Mineral excretion of rats fed on diets containing faba beans (Vicia faba L.) or faba bean fractions.

The effects on faecal mineral excretion of two commercial varieties (local cultivar and Troy cultivar) of raw faba beans (Vicia faba L., minor) meal (VFM) and its fractions have been studied in growing rats. Diets contained local-VFM (dark seed coat) and Troy-VFM (light seed coat) at 474-500 g/kg diet, hull (VFH) from both varieties at 65 g/kg diet, and the insoluble cotyledon residue (VFCR) obtained from the Troy variety at 237 g/kg diet. Rats were pair-fed on diets which had been supplemented with amino acids to target requirements and contained similar amounts of zinc, manganese, iron and copper. With VFM diets the apparent absorption of Zn and Mn was significantly reduced. On the other hand, with hulls the apparent absorption of Fe was reduced while that of Cu slightly increased. As the amounts of calcium, phosphorus and magnesium in VFM and VFH diets were higher than in the controls, the increased intake resulted in a significant increase in both the apparent absorption and the faecal excretion of these minerals. The inclusion of VFCR in the diet had no significant effect on the mineral content of faeces. The relatively low concentrations of phytate in the bean seeds of 7.8 and 6.7 g/kg for the local and Troy cultivars respectively, could not adequately account for the increased mineral excretion. The results suggest that other seed constituents, possibly the soluble non-starch polysaccharides, may be involved in the elevated loss of Zn and Mn in rats fed on diets containing faba bean for extended periods, while some insoluble structural hull components may interfere with the absorption of Fe from the gut.     

Nutritional response of rats to faba beans (Vicia faba L. minor black 'Kalimattar') and its fractions

The investigations on protein quality of raw faba bean seed meal (Vicia faba L. minor) and its fractions were carried out using rats in two experiments. Two varieties of faba seeds were used, locally grown faba bean 'Kalimattar' or 'black' (KSM) (492 g/kg diet) and its exotic counterpart Vicia faba L. minor 'White' (VFW) obtained from International Centre for Agricultural Research in the Dry Areas (ICARDA) (540 g/kg diet). The pulverized cotyledons of 'Kalimattar' (KMC; 438 g/kg diet), hull (KMH; 78 g/kg diet) as well as cotyledons of 'White' faba bean (VFWC; 470 g/kg diet) and hull (VFWH; 82 g/kg diet) fractions were tested. All diets were made isocaloric and isonitrogenous, however, without addition of individual amino acids to the target requirements. Performance of rats fed on both locally grown KSM and exotic FBW meal-fed rats were found to be inferior to those obtained from the rats fed on standard protein diet. The net protein utilization (NPU) of the rats fed on this seed meal was comparatively better than those obtained from the VFW. Replacement of standard protein with cotyledons from the either of the seed (KMC and VFWC) depressed food intake and protein utilization. This was due, in part, to the excretion of comparatively higher amount of nitrogen in faeces. Inclusion of KMH in the diet had no adverse effects on any variable studies as compared to the VFWH, which was found to impose severe restriction on the absorption of standard protein added to this diet. As a result, body weight gain, and NPU value were significantly lower than those obtained from the KMH. We conclude that the locally grown faba bean 'Kalimattar' is better than those of exotic 'White' cultivar and may contain less antinutritional substances. However, this warrants further investigations.     

The utilization of raw and autoclaved faba beans (Vicia faba L., var. minor) and faba bean fractions in diets for growing boiler chickens

