Processing of maize germ oil cake into edible food grade meal and evaluation of its protein quality.

The commercial oil cake produced during expeller pressing of maize germ, was extracted with n-hexane and 80 percent ethanol followed by seiving to remove undesirable materials. In defatted maize germ oil cake (DMGOC): protein, starch, fat, crude fiber (CF) and ash were respectively 24.69, 36.55, 5.68, 7.56 and 3.90 percent and they decrease after processing except ash, which increased slightly. It contains better quality protein having only 3 percent zein and 47 percent albumin. Its amino acids like lysine and tryptophan and biological value (BV) were higher than that of whole maize grain, and was comparable with that of the amino acid requirement of preschool children and casein diets both. Its digestible energy (DE) was lower compared with whole maize grain as well as the casein diets. After processing albumin, globulin and zein decreased whereas glutelin and the residual fraction increased. Not much differences were observed in chemical composition and different amino acids, in vitro protein digestibility (IVPD), true digestibility (TD), BV and DE improved after processing.

Enhanced methionine levels and increased nutritive value of seeds of transgenic lupins (Lupinus angustifolius L.) expressing a sunflower seed albumin gene.

With the aim of improving the nutritive value of an important grain legume crop, a chimeric gene specifying seed-specific expression of a sulfur-rich, sunflower seed albumin was stably transformed into narrow-leafed lupin (Lupinus angustifolius L.). Sunflower seed albumin accounted for 5% of extractable seed protein in a line containing a single tandem insertion of the transferred DNA. The transgenic seeds contained less sulfate and more total amino acid sulfur than the nontransgenic parent line. This was associated with a 94% increase in methionine content and a 12% reduction in cysteine content. There was no statistically significant change in other amino acids or in total nitrogen or total sulfur contents of the seeds. In feeding trials with rats, the transgenic seeds gave statistically significant increases in live weight gain, true protein digestibility, biological value, and net protein utilization, compared with wild-type seeds. These findings demonstrate the feasibility of using genetic engineering to improve the nutritive value of grain crops.

The energy value of short-chain fatty acids infused into the caecum of pigs.

The present work was undertaken to study the energy value of a mixture of acetic, propionic and butyric acids (0.682:0.226:0.092) infused intracaecally in growing pigs. A basal diet low in fibre (42 g NSP/kg DM) was given at below the requirement for maximum weight gain. In six 2-week periods, N and energy balance measurements in eight growing pigs were carried out with and without infusion of short-chain fatty acids (SCFA). Heat production was measured using open-circuit chambers and the concentration of SCFA in faeces was determined. Less than 1% of the infused SCFA was excreted in faeces illustrating the capacity of the hind-gut to absorb and metabolize SCFA. Infusion of SCFA did not affect the digestibility of nutrients and energy. However, N retention increased demonstrating that SCFA are an energy source for protein gain when pigs are fed at below the requirement of energy. Increased CH4 production together with an increased excretion of branched-chain fatty acids in faeces suggested that there was a higher microbial activity in the hind-gut during infusion. The partial utilization of the infused energy in SCFA was 0.821. A small proportion of the infused energy in SCFA was retained in protein (0.099) and a considerable amount was retained as fat (0.722).

Energy expenditure and quantitative oxidation of nutrients in rats (Rattus norvegicus) kept in different thermal environments and given two levels of dietary fiber.

A study was performed to investigate the effect of environmental temperature (16 degrees C, 24 degrees C or 32 degrees C) and dietary fiber (DF) on energy expenditure and quantitative oxidation of nutrients in rats. Forty-eight male rats, initial body weight 90-105 g, were allocated to eight groups in two series. The rats kept at 24 degrees C was repeated in both series. Low and high fiber diets (56 vs. 257 g DF/kg dry matter) were studied in 6-week balance experiments. The rats in all groups were offered the same amount of air-dried food. Indirect calorimetry was used to measure the energy metabolism. The difference in heat production (HP) calculated by RQ and CN methods was < 2% and was not affected by environmental temperature and DF. The relation between fat and protein oxidation changed from 1.54 to 1.00 when the ambient temperature changed from 16 degrees C to 32 degrees C. The contribution of carbohydrate oxidation to total HP was lowest at 16 degrees C, whereas the fat and protein oxidation was highest at 16 degrees C. The oxidation of nutrients was not influenced by DF. The additional energy retained at the higher temperatures had a constant ratio between fat and protein, i.e., 70:30. At an energy retention of 65.8 kJ/kg0.75 d or less, body fat is mobilized and only protein deposited. Because of higher HP, rats living in the cold environment used more fat as substrate for HP than rats kept in warmer environments. The cold environment results in an increase in the amount of interscapular brown adipose tissue, but no significant difference was found between DF levels.

