Dispensable Amino Acids Research Articles

Dietary electrolyte balance influences ileal endogenous amino acid losses in broiler chickens

The objective of the current study was to determine the effect of nitrogen-free diets formulated with 2 ratios of corn starch and dextrose and 2 levels of dietary electrolyte balance (DEB; calculated as Na + K – Cl−, in mEq/kg of diet) on ileal endogenous amino acid (EAA) losses in 48-d-old broiler chickens. On d 43, 240 broiler chickens were allotted to 4 dietary treatments with 6 replicate cages per diet in a completely randomized design. Each experimental diet was fed for 5 d (d 43–48). All diets were free of nitrogen with 2 ratios of corn starch-to-dextrose (0.31 and 1.04) and 2 levels of DEB (108 and 219 mEq/kg of diet). Final BW and BW loss between birds fed the 2 corn starch-to-dextrose ratios and between birds fed 2 levels of DEB were not different (P > 0.05). Birds fed the diet containing a high level of DEB consumed less (P < 0.05) feed than birds on the low-DEB diet. Birds on the high-corn starch-to-dextrose (1.04) diet showed a tendency for higher (P = 0.08) feed intake. High dietary dextrose level (corn starch-to-dextrose ratio of 0.31) resulted in higher (P < 0.05) ileal DM and energy digestibility. A high level of DEB resulted in higher (P < 0.05) ileal endogenous nitrogen loss. Arginine, Ile, Leu, Phe, Val, Ala, Glu, Gly, Pro, and Tyr secretion into the gut increased (P ≤ 0.05) with an increasing level of DEB. Endogenous His, Lys, Thr, Asp, Cys, and Ser showed a tendency for increased (P ≤ 0.1) losses with a high level of DEB. Mean ileal EAA losses for the indispensable and dispensable amino acids for the low-DEB diet were 81 and 82%, respectively, that of the birds fed the high-DEB diet. The 4 amino acids with the lowest endogenous flow were Met, His, Tyr, and Cys, whereas the highest endogenous flow was found in Glu, Asp, Val, and Leu. Data from the current study showed that EAA losses in the ileum of broiler chickens are significantly affected by DEB, but not by the ratio of corn starch to dextrose.

Excess leucine intake effects on asparagine synthetase and 3‐phosphoglycerate dehydrogenase expression in the liver of rats fed a low‐protein diet (820.13)

De novo synthesis of dispensable amino acids such as asparagine and serine is crucial for cell growth and function. We found that asparagine synthetase (AS), 3‐phosphoglycerate dehydrogenase (PHGDH, key enzyme for serine biosynthesis), and serine dehydratase (SDH, serine degradative enzyme) expression in rat liver were tightly regulated in response to the protein requirement. Thus, AS and PHGDH were induced through a low‐protein diet, below rat’s protein requirement, whereas SDH was induced through a high‐protein diet, above their requirement. However, we observed that SDH was also induced by leucine ingestion. Excess leucine intake through a low‐protein diet causes severe growth retardation in rat. We here examined the effect of dietary leucine on AS, PHGDH, and SDH expression with regard to growth retardation. Male rats were divided into 12 groups and fed for one week a diet containing low, moderate or high protein. Different levels of leucine (0, 2, 4, and 8%) were added to the diets. The results demonstrated that AS and PHGDH expression was dose‐dependently suppressed in rat liver, whereas SDH expression increased when rats were maintained on a low‐protein diet. Body weight and food intake concomitantly decreased. Valine and isoleucine affected neither gene expression nor food intake and body weight. These results suggested that leucine suppressed AS and PHGDH expression and could cause growth retardation.