The effects of the inclusion of raw and autoclaved whole faba beans (Vicia faba; RFB and AFB respectively) or faba bean fractions (cotyledons and hulls) in diets for growing broiler chickens (0-4 weeks of age) on performance, intestinal physiology and jejunal histological structure have been studied in three experiments. Significant decreases in body-weight as well as lower food consumption and higher food intake:weight gain ratio were observed in those animals fed on diets containing 250, 350 and 500 RFB/kg in the diet. Birds fed on AFB diets (500 g/kg) had significantly greater body-weights than chicks fed on RFB or raw faba bean cotyledons (RC). Significant increases in the relative lengths of duodenum, jejunum, ileum and caeca, pancreas relative weight, and intestinal transit time of birds fed on diets containing 250, 350 and 500 g RFB/kg compared with control birds were observed. Including AFB (500 g/kg) in the diet significantly increased body-weight and significantly decreased pancreas weight compared with RFB (500 g/kg)-fed birds. The inclusion of RFB hulls had no effect on these variables. Dehulling or autoclaving of faba beans, or both, proved to have no significant effect on relative lengths of duodenum, jejunum, ileum and caeca, nor on caecal volatile fatty acid concentration in birds fed on 500 g faba beans/kg diet. Electron microscopy of the jejunal mucosa revealed discrete hyperplasia of polysomes and mitochondrial swelling in those animals fed on AFB (500 g/kg) or AC (426.4 g/kg). Pronounced strangulations were also observed along the microvilli, whose length was similar to that of control birds. The inclusion of RFB hulls, either autoclaved or raw, led to no ultrastructural changes in the enterocytes, as detected by electron microscopy. Birds fed on diets containing the cotyledons of RFB (RC, 426.4 g/kg) rather than whole RFB showed the same ultrastructural disorders as RFB (500 g/kg)-fed birds. The present study shows that factors other than those usually claimed, i.e. protease inhibitors, phytates, tannins and lectins, may be contributing to the low nutritional value of V. faba seeds for growing chickens.     

The effect of varying crude protein level and the proportions of fibre in diets containing a mixture of meat-and-bone meal and wheat bran as the only protein source on nitrogen balance indices and energy digestibility in the rat

1. The experiment was designed to investigate the effect of protein level in diets on apparent protein digestibility (AD), true protein digestibility (TD), biological value (BV), net protein utilization (NPU) and energy digestibility (DE) in rats. The design involved fourteen dietary treatments in which a combination of wheat bran and meat-and-bone meal (1:1, w/w dry matter (DM) basis) was the only nitrogen source. Crude protein (N x 6.25; CP) level ranged from 60 to 329 g/kg DM in approximately even increments. All diets contained a constant level of minerals and vitamins. The balance of the diet consisted of a N-free mixture. 2. AD increased from 0.602 at 60 g CP/kg DM to 0.702 at 120 g CP/kg DM, with little change at the higher levels of dietary protein. The fitting of a curve indicated an asymptote of 0.721. 3. TD did not vary significantly between 60 and 225 g CP/kg DM (mean 0.781). At the higher protein levels there was a slight but significant reduction in the mean value (0.758). 4. BV increased from 0.475 at 60 g CP/kg DM to 0.498 at 80 g CP/kg DM where it plateaued, and then from 160 g CP/kg DM it decreased at an increasing rate to 0.216 at 329 g CP/kg DM. 5. The response in NPU closely reflected that obtained with BV, rising from 0.370 to 0.384, then declining to 0.162 at the highest CP concentration. 6. DE decreased linearly from 0.851 at 60 g CP/kg DM to 0.617 at 329 g CP/kg DM. 7. The results confirmed that AD values should only be compared at a defined protein level. TD was essentially independent of dietary CP level, except for a small reduction above 250 g CP/kg, whereas BV and NPU were stable only within the range 80-140 g CP/kg DM. DE was negatively related to dietary CP and fibre level.     

Carbohydrates digestibility and faecal nitrogen excretion in rats fed raw or germinated faba bean (Vicia faba)- and chickpea (Cicer arietinum)-based diets

