kg^?1) on the determination of TD and BV, three protein sources (egg albumen, casein+1% L -methionine and soya bean meal) were fed at two levels of intake: 9 and 15 g day^?1. The time taken for the faecal N excretion to stablilise was very similar with all diets at both levels of intake. The TD of all three protein sources at both levels of intake increased gradually with increasing lengths of preliminary period. However, this increase was not great, and had little effect on the determination of the BV. Stabilisation of urinary N excretion with the three diets depended on the quality of the protein and the amount fed. This led to variation in BV with lengthening preliminary periods, especially at the lower level of intake. Urinary N excretion, and consequently BV, stabilised most rapidly with the highest quality protein (egg albumen) at the highest level of intake. However, stabilisation of BV with the lowest quality protein (soya bean meal) did not occur until after a preliminary period of 12 days, even at 15 g day^?1. This preliminary period is considerably longer than that usually employed, and thus it appears that for many proteins the BV may have been assessed during a period before N retention has fully stabilised.