Comparison of methods to determine the endogenous amino acid flow at the terminal ileum of the growing rat

The aim was to compare a recently developed peptide alimentation method and the protein-free and regression methods for determining endogenous ileal nitrogen (N) and amino acid excretion in the rat, and to apply the endogenous loss estimates to determine the true ileal digestibility of a meat and bone meal (MBM). Preliminary investigations determined the effect of the time of sampling of digesta after a meal (slaughter method) for rats given a protein-free or an enzymically hydrolysed casein (EHC) based diet, on ileal digesta and endogenous N excretion. There was a significant (P < 0.05) effect of the time of sampling on the amount of digesta collected and the endogenous N excretion for both the EHC and protein-free fed rats. The amount of digesta collected from the terminal 20 cm of ileum and the endogenous N excretion for both the EHC and protein-free fed rats were greatest and least variable at 3 h post-feeding. In the main study, endogenous ileal amino acid excretions were determined in the growing rat fed an EHC-based diet (n = 6) and with subsequent treatment of the digesta using ultrafiltration or in six rats given a protein-free diet or by extrapolation from data for 30 animals given five diets which contained graded levels of MBM as the sole protein source. For the EHC treatment, the ileal digesta precipitate plus retentate was used to determine the endogenous flows. The ultrafiltration step excludes unabsorbed dietary amino acids from the measure of endogenous loss. Chromic oxide was the reference marker in all diets. The endogenous N flows determined by the protein-free and regression methods were similar but both significantly (P < 0.01) lower than those for rats fed the EHC-based diet. The mean endogenous ileal N flows determined by the peptide alimentation method, the protein-free and regression approaches were 1866, 1103 and 1019 μg g^?1 freeze dry matter intake, respectively. The endogenous amino acid flows at the terminal ileum were lower when determined using the traditional protein-free or regression methods. The true ileal digestibility coefficients for MBM were considerably higher based on the EHC versus protein-free endogenous flows.     

The effect of amino acid and peptide alimentation on the determination of endogenous amino acid flow at the terminal ileum of the rat

Endogenous ileal amino acid (free + bound) flow was determined in four 190-g male rats given a diet whose sole nitrogen source was enzyme hydrolysed casein and compared with that of six rats whose diet contained synthetic amino acids as the only nitrogen source but excluding alanine, glutamic acid and serine, and six rats fed a protein-free diet. The enzyme hydrolysed casein, a mixture of free amino acids and oligopeptides, was assumed to be completely absorbed in the small intestine of the rat. A further seven rats were given an enzyme hydrolysed casein-based diet and their ileal digesta were treated, post-collection, with perchloric acid to precipitate soluble proteins. The latter procedure removed the need to assume complete absorption of the casein nitrogen. The endogenous flow of amino acids for enzyme hydrolysed casein-fed rats was higher than that for the protein-free diet (P < 0.05) which did not differ from the synthetic amino acid diet for the flows of alanine, glutamic acid and serine. The high apparent digestibility of the synthetic amino acids not excluded from the diet indicated that their ileal excretions were mainly of endogenous origin. It would appear, therefore, that the protein deplete state per se does not influence endogenous amino acid flow at the terminal ileum of the growing rat, but there is a direct effect of small peptides on the net loss of endogenous amino acids from the small intestine. The estimates of endogenous amino acid flow obtained following the perchloric acid treatment of digesta were unrealistically low and thus inconclusive, but raised doubt as to the eficiency of perchloric acid in precipitating protein from rat ileal digesta.     