Raw or germinated faba bean (Vicia faba minor var. Alameda) and chickpea (Cicer arietinum kabuli var. Athenas) seed meals were incorporated in essential amino acid-supplemented and energy-equalized diets for growing (65 (SD 1) g) male Wistar rats as the only sources of dietary protein. A lactalbumin-based diet was used as the control. Faecal dry weight and N excretion of animals fed legume-containing diets were greater (P<0.01) and DM digestibility lower (P<0.01) than controls. Apparent faecal digestibilities of amino acids were found to be not different or lower (P<0.01) than controls in rats fed diets containing legume seeds, either germinated or not. Total diaminopimelic acid (DAPA) and purine bases excretion were significantly (P<0.01) higher than controls in rats fed both legume seed meals. Faecal bacterial N calculated according to DAPA or purine bases values was similar and significantly higher (P<0.01) than controls in rats fed legume seed meals. Bacterial N accounted for 50 to 80 % of total faecal N in rats fed legume diets. Apparent faecal N digestibility values (53-65 %) of rats fed legume-based diets were lower (P<0.01) than controls, but became substantially higher (85-92 %) when calculated taking into account bacterial N values. Faecal NSP digestibility values for legume diets were 40-57 g/100 g ingested. Germination decreased starch faecal excretion (P<0.05) and increased (P<0.05) faecal starch and NSP digestibilities of faba bean seeds.     

Nutritional effects of field bean (Vicia faba L.) proteinase inhibitors fed to rats.

1. Weanling rats were fed on purified-casein diets containing active and inactive (autoclaved) field bean (Vicia faba L.) proteinase inhibitors (PI) at levels of 1.25, 2.5, 5.0 and 10 g/kg. Diets containing raw- and autoclaved-field-bean meal (FBM) were also given. The body-weight gain, protein efficiency ratio (PER); i.e. the ratio of the live weight gain in g/g of protein consumed and apparent nitrogen digestibility were determined 7, 14 and 21 d after the start of the trial. 2. Significant growth depression (P less than 0.001) was observed in rats given diets containing 2.5 g/kg PI (27--35%). In rats fed on raw FBM growth depression was severe after 7 d (57%). 3. Food intake was depressed at PI inclusion levels of 5 g/kg and higher between 14 and 21 d. 4. PER was depressed significanlty (33-44%) in rats given diets containing the active PI at all levels after 7 d. The protein utilization of all casein diets was higher than that of the FBM diets. 5. Apparent N digestibility was depressed in rats fed on diets containing 10 g/kg PI by 9 and 7% at 14 and 21 d respectively. The N digestibility of both raw and heated FBM was similar at approximately 84%. 6. It was concluded that the PI are not the main factors responsible for the growth depression observed when raw FBM is fed to rats.     

Expression of the insecticidal bean alpha-amylase inhibitor transgene has minimal detrimental effect on the nutritional value of peas fed to rats at 30% of the diet.

The effect of expression of bean alpha-amylase inhibitor (alpha-AI) transgene on the nutritional value of peas has been evaluated by pair-feeding rats diets containing transgenic or parent peas at 300 and 650 g/kg, respectively, and at 150 g protein/kg diet, supplemented with essential amino acids to target requirements. The results were also compared with the effects of diets containing lactalbumin with or without 0.9 or 2.0 mg bean alpha-AI, levels equivalent to those in transgenic pea diets. When 300 and 650 g peas/kg diet were fed, the daily intake of alpha-AI was 11.5 or 26.3 mg alpha-AI, respectively. At the 300 g/kg level, the nutritional value of the transgenic and parent line peas was not significantly different. The weight gain and tissue weights of rats fed either of the two pea diets were not significantly different from each other or from those of rats given the lactalbumin diet even when this was supplemented with 0.9 g alpha-AI/kg. The digestibilities of protein and dry matter of the pea diets were slightly but significantly lower than those of the lactalbumin diet, probably due to the presence of naturally occurring antinutrients in peas. The nutritional value of diets containing peas at the higher (650 g) inclusion level was less than that of the lactalbumin diet. However, the differences between transgenic and parent pea lines were small, possibly because neither the purified recombinant alpha-AI nor that in transgenic peas inhibited starch digestion in the rat small intestine in vivo to the same extent as did bean alpha-AI. This was the case even though both forms of alpha-AI equally inhibited alpha-amylase in vitro. Thus, this short-term study indicated that transgenic peas expressing bean alpha-AI gene could be used in rat diets at 300 g/kg level without major harmful effects on their growth, metabolism and health, raising the possibility that transgenic peas may also be used at this level in the diet of farm animals.     