Energy values of non-starch polysaccharides: comparative studies in humans and rats.

Energy values of non-starch polysaccharides (NSP) were estimated from NSP fermentability and from digestible energy balances in human subjects and in rats. During four studies, humans consumed four low fiber control diets and six high fiber diets. For the rat diets, duplicates of the foods consumed by humans were mixed together, freeze-dried and ground. Calculated from fermentability, partial digestible energy values of NSP in humans and rats, respectively, were 8.2 +/- 1.3 and 5.7 +/- 1.2 (P = 0.0013, fruits and vegetables), 11.4 +/- 0.7 and 5.7 +/- 3.2 (P = 0.0001, citrus fiber), 5.0 +/- 2.1 and 2.2 +/- 3.3 (P = 0.0429, barley fiber at high protein intake), 4.4 +/- 1.8 and 2.4 +/- 2.0 (P = 0.0561, barley fiber at low protein intake), 6.7 +/- 1.4 and 7.6 +/- 1.2 (P = 0.296, coarse whole meal rye bread), and 7.1 +/- 0.6 and 6.1 +/- 1.7 (P = 0.157, fine whole meal rye bread) kJ/g NSP. Calculated from energy balances, partial digestible energy values of NSP in humans and rats, respectively, were 2.1 +/- 3.5 and -5.0 +/- 4.0 (P = 0.026, fruits and vegetables), 10.7 +/- 5.1 and 1.4 +/- 5.6 (P = 0.003, citrus fiber), 1.6 +/- 5.1 and -17.8 +/- 8.6 (P = 0.0001, barley fiber at high protein intake), -2.6 +/- 4.9 and -9.3 +/- 8.2 (P = 0.044, barley fiber at low protein intake), -3.0 +/- 7.0 and 0.9 +/- 2.5 (P = 0.27, coarse whole meal rye bread), and 0.9 +/- 5.1 and 0.6 +/- 3.7 (P = 0.89, fine whole meal rye bread) kJ/g NSP. Net energy values were 70% of digestible energy values. Differences between species were significant for NSP in fruits and vegetables, citrus fiber, and barley fiber at high protein intake. Most energy values calculated from energy balances were significantly lower than values calculated from NSP fermentation, with differences being greater in rats than in humans. Thus, the energy values of some types of NSP contained in mixed diets could not be estimated accurately from NSP fermentability either in humans or rats. In addition, our results suggest that the rat is not always a suitable model of humans for predicting energy values of NSP in mixed diets.

Energy metabolism and protein balance in growing rats housed in 18 degree C or 28 degree C environments and fed different levels of dietary protein.

A study was performed to investigate the effect of environmental temperature and increasing levels of protein in the diet on visceral organ size, digestibility, protein balance and energy metabolism in rats. Thirty-six male Wistar rats, initial body weight 77-80 g, were used in a factorial design consisting of three levels of dietary protein and two environmental temperatures of either 18 or 28 degrees C. Three fish meal-based diets were prepared to contain 91, 171 and 262 g protein (N X 6.25/kg diet). Gas-exchange measurements were made and urine and feces were quantitatively collected. The weights of the visceral organs from rats housed at 18 degrees C were greater (P < 0.05) than those of rats housed at 28 degrees C. The digestibilities of dry matter and protein were not affected by environmental temperature, whereas fat and energy digestibilities were higher (P < 0.05) at 18 degrees C than at 28 degrees C. As the level of protein was increased, the digestibilities of protein, energy and fat increased (P < 0.05). Protein intake and protein retention were higher at 18 degrees C (P < 0.05) than at 28 degrees C and increased (P < 0.05) as dietary protein concentration increased. Apparent biological value was lower (P < 0.05) at 18 degrees C than at 28 degrees C and decreased (P < 0.05) as dietary protein level increased. Heat production as a percentage of metabolizable energy was higher (P < 0.05) for the low protein diet than for the medium and high protein diets. The efficiency of energy utilization was depressed (P < 0.05) for the high protein diet when rats were kept at 28 degrees C. The results suggest that thermogenesis was induced when low protein was fed. The increase in thermogenesis may have been important in regulating energy balance and maintaining a constant body temperature in a cold environment.