Endogenous amino acid flow at the terminal ileum of the rat determined under conditions of peptide alimentation

The study aimed to determine endogenous ileal amino acid excretion in the growing rat fed an enzymically hydrolysed casein (EHC) based diet with subsequent treatment of the digesta using ultrafiltration technology. Comparison was made with endogenous excretions obtained from rats fed an EHC-based or a protein-free diet and without any treatment of the ileal digesta. Preliminary investigations were made to determine the filtration efficiency of the ultrafiltration devices and to examine three alternative prefiltration treatments, trichloroacetic acid (TCA) and perchloric acid (PCA) precipitation, and centrifugation (SPIN). In the preliminary work, 15 purified protein, peptide and amino acid solutions were ultrafiltered using a molecular weight (MW) exclusion limit of 10000 Da, and the recovery of nitrogen indicated an effective filtration (generally >90% separation) on nominal molecular weight. Further, fresh rat ileal digesta samples were treated with either TCA, PCA or SPIN. The resulting supernates were ultrafiltered and the fractions were analysed for nitrogen and amino acids. The precipitates contained 23, 57 and 41% of the total nitrogenous material for the TCA, PCA and SPIN treatments, respectively, indicating that PCA was the most effective precipitant. In the main study, twelve 100-g male rats were fed either an EHC-based diet or a protein-free diet, and samples of ileal digesta were collected after slaughter. The digesta from the six EHC-fed rats were ultrafiltered after centrifugation, and the high molecular weight fraction was added to the precipitate. Endogenous ileal amino acid flows were determined for the total digesta and for the digesta following the centrifugation plus ultrafiltration treatment. The endogenous amino acid flows were generally higher for the total digesta than for the digesta following centrifugation plus ultrafiltration and significantly so (P<0.05) for lysine, glutamin acid and proline. The protein-free fed rats had significantly P<0·05) lower amino acid flows than those rats fed the EHC-based diedt (ultrafiltration treatment), the greatest differences occurring for isoleucine, serine, glutamic acid, valine, leucine, alanine and threonine.     

Endogenous lysine and other amino acid flows at the terminal ileum of the growing pig (20 kg bodyweight): The effect of protein-free,synthetic amino acid,peptide and protein alimentation

Twenty-four crossbred pigs of 15 kg initial bodyweight were fed four semi-synthetic diets for 10 days according to a completely randomised design. The study aimed to determine the effects of state of body nitrogen balance and the presence of dietary peptides and protein in the digestive tract on the excretion of endogenous amino acids from the ileum of the pig. Endogenous lysine excretion was determined for pigs given a protein-free (PF) diet, an enzymically hydrolysed casein- (EHC), a zein- (ZN) or a synthetic amino acid- (SAA) based diet. Digesta from the EHC-fed animals were centrifuged and ultrafiltered after collection and the precipitate plus retentate fraction was used to determine the endogenous flows. Such processing excludes unabsorbed dietary amino acids from the measure of endogenous loss. ZN is naturally deficient in lysine and tryptophan and these two amino acids were omitted from the synthetic amino acid-based diet to allow direct measurement of endogenous lysine flow. Pigs given the ZN and SAA diets received free lysine and tryptophan orally throughout the study except for the final 2 days of the study, when these amino acids were infused intravenously. Endogenous flows for amino acids other than lysine were determined for pigs given the PF and EHC diets. On the final day of the study the pigs were given their daily dietary allowance hourly and killed 10 h after the start of feeding. Digesta were collected from the terminal ileum (20 cm anterior to the ileo-caecal junction) and endogenous flows were determined by reference to the marker chromic oxide. The mean endogenous ileal lysine flows for the ZN- and EHC-fed pigs were not significantly different (overall mean, 419 mg kg^?1 dry matter intake), but were higher (P < 0.05) than those for the PF- and SAA-fed pigs (overall mean, 268 mg kg^?1 dry matter intake) whose mean flows were not significantly different from each other. The mean endogenous ileal flows for amino acids other than lysine were higher (P < 0.05) for the EHC-fed pigs compared to the animals on the PF diet, except for proline, glycine and arginine. The similar endogenous ileal lysine excretion for pigs receiving a SAA-based diet and in positive body nitrogen balance, and PF-fed pigs in negative body nitrogen balance, indicates that negative body nitrogen balance per se does not lead to a lowered endogenous ileal excretion. It would appear, however, that the presence of dietary peptides or protein in the gut increases amino acid excretion at the terminal ileum above that found with PF or SAA alimentation. Consequently, endogenous ileal amino acid flow in the pig may be underestimated when determined by the traditional PF method.     