The digestion of perennial ryegrass (Lolium perenne cv. Melle) and white clover (Trifolium repens cv. Blanca) by grazing cattle

1. Pure swards of perennial ryegrass (Lolium perenne cv. Melle) as a primary growth (May), trimmed primary growth (early June) and regrowth (late June), and white clover (Trifolium repens cv. Blanca) as a mature primary growth (July) and vegetative regrowth (August), were grazed by twelve Friesian steers (mean body-weights throughout experiment 152-231 kg) at daily allocation rates of forage which provided dry matter (DM) intakes ranging from 28 to 36 g/kg body-weight). 2. Total nitrogen contents of the three ryegrasses declined with season (37-20 g/kg DM), but in vitro organic matter (OM) digestibilities were relatively constant (0.76-0.79). The clovers had higher N (average 36.6 g/kg DM) and lower fibre and water-soluble carbohydrate contents than the grasses, and in vitro OM digestibilities of 0.70 and 0.76 respectively. 3. Duodenal digesta samples were obtained, using a portable sampling apparatus from the animals grazing the pasture, and estimates of the flow of nutrients into the small intestine were derived using two indigestible markers which were continuously infused into the rumen using a portable infusion apparatus. Forage intakes were calculated from estimates of faecal output of indigestible OM and the predicted in vivo OM digestibilities of the forages consumed. Coefficients of variation for OM flow to the small intestine and OM intake were 11.8 and 10.9% respectively. 4. The apparent digestion of OM in the rumen ranged from 722 to 741 g/kg digestible OM intake and from 681 to 711 g/kg digestible OM intake for the grass and clover diets respectively. Substantial losses of ingested N before the small intestine were measured on all diets except the regrowth ryegrass. Losses were 0.30 and 0.40 g/g N intake on the primary growth ryegrass and the regrowth clover respectively; N contents were 37 and 39 g/kg DM respectively. 5. Comparison of the values obtained at pasture with that obtained when similar diets were offered to housed cattle (Beever et al. 1985) indicated that combined relations relating duodenal OM and non-ammonia-N (NAN) flows to OM and N intakes respectively could be established for each diet. For two diets (primary-growth grass and regrowth clover) the relations were curvilinear; for the remaining diets, the derived relations were linear.(ABSTRACT TRUNCATED AT 400 WORDS)     

Modifications in plasma cholesterol and apolipoproteins of hypercholesterolaemic rats induced by ethanol-soluble factors of Vicia faba

High-fat-high-cholesterol diets containing casein or a Vicia faba bean (faba bean) protein concentrate as the protein source were given to rats for 5 weeks. When the faba bean protein concentrate or its ethanol extract was present in the diet, a marked decrease was found in the level of circulating cholesterol associated with the lower-density lipoproteins (very-low-, intermediate- and low-density lipoproteins) compared with the level found on the diets containing casein or the faba bean protein concentrate deprived of ethanol-soluble factors. Alterations in apoprotein pattern were detected after the different dietary treatments. In particular, apoA-I appeared in an unusual form with electrophoretic mobility faster than normal in all lipoprotein fractions after feeding the diets that did not lower plasma cholesterol. When the diets contained the faba bean protein concentrate or its ethanol extract, the apoA-I disappeared from the lower-density lipoproteins but its normal form and the unusual one were apparent in the high-density lipoproteins. A moderate increase in faecal excretion of acidic steroids was found after feeding the diets containing the ethanol-soluble factors, irrespective of the protein source. The results are discussed in relation to the presence of saponin and polyunsaturated lecithin in the ethanol extract of the faba bean protein concentrate.     