The influence of dietary fibre and environmental temperature on the development of the gastrointestinal tract, digestibility, degree of fermentation in the hind-gut and energy metabolism in pigs.

The present study was undertaken to provide detailed information about the effect of dietary fibre (DF) level on the development of the digestive tract, on nutrient digestibility and on energy and protein metabolism of pigs housed in low (13 degrees) or high (23 degrees) thermal environments. Low- and high-fibre diets (59 v. 268 g DF/kg DM) were studied in three balance periods with fistulated pigs in the weight range 45-120 kg. Heat production was measured using open-circuit respiration chambers. Pea fibre and pectin were used to adjust the DF level in the high-fibre diet. Per kg empty body weight the stomach, caecum and colon and the length of colon were significantly greater in pigs consuming the high-fibre diet than in those on the low-fibre diet. Pigs kept at low temperature had significantly heavier caecums than those kept at the high temperature. Digestibilities of protein, DM and energy were lowest for the high-fibre diet. Only minor amounts of NSP and its constituent sugars were degraded anterior to the ileum, whereas in the hind-gut the fermentation of the total NSP fraction was high, being 0.77 for the high-fibre diet and 0.59 for the low-fibre diet. Feeding the high-fibre diet increased the flow of digesta through the terminal ileum 5-6-fold and an extra 460 g organic matter was fermented daily in the hind-gut compared with pigs fed on the low-fibre diet. The amount of retained energy as a proportion of metabolizable energy decreased in relation to the amount of energy fermented in the hind-gut. Based on the present data it was estimated that the relative value of energy derived from hind-gut fermentation was 0.73 in comparison with energy enzymically digested in the small intestine. There was negligible effect of the temperature--fibre interaction on energy metabolism. However, it could be calculated that the decrease in temperature from 23 degrees to 13 degrees was associated with an increase in heat production by 2.9 MJ/pig per d.

The influence of dietary fibre source and level on the development of the gastrointestinal tract, digestibility and energy metabolism in broiler chickens.

The present study was undertaken to provide detailed information about the effect of fibre source (pea fibre, wheat bran or oat bran) at inclusion levels of 0, 187 and 375 g/kg diet on the development of the digestive tract, nutrient digestibility and energy and protein metabolism in broiler chickens. Heat production was measured using open-air-circuit respiration chambers. Diets with increasing levels of pea fibre decreased the DM in droppings and increased excreta output (2.5-fold) relative to DM intake. Adaptation to increased dietary fibre levels included increases in the size of the digestive system, with pea fibre exerting a stronger impact than wheat bran or oat bran. The length of the intestine, and particularly the length and weight of the caecum, increased with the fibre level. The digestibility of all nutrients also decreased with increasing fibre level. The decrease in the digestibility in relation to NSP for the three fibre sources was bigger for oat bran (0.0020 per g dietary NSP) than for pea fibre and wheat bran (0.0014 and 0.0016 per g dietary NSP) indicating that the cell walls in oat bran (aleurone and subaleurone) had a significant negative effect on the digestibility of cellular nutrients, i.e. protein and fat. The degradation of the NSP constituents was far lower in chickens than found in other animal species such as pigs and rats, thus supporting the view that chickens do not ferment fibre polymers to a great extent. Excretion of organic acids (mainly lactic acid and acetic acid) accounted for up to 2% of metabolizable energy (ME) intake with the highest excretion for the high-fibre diets. H2 excretion was related to the amount of NSP degraded and indicated higher microbial fermentation with increasing fibre levels. The chickens' feed intake responded to a great extent to dietary ME concentration but expressed in terms of metabolic body size (W0.75) ME intake was depressed at the high fibre levels. Dietary NSP was able to explain between 86% (oat bran) and 96% (pea fibre) of the variation in ME concentration. The amount of energy available from fermentation of NSP appears to reach a maximum of 42 kJ/d independent of fibre source and level. Expressed in relation to ME intake the NSP fermentation contributed 3-4%. With increasing fibre intake the partitioning of retained energy between body protein and body fat changed in favour of protein.