Evaluation of the isotope dilution technique for determining ileal endogenous nitrogen excretion in the rat

Three body amino acid pools (plasma free, plasma bound and small intestinal tissue) were evaluated as precursors to allow measurement using the isotope dilution technique of endogenous excretion at the terminal ileum of animals. Eighteen 150-g bodyweight rats were given either a protein-free, an enzyme-hydrolysed casein based or a synthetic amino acid based diet, and digesta were collected from the terminal ileum. The animals had been subjected to a constant 8-day infusion of tritiated leucine via subcutaneously implanted osmotic mini pumps. Specific activities (dpm nM^?1 leucine) of the ileal digesta and the plasma free, plasma bound and small intestinal tissue pools were determined and the specific activity for the ileal digesta was expressed as a proportion of the respective precursor pool value to give dilution factors for each dietary treatment. For the protein-free diet, where the ileal nitrogenous flow is endogenous by definition, the dilution factor for an appropriate precursor pool would be unity. For the hydrolysed casein and synthetic amino acid diets, in which the peptides and amino acids are expected to be virtually completely absorbed anterior to the ileum, high dilution factors (close to unity) would be expected. The mean dilution factors based on the plasma free amino acid pool were untenably low (0-2 to 0-3). For the plasma bound amino acid pool mean dilution factors of 1-3 were found for animals given the protein-free and synthetic amino acid diets, while a lower value (0-7) was obtained for the hydrolysed casein treatment. Untenably high factors (1-5) were found with the small intestinal tissue for the protein-free and synthetic amino acid treatments, while the corresponding value for the hydrolysed caseinfed rats was unity. The dilution factor data within treatments were highly variable, and none of the pools examined gave consistently reliable results and could thus be accepted as a valid precursor pool for the endogenous proteins.     

Effect of the duration of feeding of a protein‐free diet on endogenous ileal nitrogen and amino acid loss in the growing pig

The aim of the study was to determine whether endogenous nitrogen and amino acid excretions at the terminal ileum change over time in the growing pig fed a protein‐free diet for 8 days. Seven entire male pigs with an overall mean live weight of 81.6 kg (SEM 3.3 kg) and surgically implanted post‐valve T caecum cannulas were fed a semi‐synthetic casein‐based diet for 8 days. Food was withheld from the pigs for 24 h, after which they were fed a protein‐free diet for a further 8 days at a rate of 10% of metabolic body weight per day. Chromic oxide was included in the protein‐free diet as an indigestible marker. Ileal digesta were collected continuously from 13:00 to 18:00 h on each day of the experimental period. Endogenous ileal nitrogen flows were determined for each pig each day the protein‐free diet was given, and endogenous ileal amino acid flows for the first and eighth days. There were no significant (P > 0.05) effects of the duration of feeding of the protein‐free diet on endogenous ileal total nitrogen or amino acid flows, except for the amino acids glycine and cysteine, the flows of which significantly decreased over the 8 day period (P < 0.01 and P < 0.05 for glycine and cysteine respectively), from (mean ± SEM) 1639 ± 217 to 892 ± 212 µg g⁻¹ dry matter intake (DMI) for glycine and from 173 ± 13 to 127 ± 19 µg g⁻¹ DMI for cysteine. The relative contributions (moles of each amino acid as a proportion of total moles of amino acids) of threonine, glycine and cysteine decreased significantly (P < 0.05) and that of proline increased significantly (P < 0.05) during the 8 days that the protein‐free diet was fed to the pigs. © 2000 Society of Chemical Industry     

Rice Protein Isolates Produced by the Two Different Methods Lower Serum Cholesterol Concentration in Rats Compared with Casein