Quality improvement of fish feed by using insulin-like growth factor 1 as a potential indicator of amino acid deficiency in yellowtail

Abstract We developed a new method for improving the quality of fish feed, by using insulin-like growth factor 1 (IGF1) as a potential indicator of dietary amino acid deficiency in yellowtail ( Seriola quinqueradiata ). First, 7 dispensable amino acid solutions (alanine, asparagine, cysteine, glutamine, glycine, serine and proline) and 0.9% NaCl (control) solution were injected into the dorsal muscle of fish using a syringe. Twenty-four hours post-administration, white muscle tissue was collected from the fish opposite to the injection site and assayed for igf1 mRNA expression. Only fish injected with proline showed a significant increase in igf1 mRNA expression levels. Subsequently, a feeding trial was conducted with 3 different diets—the control diet; the control diet supplemented with 1% proline; and the control diets supplemented with 3% proline. Juvenile yellowtails were fed exclusively with 1 of the 3 diets until apparent satiation. The body weight and feed efficiency were significantly higher in fish fed with the 3% proline-supplemented diet than fish fed with the control diet. Further, after 3 weeks, the expression levels of igf1 in white muscle and liver were significantly higher in fish fed with the 3% proline-supplemented diet than in fish fed with the control diet. Our results suggest that igf1 mRNA expression in the white muscle tissue of yellowtails serves as a reliable indicator of amino acid deficiency. Additionally, the results of our feeding trial suggest that proline is required for juvenile yellowtail growth. Moreover, white muscle igf1 may represent a valuable tool for improving the quality of fish feed.

Comparison of leucine requirement in olive flounder (Paralichthys olivaceus) by free or synthetic dipeptide forms of leucine

We report a promising dietary model for amino acid (AA) requirement studies in fishes. An eight-week feeding trial was carried out to compare the efficacy of free leucine (Leu) and dipeptide Leucinyl-Glycine (Leu-Gly) in diets for olive flounder. Growth performance and whole-body AA compositions were examined. Triplicate groups of fish (average weight, 0.27±0.001g) (23 fish per replicate) were fed seven isonitrogenous and isocaloric experimental diets containing 6 (basal), 9, 12 and 15g Leu/kg diet in the two different forms. The basal diet contained 6g Leu/kg from fish meal and the other six diets were prepared by adding 3g incremental levels of Leu or Leu-Gly. Growth rate was significantly (P<0.05) increased in the groups fed Leu-Gly in comparison to free Leu while no significant differences were observed by the supplementation level. Whole-body accumulations of most indispensable and dispensable AA were higher in the fish fed Leu-Gly, however, no significant differences were detected. A second-order polynomial regression analysis on the basis of weight gain revealed better utilization efficiency for Leu-Gly. Higher weight gain (0.63g) was obtained in fish fed Leu-Gly than fish fed Leu (0.55g). The results demonstrated that dipeptide Leu has higher efficiency in protein synthesis than free Leu and further confirmed that AA availability could be better in fish when fed dipeptide than free forms.

Free Amino Acids in Pacu, Piaractus mesopotamicus, Eggs and Larvae

AbstractFree amino acids (FAA) are used principally as substrate in protein synthesis and the source of energy in aerobic catabolism. In marine fish, embryo and larvae FAA are used to maintain body fluid osmolality during fish early development. However, there is essentially no information about FAA concentrations in early ontogeny of freshwater neotropical species in comparison to marine fishes. Therefore, the aim of this study was to evaluate the FAA concentrations in pacu, Piaractus mesopotamicus, eggs and larvae. Broodstock fish were induced to spawn and ovulated females were stripped of their eggs and immediately sampled for analysis. Larvae were sampled right after hatching (HL) and after the completion of the yolk‐sac absorption (YSA). The wet weight of the HL and YSA larvae amounted to 0.5 ± 0.1 mg and 1.1 ± 0.3 mg, respectively. HL larvae showed higher levels of most of the indispensable amino acids (IAA) in comparison to eggs and YSA larvae. Exceptions were observed with His and Trp that showed higher or similar levels, respectively, in YSA larvae. The FAA Orn, Tau, Glu, Gln, Gly, and Tyr increased concentrations in both larval stages while that of Tau was found in higher concentration in all analyzed stages. Also, the concentrations of Asn, Ala, Pro, Ser, and Asp were higher in HL larvae. Both larval stages displayed a rise in total free IAA/total free DAA (dispensable amino acids) ratio. The authors conclude that the highest level of FAA in HL pacu larvae is indicative of active proteolysis of yolk reserves and a probable catabolism regulation of some FAA through spare‐effect. In addition, Tau is one of the major FAA occurring during pacu ontogeny and may be performing regulation on body fluid osmolality regulation.