Effects of the whole seed and a protein isolate of faba bean (Vicia faba) on the cholesterol metabolism of hypercholesterolaemic rats

The aim of the present work was to analyse the hypocholesterolaemic efficiency of a Vicia faba-protein isolate in relation to the intact legume. In addition, the mechanisms underlying the effects of this isolate were investigated. Hypercholesterolaemic rats were divided into three groups and fed high-fat diets rich in cholesterol-containing casein, whole seeds of Vicia faba or the protein isolate of faba beans as protein source, for 2 weeks ad libitum. The protein isolate was prepared by isoelectric precipitation and spray dried. Analyses of serum, liver and faeces, as well as of the activity of hepatic 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase, were assessed by enzymatic methods. The rats fed on Vicia faba diets showed significantly lower body weights and energy intakes than rats fed on casein diets. The whole-seed diet induced a significant reduction in plasma triacylglycerol. Feeding rats on diets containing faba bean seeds, or the protein isolate, induced a significant decrease in plasma (LDL+VLDL)-cholesterol but not in HDL-cholesterol. Hepatic cholesterol and triacylglycerol were also reduced. The hypocholesterolaemic effects of Vicia faba were not the result of a reduction in cholesterol synthesis as assessed from HMG-CoA reductase activity, but the result of an increase in steroid faecal excretion. The faba bean-protein isolate obtained under our experimental conditions was useful in improving the metabolic alterations induced by feeding with a hypercholesterolaemic diet compared with casein. The effectiveness of the whole seeds was higher than that of the protein isolate.     

The sequential feeding of growing chickens.

1. Male chickens, I week old, were fed alternately for 6 or 12 h periods with diets complementary in their amino acid composition. The isonitrogenous, isoenergetic diets were based on fish meal or sunflower meal as the sole source of protein, or fish meal-sunflower (40:60, w/w); each diet contained 120 g crude protein/kg. Other groups of chickens were given these diets ad lib. 2. Net protein utilization (NPU) values obtained after a I-week experimental period indicated that sequential feeding for bot 6 and 12 h resulted in significantly improved responses compared with chickens given the same diets ad lib. These results suggested that the two protein sources, although provided at separate times, could complement each other. 3. In certain treatments there was a 6 or 12 h fasting period between feeding periods to reduce the effect of nutrients from the previous period. 4. For alternate feeding and fasting periods of 6 h with the combined diet, food intake and gain in body-weight were both significantly reduced compared with the corresponding values for the combined diet fed ad lib. The NPU value was virtually the same for both treatments. For 12 h periods of alternate feeding and fasting the gain in body-weight was only just significantly lower than that for the control group (combined diet fed ad lib.), but the NPU value was highly significantly better than that for the control group. 5. For the treatments which included 6 and 12 h fasting periods between the two single-protein diets, the food intake and gain in body-weight were significantly lower compared with the treatment groups given alternate feeding thd fasting periods of either 6 or 12 h with the combined diet. The NPU values for the two groups given 12 h alternate feeding and fasting periods differed significantly, whereas the NPU values for the two groups given 6 h feeding and fasting periods were the same.     

Protein quality in cereals and pulses. 3. Bioassays with rats and chickens on sorghum (Sorghum vulgare Pers.), barley and field beans (Vicia faba L.). Influence of polyethylene glycol on digestibility on the protein in high-tannin grain.

1. Two preceding papers in this series describe the application of microbiological and other in vitro tests in the evaluation of sorghum (Sorghum vulgare Pers.), field beans (Vicia faba L.) and barley, and in assessing the influence of polyethylene glycol (PEG 4000) on the nutritional availability of the methionine. The present paper gives for comparison the results of bioassays on some of the same test samples. Net protein utilization (NPU) in rats was measured by the nitrogen balance method, and N digestibility in chickens by the ileal analysis procedure. 2. In rat tests on sorghum, N in grain of high-tannin varieties was poorly digested. Supplementation of the test diets with 0.1 g PEG 4000/g protein gave a large improvemnet, which was partly offset by an apparent decrease in biological value (BV). With chickens N digestibility was even lower, and was similarly improved with PEG 4000. Treatment of high-tannin grain with ammonia solution was also effective in improving N digestibility. 3. With low-tannin sorghum the amino acid digestibilities were uniformly high and were not affected by addition of PEG to the test diet. With high-tannin sorghums they were low and less uniform, and were much improved by PEG 4000. 4. With field beans, the influence of the seed-coat tannin on protein utilization was much less pronounced than with sorghum. In chickens there was a significant effect (P less than 0.05) of PEG 4000 on N idgestibility in a high-tannin variety. With rats the effect was smaller and not significant. 5. In four samples of barley. N digestibility was high (0.87--0.96) and was not further improved by PEG 4000. The BV of a high-lysine cultivar proved marginally inferior to that of a normal variety. Possible reasons for this are discussed. 6. Over all, the results were closely consistent with those from microbiological tests with Streptococcus zymogenes.     