Highly purified rice protein isolates (RPI) were prepared by an alkaline extraction–acid precipitation method (E-RPI) and by an α-amylase treatment to remove starch (T-RPI). Biological values of these RPI were significantly lower than that of casein. Serum cholesterol concentrations were compared among groups of rats fed (per kg diet) 200, 300 or 400 g E-RPI, 400 g T-RPI, 250 or 400 g casein kg⁻¹ or 400 g soya bean protein isolate (SPI). With all the diets containing 400 g protein kg⁻¹ diet, growth rates of rats were the same. At this level, E-RPI, T-RPI and SPI diets produced significantly lower serum cholesterol concentrations than the casein diet. Faecal bile acid plus neutral steroid excre-tion was significantly higher in rats fed the 400 g kg⁻¹ T-RPI or 400 g kg⁻¹ SPIdiets compared with rats fed the 400 g kg⁻¹ casein diet. On the other hand, the 400 g kg⁻¹ E-RPI diet did not increase steroid excretion. Plasma cholesterol concentrations in rats fed diets with amino acid mixtures simulating SPI and E-RPI were also significantly lower than that of rats fed the diet with an amino acid mixture simulating casein even though the faecal excretions of total bile acids were the same amongst groups. These results support the view that RPI are hypocholesterolaemic relative to casein and at least the hypocholesterolaemic effects of E-RPI would be independent of interruption of the enterohepatic circulation of endogenous steroids.     

Effect of condensed tannin in cottonseed hulls on endogenous ileal amino acid loss in the growing rat

The effect of condensed tannin (CT) in cottonseed hulls (CSH) on endogenous ileal amino acid flow in the growing rat was evaluated. CSH contain around 900 g kg^?1 fibre and 52 g kg^?1 total CT. Twenty-four rats were allocated to four semi-synthetic diets, which contained enzymically hydrolysed casein (EHC) as the sole source of dietary nitrogen and chromic oxide as an indigestible marker. Two of the diets contained no CSH while the remaining two contained 50 g kg^?1 CSH. At each level of hull inclusion (0 and 50 g kg^?1), polyethylene glycol (PEG: MW 3500) was added (6 g kg^?1) to one of the diets. The effect of CT was assessed by determining endogenous ileal amino acid loss in the presence or absence of PEG, which binds and inactivates CT. The rats were given their respective experimental diets ad libitum for 14 days. Samples of digesta were collected at slaughter from the terminal 15 cm of ileum. The digesta samples were centrifuged and the supernate ultrafiltered. The precipitate plus retentate (MW > 10000) fraction affords an estimate of endogenous loss. Inclusion of CSH in the EHC based diet increased ileal flow of total nitrogen (1387 versus 1623 μgg^?1 dry matter intake; P ≤ 0.05), increased ileal flow of total amino acids (23%; P ≤ 0.01), and significantly increased ileal flow of several individual amino acids. There was no significant effect of PEG and no PEG × diet interaction; showing that the CSH effects could not be explained by action of CT. The presence of hulls in commercial cottonseed meal would appear to contribute to the reported low apparent ileal amino acid digestibility coefficients for cottonseed meal by increasing endogenous ileal amino acid flow, but this effect is not due to the CT component of the hulls.     

Composition of endogenous ileal digesta nitrogen from the rat—the use of distilled water for digesta collection

The composition of endogenous nitrogen (N) in digesta from the distal ileum of the growing rat was determined following the collection of digesta using different flushing media. Twelve growing rats were given a protein-free diet for 6 days, and samples of digesta were collected from the terminal 20 cm of ileum of each euthanased animal using either distilled water or physiological saline as the flushing medium. The digesta samples were centrifuged and the supernate was ultrafiltered. Nitrogen and amino acid contents were determined in the precipitate plus retentate (MW> 10000 Da) and ultrafiltrate (MW < 10000 Da) fractions, as well as urea, creatinine, ammonium and free amino acids in the ultrafiltrates. There was no significant effect of collection method on the levels of N-containing substances in rat endogenous ileal digesta.     