Effects of the type and level of dietary fibre supplements on nitrogen retention and excretion patterns.

The hypothesis was tested that fermentable dietary fibre (DF) sources elevate faecal N excretion at the expense of urinary N without affecting N retention. DF that substantially increase fermentation (pectin, sugarbeet and soya bran) or are poorly fermented (crystalline cellulose and maize bran) were fed as supplements to a basal DF-free diet at three dose levels: 0, 50 and 100 g supplement/kg basal diet. The diets were fed to juvenile male Wistar rats for 2 weeks before a 7 d period when faeces and urine were collected. Faecal excretion of N was significantly increased, dose-dependently, by all DF supplements and was positively correlated to faecal bulking. Urinary excretion of N was lower at the high doses of the DF supplements but reached significance only with the highly fermentable (0.68) sugarbeet-supplemented diets. Regression analysis showed that the major part (0.75) of the increase in faecal N excretion due to DF supplementation was balanced by a reduction in urinary excretion; N retention was therefore, at the dose levels used, only affected to a small extent. Only in the maize-bran-supplemented diets were the reductions in N retention significant. The shift in N excretion from urine to faeces can be explained largely by the degree of microbial fermentation in the large intestine caused by the addition of DF supplements and emphasizes the modifying role that certain DF supplements may have on the enterohepatic cycle of N. Possible implications of these findings for patients with liver or renal failure or for conditions when the intake of dietary protein is marginal are discussed.

Fertilizer effects on yield, mineral and amino acid composition, dietary fibre content and nutritive value of leeks.

In pot experiments with greatly differing rates of N, P, S, K and Ca, dry matter (DM) yields of leek stems varied from 25 to 164 g/pot. Total-N and NO3-N concentrations varied from 1.18 to 3.56% and from 10 to 1515 ppm in DM, respectively. Both N applications and P and K deficiency greatly increased total-N and NO3-N content. S applications increased total-S content from 0.047 to 0.359% in DM, of which between approximately 100 to 25% were found in methionine+cystine. Total-N/total-S ratios decreased from 57 to 6 with the highest S level. P and K applications increased their respective content in DM two- and threefold. Severe Ca deficiency reduced Ca content from 0.495 to 0.045%. Iron, zinc, manganese and copper contents varied from 33-69, 14-26, 11-34 and 3.1-5.7 ppm in DM, respectively. Increasing N contents, whether due to N applications or P or K deficiency, decreased the content of all essential and some other amino acids in crude protein. Both S and severe P deficiency had a pronounced negative effect on amino acid composition and chemical score. Only glutamic acid (glutamine) and arginine were increased by increasing N contents. However, expressed as g/kg DM the concentrations of all amino acids were positively correlated with protein content. S and P deficiency reduced total dietary fibre (TDF) content of DM from 28.3 to 18.6% and 17.4%, respectively, of which between 53 and 60% were insoluble dietary fibre (IDF). Digestible energy (DE) was positively correlated with protein content (r = 0.90**). In N-balance trials with rats, increasing protein concentrations (50% of total protein given as casein and supplemented with 1% methionine) raised the true digestibility (TD) of the protein from 44 to 72%. The biological value (BV) of protein was generally high, with a mean of 91.7. N deficiency tended to increase and S deficiency tended to decrease the BV.

Digestibilities of energy, protein, fat and nonstarch polysaccharides in a low fiber diet and diets containing coarse or fine whole meal rye are comparable in rats and humans.