Effect of fiber-rich brown seaweeds on protein bioavailability of casein in growing rats

The effect of three subtropical fiber-rich brown seaweeds, Sargassum hemiphyllum (Turn.) C. Ag., Sargassum henslowianum C. Ag. and Sargassum patens Ag., on protein bioavailability of casein were evaluated by growing rats. The effect of the fiber-rich seaweeds was determined by comparing the net protein ratio (NPR), true protein digestibility (TD), nitrogen balance (NB), biological value (BV), net protein utilization (NPU), and fecal and urinary nitrogen loss of seaweed-based diet groups with those of the cellulose-based control group. There were no significant differences on NPR and urinary N loss in all diet groups. However, the values of TD (range 85.6-89.6%), BV (range 96.9-97.5%), NPU (range 83.5-86.8%) and NB (range 145-150 mg/rat/day) in all seaweed-based diet groups were significantly (p<0.05, one-way ANOVA, Tukey-HSD) lower than those of the control group. On the contrary, the fecal weight (range 5.59-6.30 g/rat/day) and fecal nitrogen (N) loss (range 31.1-41.2 mg/rat/day) of rats fed seaweed-based diets were significantly (p<0.05, one-way ANOVA, Tukey-HSD) higher than that of the control one. However, the differences on the body weight gain and weight of internal organs including liver, kidney and spleen between the seaweed-based diets and control groups were insignificant except that the weight of caecum of rats fed seaweed-based diets was significantly (p<0.05, one-way ANOVA, Tukey-HSD) higher than that of control group. The possible mechanism of fiber-rich brown seaweeds in affecting the protein bioavailability of casein and their related nutritional implications were discussed.     

The digestibility in piglets of faba bean (Vicia faba L.) as affected by breeding towards the absence of condensed tannins.

Seed samples from two near-isogenic faba bean (Vicia faba L.) lines were examined for the levels of so-called anti-nutritional factors (ANF). From the ANF known to be present in faba beans, trypsin inhibitor activity, functional lectins, condensed tannins and pyrimidine glycosides were analysed. It was concluded that the lines differed only in the content of condensed tannins being < 0.5 g/kg and 5.2 (SD 0.2) g/kg for the low (LT)- and high (HT)-tannin lines respectively. In addition, the level of pyrimidine glycosides in the LT line was slightly higher than that in the HT line. The LT line showed a reduced proportion of the seed coat (105 v. 119 g/kg) and a lower seed weight (0.85 v. 1.01 g). The apparent ileal and faecal digestibility values of dry matter and nitrogen from the HT and LT line were determined for piglets which were fed on diets containing chromium oxide as a marker. The mean apparent ileal and faecal digestibility values for dry matter for the LT line were 0.694 and 0.889 and for N 0.828 and 0.879 respectively. For the HT line, these values were approximately 0.05 and 0.10 lower (P > 0.05). A multienzyme technique was used to predict the in vitro protein digestibility (IVPD) of the two lines. The IVPD of the LT line was 0.965 and about 0.05 higher than the HT line, confirming the difference in digestibility as measured in vivo. The present study shows the positive effects on digestibility of removal of condensed tannins in faba beans which was achieved by plant breeding.     