The effect of food dry matter intake on the flow of amino acids at the terminal ileum for rats fed an enzyme‐hydrolysed casein‐based diet

The aim of the study was to determine whether food dry matter intake had an effect on endogenous ileal amino acid flows in the rat when the flows were expressed in units of mg g^?1 dry matter. Eighty 200 g body weight rats were trained for 7 days to consume a casein‐based diet over a daily 3 h feeding period, and then an enzyme‐hydrolysed casein (MW < 5000 Da)‐based diet, with chromic oxide as an indigestible marker, was fed for a further 8 days. The mean ratio of food intake to metabolic body weight over all 80 rats was determined on days 11 and 12. On day 15, food was offered to groups of 10 rats at each of eight intake levels. The intake levels were calculated from the mean food intake value and individual metabolic body weights and scaled in increments of 0.1 by factors ranging from 0.3 to 1.0. Digesta were collected from the terminal ileum 3 h after the start of the meal, and endogenous ileal amino acid flows were determined after amino acid and Cr analyses of the diet and endogenous ileal digesta fractions prepared by centrifugation and ultrafiltration (10 000 Da molecular weight cut‐off). The linear regression relationships between ileal amino acid flows, expressed as mg g^?1 dry matter, and dry matter intakes demonstrated that all slopes were negative but that the slopes for nine of these amino acids were not significantly different from zero (P > 0.05). There were significant slopes (P < 0.05) for the other eight amino acids, although the magnitudes of the effect were small. When the data were re‐examined after removing the lowest feeding level, the slopes for most of these amino acids were no longer statistically significant. The results showed that the measures of amino acid flow (mg g^?1 dry matter), except for isoleucine and cystine, over a wide range of food intakes were not materially affected by food intake. From the perspective of bioassay logistics the results indicate that expressing ileal amino acid flows proportional to dry matter intake is justified over the range of intakes found in practice for determining true ileal amino acid digestibility by the enzyme‐hydrolysed casein method. © 2002 Society of Chemical Industry     

Ileal digestibility of defatted soybean,lupin and chickpea seed meals in cannulated Iberian pigs: I. Proteins

Five castrated male Iberian pigs (100 ± 2 kg body weight) fitted with T‐shaped cannulas at the terminal ileum were used to determine ileal digestibility of legume seed meals. The diets were based on defatted soybean, lupin or chickpea seed meals and contained similar levels of digestible energy (14.2–15.1 kJ g^?1) and protein (107 g kg^?1). Protein‐free and a hydrolysed casein diets were used to study endogenous ileal amino acid flows. Chromium oxide (10 g kg^?1 diet) was added to the diets as an indigestible marker. Ileal flows in pigs fed the hydrolysed casein diet were different (p < 0.05) in amino acid contents and composition from those on the protein‐free diet. Ileal sialic acid flows in pigs fed lupin‐ or chickpea‐based diets were higher (p < 0.05) than those of animals fed soybean or casein diets. Among essential amino acids, only the apparent ileal digestibilities of phenylalanine and valine in lupin meal were lower (p < 0.05) than those in soybean. Apparent ileal digestibilities of lupin aspartate and proline, together with chickpea aspartate, were also lower (p < 0.05) than those of soybean. True ileal digestibility of nitrogen in pigs fed lupin or chickpea meals, calculated according to values from animals fed the protein‐free diet, was lower (p < 0.05) than that for soybean or casein. Among individual essential amino acids, only the true ileal digestibility of phenylalanine in lupin was lower (p < 0.05) than that in soybean. True ileal digestibility of nitrogen calculated according to values obtained with pigs fed a hydrolysed casein diet was not different among soybean, lupin or chickpea meals. Among essential amino acids, only the true ileal digestibilities of isoleucine and lysine in chickpea were lower (p < 0.05) than those of soybean. It is concluded that true ileal nitrogen and amino acid digestibilities of lupin and chickpea meals are comparable to those of defatted soybean in Iberian pigs. The results with protein‐free diets tended to underestimate endogenous protein secretion in pigs fed on diets containing protein. Copyright © 2005 Society of Chemical Industry     

Endogenous lysine in ileal digesta in the growing rat determined using different methods