The apparent digestibility of energy, protein, fat and nonstarch polysaccharides (NSP) of a low fiber diet and two high fiber diets containing coarse or fine whole meal rye bread was studied in experiments with humans and rats. Human subjects consumed the experimental diets for 3 wk each in a 3 x 3 cross over design. For the rat diets, duplicate portions of the foods consumed by the human subjects were mixed together, freeze dried and ground. There was a good agreement in the digestibility of energy (humans: 94.7 +/- 0.9, 91.2 +/- 1.2 and 91.6 +/- 1.4%; rats: 95.0 +/- 0.8, 92.5 +/- 1.4 and 91.7 +/- 1.8%) and fat (humans: 95.2 +/- 1.5, 94.4 +/- 1.0 and 94.8 +/- 2.5%, rats: 95.4 +/- 0.9, 94.0 +/- 0.4 and 94.0 +/- 0.4%) for the low fiber diet and the diets containing coarse or fine whole meal bread, respectively. Apparent and true digestibility of protein was consistently lower (P < 0.0001) in humans (apparent digestibility: 90.6 +/- 1.5, 86.2 +/- 1.4 and 86.3 +/- 2.3%; true digestibility: 95.1 +/- 1.5, 90.7 +/- 1.4 and 90.8 +/- 2.2%) than in rats (apparent digestibility: 92.3 +/- 1.1, 89.4 +/- 0.9 and 88.9 +/- 1.0%; true digestibility: 98.3 +/- 1.1, 94.9 +/- 0.9 and 94.2 +/- 1.0%) for all three diets. The digestibility of NSP tended to be lower (P < 0.066) in rats than in humans for the diet containing fine whole meal bread (rats: 59.6 +/- 8.0%, humans: 68.0 +/- 5.2%) and the low fiber diet (rats: 72.1 +/- 10.8%; humans: 80.5 +/- 7.1%), whereas it was similar in both species for the diet containing the coarse whole meal bread (rats: 66.1 +/- 6.0%; humans: 65.8 +/- 9.3%). In spite of some differences in digestibility values, our results suggest that the rat is a suitable model for humans to predict digestibility of nutrients in mixed diets containing cereal fiber sources.

The influence of the period of adaptation on the digestibility of diets containing different types of indigestible polysaccharides in rats.

In balanced experiments with rats the influence of the period of adaptation on nutrient digestibility in diets containing cellulose (CEL), guar gum (GG), pectin (PEC) or retrograded high amylose maize starch (RS) was studied. Inclusion level was 80 g/kg diet DM except for the retrograded high-amylose maize starch, where the level was 316 g/kg diet DM. A diet containing normal maize starch only acted as a control diet (FF). The apparent digestibilities of DM, NSP, starch and protein were determined after adaptation periods of 4 d and 2, 4, 6 and 8 weeks. The digestibility of nutrients was affected by diet (P < 0.001) as well as by the period of adaptation (P < 0.001). The digestibilities of DM, NSP and starch increased asymptotically during the course of the experiment. The asymptotic progress over time was most pronounced for the GG, PEC and RS diets. The estimated periods of adaptation required for stable DM digestibility were approximately 1 week for the GG, PEC and RS diets and < 4 d for the FF and CEL diets. The digestibility of NSP in the GG and PEC diets was also stable after approximately 1 week, while it was stable from < 4 d for the CEL diet. However, PEC increased the faecal content of uronic acids for at least 2 weeks. A stable starch digestibility required 1 month in the case of RS and 3-10 d for the other diets. The high faecal content of glucose for the RS diet decreased during all 8 weeks but was still high at the close of the experiment. The apparent protein digestibility changed over time in a parabolic rather than an asymptotic fashion. The GG, PEC and RS diets increased the amount of N excreted by the faecal route.

Protein quality and digestibility of new high-lysine barley varieties in growing rats.

Four new high-lysine barley mutants, the variety 'Lysimax', with the high-lysine gene lys3a and the mutants mother variety 'Sultan' were grown in a field trial in 1993 at Risø, Denmark. Mutants 609, 1242, 1385 and 1405 yielded in the range of 89 to 98 percent and cv 'Lysimax' yielded 102 percent of cv 'Sultan' (100 percent). One-thousand kernel weights for the mutants were in the range of 87 to 97 percent and cv 'Lysimax' 83 percent of cv 'Sultan' (100 percent). Protein contents of the mutants were slightly higher, in the range of 13.2 to 13.6 percent, than of cv 'Sultan' (13.1 percent) and 'Lysimax' which had a protein content of 12.6 percent. Fat content was higher in 'Lysimax' and in the mutants except for mutant 1385 than in cv 'Sultan' while dietary fibre contents of the barleys were similar. The levels of beta-glucans and starch were usually lower in 'Lysimax' and in the mutants. The highest lysine levels: 4.6, 4.0 and 3.7 g/16 g N occurred in cv 'Lysimax' and mutants 609 and 1405 compared to 3.3, 3.3 and 3.2 for cv 'Sultan' and mutants 1242 and 1385, respectively. Mutants 609 and 1405 and cv 'Lysimax' also had higher levels of threonine, histidine and valine. The increased lysine contents resulted in large, at most 20 percent, increases in biological value; 88.8, 81.7 and 78.3 percent for cv 'Lysimax' and mutants 609 and 1405 compared to 74.2 percent for cv 'Sultan'. True protein digestibilities and energy digestibilities were slightly lower in 'Lysimax' than in 'Sultan', 5.3 and 4.3 percentage units, respectively. It is concluded that the development of high-lysine barley varieties is very beneficial for meeting the requirements of indispensable amino acids for humans and monogastric animals. In addition, nitrogen excretion into the environment is drastically reduced due to the higher biological values of the mutants.