Comparative effects of wheat bran and barley husk on nutrient utilization in rats. 1. Protein and energy

1. The present work with growing rats was undertaken to compare the effect of wheat bran and barley husk on nutrient bioavailability. The experiment involved a total of nine dietary treatments consisting of a control group, without wheat bran or barley husk, and two series of four groups with increasing amounts of fibre from 50 to 117 g/kg dry matter (DM) from the two fibre sources. Dietary nitrogen concentration was kept constant at 15 gN/kg DM by adjusting the diets with an N-free mixture. Protein sources were casein, fortified with methionine and white wheat flour. True protein digestibility (TD), biological value (BV), net protein utilization (NPU) and digestible energy (DE) were estimated. 2. TD decreased when total dietary fibre (TDF) increased, the effect being greater in the case of wheat bran. The difference in response can be explained by the larger N contribution from bran than from barley husk. N from barley husk was actually digested less than N from wheat bran. 3. Changes in TD due to fibre were small, both for wheat and barley husk. It was concluded that decreased TD with fibre at moderate levels was due to poor digestibility of the N associated with the fibre source rather than decreased digestibility of N from other dietary components. 4. BV was only marginally affected by the fibre levels, indicating that the relatively high lysine content in both wheat bran and barley husk had a low availability. 5. Wheat bran and barley husk showed almost the same negative effect on DE and DM digestibility (DMD). DMD correlated significantly with DE, demonstrating that DMD is a simple and convenient means of monitoring DE.     

Nutritional evaluation of protein and starch of mature Canavalia gladiata seeds

Evaluation of true digestibility (TD), biological value (BV) and net protein utilisation (NPU) of diets made with raw and processed seed flour from mature Canavalia gladiata seeds were carried out with male Sprague-Dawley rats. The weight gain of the rats fed with diets containing raw whole seed and raw cotyledon alone were significantly lower (P = 0.05) than that of the group fed with the reference diet. Processing the cotyledons (dry-autoclaved or roasted) significantly (P < or = 0.05) increased the weight gain of the rats when compared to the weight gain of rats fed diets prepared with raw seed flour. NPU of raw (whole seed 13.8; cotyledon 27.6) was significantly lower (P < or = 0.05) than the reference diet (79.5). The NPU of processed samples was also significantly lower (P < or = 0.05) when (dry-autoclaved 25.1; roasted 25.1) compared to the reference diet fed group (79.5). The BV of the processed samples (dry-autoclaved 31.1; roasted 37.7) was significantly lower (P < or = 0.05) than that of raw (53.6) cotyledon. In contrast TD increased (P < or = 0.05) with processing (dry-autoclaved 80.9; roasted 65.9) when compared to raw cotyledon (51.4). In vitro protein digestibility for the raw whole seed and cotyledon was 71.7 and 70.1% respectively. In vitro starch digestibility of raw and processed cotyledon flour samples indicated dry-autoclaved sample to have the highest digestibility.     

Non-essential nitrogen and protein utilization in the growing rat

Three series of nitrogen-balance experiments were carried out on growing rats fed on purified isonitrogenous diets (16 g N/kg) to study the importance of non-essential N and the essential:total N (E:T) ratio for attaining maximum N balance (NB) and biological value (BV) of protein. Minimum dietary levels of asparagine, proline and glutamic acid required for maximum NB and BV were estimated to be 1.0, 2.0 and 5.0 g/kg respectively. In an essential amino acid-based diet, the levels of individual amino acids were successively reduced to 110% of the requirement. Reducing the level of arginine, lysine or methionine + cystine resulted in a significant increase in NB and BV while the response of rats given the isoleucine-reduced diet significantly decreased. Addition of asparagine, proline and glutamic acid in the estimated minimum amounts to an essential amino acid-based diet resulted in a significant increase in NB and BV. A further significant increase was found when the levels of arginine, lysine and methionine + cystine in the diet were reduced to 110% of the requirement. The performance of rats fed on the latter diet was similar to that of rats given a diet with the optimum E:T ratio. It is concluded that the optimum protein utilization may be influenced by the presence of some non-essential amino acids and by the surplus of some essential amino acids rather than by the E:T ratio per se.     