BACKGROUND: Endogenous lysine in ileal digesta has been determined directly using highly digestible proteins and hydrolysates and assuming a complete absorption of dietary amino acids. In this study, the endogenous lysine in the ileal digesta of rats fed casein was determined using the guanidination method (baseline) and directly (assuming complete digestion and absorption) for casein and a highly hydrolysed casein. The peptide alimentation/ultrafiltration technique was also used to determine the endogenous ileal lysine for the casein hydrolysate (Peptopro®). RESULTS: Mean endogenous ileal lysine for rats given the unguanidinated casein and determined directly assuming complete digestion and absorption (644 mg kg^?1 dry matter intake (DMI)) or for a highly hydrolysed casein with the same assumption (596 mg kg^?1 DMI) was significantly (P < 0.05) higher than the endogenous ileal lysine for casein determined using the guanidination method (274 mg kg^?1 DMI). The endogenous lysine in ileal digesta for a casein hydrolysate determined using the alimentation/ultrafiltration method (302 mg kg^?1 DMI) was not significantly (P < 0.05) different from that based on the guanidination method but was significantly (P < 0.05) lower than the equivalent endogenous lysine determined directly. CONCLUSION: Dietary amino acids are not completely absorbed from casein or its hydrolysate and determining endogenous amino acids in ileal digesta directly, assuming complete absorption, overestimates the amount of endogenous ileal amino acids. Copyright © 2009 Society of Chemical Industry     

Bioavailability of new synthesised glucooligosaccharides in the intestinal tract of gnotobiotic rats

Using germ-free rats and previously germ-free rats inoculated with a complex human flora (heteroxenic rats), the digestibility of new glucooligosaccharides (GOS) and the effect of the digestive flora on their fermentation were studied. The GOS were synthesized using a glucosyltransferase reaction and were composed of a mixture of mono- to heptasaccharides (degree of polymerisation (DP) from 1 to 7), with α-1,6 and α-1,2 linkages. In germ-free rats, two diets containing GOS (20 g kg^?1 diet and 40 g kg^?1 diet) were compared to a control diet containing sucrose. The extent of GOS digestion was about 20% and the major component, DP 5, was almost fully resistant to the action of endogenous enzymes. In heteroxenic rats, only GOS (20 g kg^?1 diet) was compared to the control diet. Gaseous H₂ and CH₄ excretions measured in a respiratory chamber significantly increased by GOS fermentation (1.8 and 2.9 times, respectively, P < 0.001). As compared to the control group, there were no modifications of the pH, short-chain fatty acids (SCFA), and lactic acid concentrations in the caecum of rats fed with the GOS diet, but there were changes of the SCFA profile, ie butyric, isobutyric and isovaleric acid proportions significantly decreased (P < 0.01), whereas the caproic acid proportion increased (P < 0.05). GOS appeared to be completely fermented. Changes in the gaseous excretion and in the SCFA profile suggest that the intake of a low amount of this new synthetised GOS led to some decrease in the proteolytic activity and in an enhancement of the glycolytic fermentation.     

The effect of food dry matter intake on endogenous ileal amino acid excretion determined under peptide alimentation in the 50 kg liveweight pig

The daily ileal excretion of amino acids was measured at different food dry matter intakes for the 50 kg liveweight pig under conditions of peptide alimentation. The experiment comprised two cross-over design trials each involving four pairs of entire male pigs fitted with simple T-cannulae at the terminal ileum and fed a hydrolysed casein semi-synthetic diet. Each pair of pigs received one of four sequences of food dry matter intake arranged in a Latin square design, namely 0.06, 0.08, 0.10 and 0.12 (Trial 1) and 0.05, 0.07, 0.09 and 0.11 (Trial 2) of metabolic body weight (W^0.75) day^?1. Each pig received the diet at its described level of intake for 8 days, with continuous 24 h collection of ileal digesta on the fifth and eighth days. Chromic oxide was included in the diet to permit correction of ileal flows to complete digesta collection. Pooled digesta from each pig at each level of dry matter intake were centrifuged and ultrafiltered and the high-molecular-weight fraction was analysed for amino acid and nitrogen contents. There were significant (P < 0.05) linear relationships between endogenous ileal amino acid, nitrogen and dry matter excretion (mg day^?1) and food dry matter intake (g day^?1) except for lysine, glutamic acid and phenylalanine which increased in a curvilinear manner (P < 0.05). The results indicate that dietary dry matter intake influences endogenous excretion from the ileum. The relationships, determined under physiological conditions, provide preliminary data on the magnitude of small intestinal amino acid loss in the young growing pig.     