Determination of digestible energy values and fermentabilities of dietary fibre supplements: a European interlaboratory study in vivo.

The performance of methods to determine energy conversion factors for dietary fibre (DF) supplements and fermentability (D) values of their non-starch polysaccharides (NSP) was investigated. Heats of combustion, digestible energy (DE) and D values were determined on five DF supplements in five European laboratories on five separate occasions. In each instance the DF supplements were fed to juvenile male Wistar rats at two doses, 50 and 100 g/kg basal diet, for 3 weeks with food and faeces collected in the 3rd week. Among-laboratory variations in heats of combustion (delta Hc) were < 2%. DE values (kJ/g dry weight) at the upper and lower doses respectively were: 10.4 and 9.9 for a high-methoxyl apple pectin, 9.5 and 9.4 for a sugar-beet DF supplement, 12.2 and 12.7 for soyabean DF supplement, 3.8 and 4.0 for maize bran, and 0.3 and 0.3 for Solka-floc cellulose. Variations among laboratories, among occasions and among animals were < 1, < 2 and < 2.5 kJ/g respectively. The among-occasion: among-laboratory variance ratio for DE was 0.5, suggesting the method performed equally well in all laboratories. There was no evidence of learning of fatigue or fatigue in the performance of the method. D values were also independent of dose and at the high and lower doses were: pectin 0.92 and 0.95, sugar-beet NSP 0.68 and 0.68, soyabean NSP 0.86 and 0.88, maize bran 0.17 and 0.18, cellulose 0.07 and 0.06. Among-laboratory variance tended to increase with decreasing fermentability and ranged from 0.03 to 0.18. The DE and D data were not significantly different from a previously proposed relationship DE = 0.7 x delta Hc x D, where delta Hc is the heat of combustion of the supplement. We conclude that while the among-laboratory variation in the D of difficult-to-ferment NSP is too large for the reliable prediction of energy value the method for the direction determination of DE is both reproducible and repeatable, that DE is independent of dosage of DF supplement up to 100 g/kg diet, and that it is safe to discriminate between energy values with a precision of 3 kJ/g. The conversion of both DE and D to net metabolizable energy for the purpose of food labelling, tables and databases is described.

Gastrointestinal growth in rats as influenced by indigestible polysaccharides and adaptation period.

Hypertrophy of the small intestinal tissue evolved during the initial 9 days in rats fed pectin or guar gum. Hypertrophy of the caecal and colonic tissue continued beyond day 9. Caecal hypertrophy was observed in rats fed pectin, guar gum or resistant starch, while colonic hypertrophy was observed only in rats fed pectin or resistant starch. There is a time lag in the adaptive response of the caecum and colon as compared with the small intestine, at least for dietary polysaccharides. This time lag is suggested to be related to the time required for the microflora to adapt to the dietary PS.

Comparative nutritive value of winged bean (Psophocarpus tetragonolobus (L) DC) and other legumes grown in Tanzania.

Chemical analyses and feeding experiments using rats were conducted to evaluate the nutritive value of winged bean and other legumes (soyabean, green gram, bambarra nuts, pigeon peas, field beans, cow peas) sources grown in Tanzania. Proximate analyses showed that the composition of winged bean was similar to soyabean, while the composition of the other legumes differed considerably. This was also the case for antinutritional constituents and minerals. As to the amino acid composition, the lysine level was high with the highest value in winged bean (7.5 g/16 g N). However, the concentration of methionine and cystine was low which limits their protein quality. Another important amino acid, threonine, was generally high, especially in winged bean (4.3 g/16 g N). With exception of field bean, true protein digestibility was above 80%, soyabean having the highest value (90.7%). The biological value was also highest in soyabean (76.1%) followed by winged bean (69.9%). Utilizable protein was high in soyabean (28.8%) and somewhat lower in winged bean (23.4%). Energy digestibility was around 80%, soyabean having the highest value of 85.8%. The study findings support the idea that winged bean is a good alternative plant protein source in Tanzania.