Nutritive efficiencies of lactalbumin and wheat gluten at very low levels of intake in adult rats

The nutritive values of proteins in relation to their intake levels were evaluated by feeding adult male rats weighing 250 g diets containing 0%, 0.39%, 0.78%, 1.56%, 2.34%, 3.90%, 7.79% and 15.58% lactalbumin or wheat gluten for three weeks. The biological values (BV) of both proteins were high at low levels of protein intake but decreased with increase in protein intake. The BV of wheat gluten was estimated to be about 100 at a level of intake of 1.56% but only 25 at a level of 15.58%. Similarly, the BV of lactalbumin decreased with increase in the protein level, being 67 at a level of 7.79%. The BVs of both proteins at low levels of dietary protein (below 2.34% of lactalbumin or 0.78% of wheat gluten) were apparently more than 100 because urinary N excretion was less than endogenous N. The BVs also decreased with time during the three-week test period. It is concluded that BV of a protein is not a fixed value but varies with the experimental conditions especially with changes in the amount of intake, and that differences in the qualities of various proteins cannot be compared quantitatively at a single level of protein. The results were briefly discussed in relation to protein requirements.     

The effect of protein quality and fibre level in the diet and microbial activity in the digestive tract on protein utilization and energy digestibility in rats

Two nitrogen-balance experiments were performed with growing rats to test the effect of dietary fibre level, protein quality and antibiotic inclusion on microbial activity, N excretion patterns and energy digestibility. Each experiments involved eight dietary treatments in a 2 X 2 X 2 factorial design, with five rats per treatment. The eight treatments resulted from a combination of two protein treatments, two fibre treatments and two antibiotic treatments. In Expt 1 the protein was provided as barley, or barley plus 2 g L-lysine hydrochloride/kg dry matter (DM) (at 15 g N/kg DM) and in Expt 2 as soya-bean meal or soya-bean meal plus 2 g DL-methionine/kg DM (at 15 g N/kg DM). In both experiments the basal diet was provided with or without additional fibre as 100 g barley husk/kg DM and with or without antibiotic as 7 g Nebacitin/kg DM. With both barley and soya-bean meal, true protein digestibility (TD) was improved with the addition of amino acids. Only with the soya-bean meal diets was TD increased with Nebacitin treatment, with the effect of Nebacitin and methionine being additive. Barley husk slightly reduced the TD of soya-bean meal. The effect of treatments on biological value (BV) was considerable. Lysine increased BV of the barley diet from 0.741 to 0.815 whereas Nebacitin reduced BV from 0.799 to 0.757. Methionine increased the BV of soya-bean meal from 0.754 to 0.911 while BV was reduced by Nebacitin from 0.843 to 0.821 and by barley husk from 0.845 to 0.820.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of dietary protein concentration and ambient temperature on the energy, protein and water metabolism of the rat

Groups of rats (n 8) were offered, to appetite, diets containing 10 (LP), 25 (MP) and 45 (HP)% of gross energy as protein energy from 45 d of age to slaughter 50 d later. At 53 d of age, half the rats on each diet were left at 22 degrees while the other half were transferred to 6 degrees. Water balances were measured daily, and digestibilities of energy and nitrogen and the metabolizability of the diets were measured for each rat over a 7 d period at some stage between the age of 74 and 95 d. The rats were slaughtered at day 95 and their carcasses were analysed for protein, lipid, energy and ash contents. Energy expenditure was calculated as the difference between metabolizable energy intake and energy retained. Growth performance was best on the MP diet at both temperatures. At 22 degrees the rate of gain of body-weight and of energy retention, although not of protein, were slightly reduced on the HP diet while overall performance was markedly inferior on the LP diet. At 6 degrees the LP diet, while not so good as the MP diet, led to significantly better all-round growth performance than did the HP diet. Cold increased the energy expenditure of the rats by 50% (109-138 kJ/d); the increase was greater for the LP group than for the HP group. Intrascapular brown adipose tissue hypertrophied in response to cold and to the LP diet. Adrenal gland size was significantly increased by cold exposure and by increasing level of dietary protein concentration. Urine volume was more closely related to the intake of protein than to that of energy. Urinary N concentration for the HP rats was approximately double that for those on the LP diet. Cold-exposed rats had a high water content in their fat-free carcasses, but there were no differences between the dietary treatments.