Effect of low‐zinc status and essential fatty acids deficiency on the activities of aspartate aminotransferase and alanine aminotransferase in liver and serum of albino rats

The effects of dietary deficiencies of zinc and essential fatty acids (EFAs) or both on aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were investigated in young growing rats. Four groups of albino rats were fed diets deficient in either EFA (4% hydrogenated coconut oil) or zinc (6 ppm) or both. The control diet was adequate in EFA (4% soybean oil) and zinc (100 ppm). The feeding trial lasted eight weeks and the activities of AST and ALT were determined in the liver and serum. EFA deficiency had no significant (p > 0.05) effect on liver AST. However, zinc and the double deficiencies depressed AST activity in the organ. Deficiencies of EFA, zinc and their combination depressed ALT activity in the liver significantly (p < 0.05) with a concomitant increase recorded in the serum. The data suggested alteration in endothelial permeability of the plasma membrane and thus leakage of membrane constituents in the tissue studied. It is therefore considered that these deficient diets may affect liver tissue negatively in view of the role of these enzymes in amino acid metabolism.     

Development,amino acid utilization and cell allocation in bovine embryos after in vitro production in contrasting culture systems

The effects of protein-supplemented and protein-free media on amino acid uptake, protein synthesis and cell differentiation in bovine blastocysts were investigated. Four formulations of synthetic oviduct fluid were used. Each formulation was identified by the principal supplement: bovine serum albumin (0.4%, w/v); polyvinyl alcohol (0.3%, w/v); or either of two steer sera (10%, v/v). After zygote culture, blastocyst yields (day 7.5) were lowest in protein-free medium and highest in albumin-supplemented medium. Subsequent 12 h incubation in the presence of both essential and non-essential amino acids was used for the measurement of amino acid flux. All blastocysts released alanine but consumed aspartate (P < 0.001) and the extent was influenced by prior culture conditions. Aspartate uptake was lower in blastocysts produced in protein-free conditions (P < 0.05) than in blastocysts produced in albumin-supplemented conditions. Consumption indices for 16 other amino acids were not influenced by blastocyst source. Cell counts and hatching incidences were highest for albumin-supplemented blastocysts, but were similar among blastocysts from the protein-free and serum-dependent treatments. Crucially, the use of protein-free medium for zygote culture did not compromise resultant blastocysts in terms of either de novo protein synthesis ([3H]phenylalanine incorporation) or trophectoderm function (phenotype based on interferon-tau detection). Thus, although blastocyst yields were compromised after zygote culture in a protein-free (vis-à-vis albumin-supplemented) medium, amino acid flux was qualitatively conserved, and only quantitatively modified in the case of alanine and aspartate. Moreover, vital properties of blastocysts that were produced, including de novo protein synthesis and trophectodermal cell function, apparently were not adversely affected by protein deprivation.     

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

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

Digestive utilisation of protein and amino acids from raw and heated lentils by growing rats

The effect of autoclave treatment on the digestive utilisation of protein and amino acids from lentils was studied in growing rats. Twenty 3‐week‐old Wistar rats (mean live weight 59 ± 4.8 g) were fed two experimental diets (n = 10 rats per diet) consisting of raw lentils (Lens culinaris M, var vulgaris, cv magda‐20) (diet RL) or lentils autoclaved at 120 °C and 1 atm for 30 min (diet AL). An additional group of 10 animals was fed a low‐protein (4%) diet and used to estimate metabolic nitrogen and amino acid excretion. Autoclaving caused a 76% reduction in the levels of trypsin inhibitor activity, but failed to improve the faecal digestive utilisation of protein or total amino acids. Lowest essential amino acid true digestibility in diets RL and AL was found for cysteine (60.2 vs 60.1%) and methionine (68.9 vs 66.6%). The protein digestibility‐corrected amino acid score was 71.2 and 66.4% and the availability of sulphur amino acid‐corrected amino acid score was 57.1 and 52.1% for diets RL and AL respectively. Sulphur amino acids were the first limiting ones. Overall, autoclave treatment did not improve protein or total amino acid digestibility from lentils, but caused a significant improvement in leucine and lysine digestibility and a significant decrease in the digestive utilisation of tyrosine and methionine. © 2002 Society of Chemical Industry     