The influence of dietary fibre on body composition, visceral organ weight, digestibility and energy balance in rats housed in different thermal environments.

The present study was undertaken to provide detailed information on the effect of dietary fibre (DF) level on body composition, visceral organ weight, nutrient digestibility and on energy and protein metabolism of rats housed in cold (16 degrees), warm (24 degrees) or hot (32 degrees) thermal environments. High- or low-fibre diets (257 v. 56 g DF/kg dry matter (DM)) were studied in a 6-week balance experiment (initial body weight about 100 g). Heat production was measured using open-air circuit respiration chambers. Pea fibre and pectin were used to adjust the DF level in the high-fibre diet. The ranking order of daily gain of rats kept in different environments was: 24 degrees > 16 degrees > 32 degrees, while the ranking order for carcass protein was: 16 degrees > 24 degrees > 32 degrees. Rats on the high-DF diet had a lower daily gain than those on the low DF diet, and more protein in DM of empty body weight (EBW) and less fat. The relative weights (g/kg EBW) of liver, heart and kidney decreased when increasing the environmental temperature. The relative weight of the heart was highest in rats on the high DF level, while liver and kidney weights were unaffected by DF. Per kg EBW, the stomach, small intestine, caecum and colon and the length of colon were significantly greater in rats consuming the high-fibre diet compared with those on the low-fibre diet. Rats kept at low temperature had a significantly heavier gastrointestinal (GI) tract than those kept at the highest temperature. Digestibility of protein, DM and energy was lowest for rats fed on the high-fibre diet. Heat production (HP) of fed rats as well as fasting HP decreased significantly as environmental temperature increased. HP as a proportion of metabolizable energy (ME) was significantly lower for rats at 24 degrees compared with the other environmental temperatures. The proportion of energy retained as protein was slightly higher in rats fed on the high-fibre than on the low-fibre diet. Based on the results of the present study the authors measured a net energy value of 5.4 kJ/g DF fermented; approximately 50% of the DF came from peas. Possible implications of the present findings are discussed.

The influence of dietary fibre on protein digestion and utilization in monogastrics.

Current knowledge of the effects of dietary fibre and associated components on protein digestibility and utilization are discussed. Based on the literature it could be shown that the implications and mechanisms behind the effect of soluble and insoluble dietary fibre on protein digestibility and utilization are quite different. Insoluble dietary fibre will increase faecal bulk and faecal nitrogen excretion is primarily due to and increased excretion of cell wall bound protein. Contrary to this, soluble dietary fibre increase faecal bulk and faecal nitrogen due to an increased excretion of microbial nitrogen. A matter of controversy is the influence of dietary fibre on endogenous nitrogen excretion and factors affecting the losses of nitrogen in this way. It is not known if fibre acts as a secretogogue.

Influence of growth conditions on the value of crisphead lettuce. 3. Protein quality and energy density as determined in balance experiments with rats.

Crisphead lettuce was cultivated under different growth conditions. Sixteen batches differed in time of planting (early and late), total nitrogen supply (200 kg N/ha, 150 kg N/ha, 100 kg N/ha, 50 kg N/ha) and time of harvest (early and late). Based on chemical analysis and balance studies on rats the nutritive value of each 16 batches was determined. The protein content increased progressively from 16.00 to 19.88% with fertilization level. This increase in protein caused a significant drop in essential amino acids (g/16 g N) demonstrating a lower biological value of this protein. Early planting or early harvest resulted in a higher protein content than in lettuce of late planting or late harvest. Total dietary fibre content was approximately 25% of DM-and this value was not much influenced by the different growth conditions. Soluble dietary fibre was approximately 20-25% of total dietary fibre. Due to the high fibre content, energy digestibility was relatively low. The contents of Cd and Pb were below what is considered as 'acceptable' levels.