Effect of Oral and Parenteral N Nutrition vs N-Free Nutrition on the Endogenous Amino Acid Flow at the Ileum of the Pig*

Two methods were tested for suppressing the depressive effect of N-free diets on the digestive secretions in pigs: the blood perfusion of amino acids (AA) or the peptide alimentation method. In the latter, enzymically hydrolysed casein (EHC), composed of oligopeptides and free AA, was used as the source of nitrogen. The unabsorbed dietary N molecules were discarded from the ileal digesta by ultrafiltration or gel filtration, assuming that the endogenous fraction did not contain significant amounts of small molecules. The AA supply by blood perfusion had no effect on the ileal endogenous AA losses (8·0 g AA kg⁻¹ DM intake) in growing pigs (±50 kg), compared with the N-free diet alone (8·3 g), whereas the EHC supplementation significantly increased them (18·0 g). The increase was due to both endogenous and dietary N. The presence of unabsorbed dietary AA in the ileal digesta was confirmed by the AA profile of the soluble molecules with a very low molecular mass (<3 kDa), which was close to that of EHC. Both ultrafiltration (cut-offs of 3 or 10 kDa) and gel filtration methods, utilised to discard the remaining dietary molecules, also eliminated a significant proportion of endogenous AA.     

日粮类型及精粗比对舍饲育肥牦牛肉氨基酸和脂肪酸含量的影响

本试验旨在研究日粮精粗比对舍饲育肥牦牛肉中氨基酸含量和脂肪酸含量的影响。试验以麦洼公牦牛为研究对象,采用2×3交叉设计,日粮类型分别为玉米型日粮以及用裸大麦替代60%玉米型日粮,两种日粮由玉米和裸大麦-玉米分别与酒糟、苜蓿等混合而成,两种日粮的精料与粗料比例由低到高分别为3:7(低精料组)、4:6(中精料组)、5:5(高精料组)。试验选取36头年龄为4周岁、体重(143.98±21.01) kg、健康状况良好的麦洼公牦牛,按体重随机区组试验设计分为6个处理组,预饲期15 d,正试期180 d。试验结束后,所有牦牛全部屠宰,采集倒数第1与第2肋骨间背最长肌,测定肉样的常规营养成分、氨基酸以及脂肪酸。结果表明:日粮类型对背最长肌水分、粗蛋白(Crude protein,CP)、粗脂肪(Ether extract,EE)、粗灰分(Ash)的含量、氨基酸的组成和含量均无显著影响(p>0.05),日粮类型只对背最长肌C17:1有显著影响(p<0.05);日粮精粗比对氨基酸的组成和含量有显著影响(p<0.05),必需氨基酸占总氨基酸比例(EAA/TAA)和必需氨基酸占非必需氨基酸比例(EAA/NEAA)差异显著(p<0.05),并且随着精料比例越高,氨基酸含量越高;日粮精粗比的不同显著(p<0.05)影响了脂肪酸C18:0的含量,并且低精组和中精组的C18:0的含量显著高于高精组(p<0.05),但低精组与中精组差异不显著(p>0.05);低精组和中精组的SFA含量均显著高于高精组(p<0.05),但UFA均低于高精组(p<0.05)。低精组和中精组的UFA/SFA均显著低于高精组(p<0.05)。可见,日粮精粗比对牦牛肉的氨基酸和脂肪酸含量均具有改善作用,其中,日粮精粗比为5:5效果最好。