Ileal endogenous amino acid flow response to nitrogen-free diets with differing ratios of corn starch to dextrose in broiler chickens

An experiment was conducted to determine response in digestibility of DM and the AA composition of ileal endogenous flow of 26-d-old broilers to nitrogen-free diets (NFD) formulated with different ratios of corn starch to dextrose. A total of four hundred eighty 3-wk-old broiler chickens were used in a 4-d trial to estimate ileal endogenous flow (IEF) of amino acid (AA). The ratios of dextrose to corn starch investigated were 0:849, 283:566, 566:283, or 849:0 for diet numbers 1, 2, 3, or 4, respectively. All diets contained a calculated dietary electrolyte balance of 115 mEq/kg and chromic oxide (5 g/kg) as an indigestible marker. The birds received a standard starter diet from d 1 to 22 posthatch. On d 22 posthatch, all the birds were weighed and allocated to 4 treatments in a randomized complete block design. On d 26 posthatch, birds were asphyxiated with CO2 and ileal digesta was collected. Ileal DM digestibility was lowest in diet 1 (77.9%) and increased as the proportion of corn starch in the diet decreased. The IEF for all the indispensable AA were different (P < 0.01) among diets with the exception of Thr, which was not (P = 0.07). The respective IEF of AA (mg/kg of DMI) in birds fed diets 1, 2, 3, or 4 were 630, 664, 646, or 1,235 for Lys, 173, 172, 177, or 361 for Met, and 68, 74, 70, or 166 for Trp. For the dispensable AA and total AA, IEF of most AA except for Cys and Pro was highest (P < 0.01) in diet 4. Ileal endogenous flow of Pro was not different among diets. Diet 4 had the lowest (P < 0.01) IEF of Cys, whereas there was no difference among other diets. In conclusion, the data from the current study show that the variation in proportion of corn starch and dextrose in a nitrogen-free diet may affect estimates of ileal endogenous flows of N and AA.

Effects of autoclaving and sodium diformate supplementation to diets on amino acid composition, in vivo digestibility in mink (Neovison vison) and in vitro bioavailability using digestive enzymes from Atlantic salmon (Salmo salar)

The objective of the present experiment was to investigate effects of autoclaving and addition of sodium diformate to diets on amino acid (AA) composition, in vivo coefficient of total tract apparent digestibility (CTTAD) in mink (Neovison vison) of protein and AA and in vitro bioavailability of total AA using crude enzyme extracts from Atlantic salmon (Salmo salar). Diets were also evaluated for content of individual AA, reactive and available lysine, formic acid, pH and color analysis following autoclaving. The experimental treatments were organized according to a 4×2 factorial arrangement with four autoclave temperatures (100, 110, 120 and 130°C), without or with (10.6g/kg) sodium diformate. The CTTAD was determined for all experimental treatments, whereas the in vitro bioavailability was estimated only for the sodium diformate treatments at 100 and 130°C. Autoclaving at 130°C reduced (P<0.05) the dietary content of several AA, in particular arginine, cysteine, lysine and methionine. The CTTAD of crude protein and all individual AA and the in vitro bioavailability of AA were reduced (P<0.01) with increasing temperatures. Autoclaving also reduced the amount of reactive and available lysine (P<0.001), protein solubility (P<0.01) and increased (P<0.001) browning of the diets as measured by the CIE L* a* b* color model. Inclusion of sodium diformate reduced (P<0.05) the dietary content of several indispensable and dispensable AA. Supplemental sodium diformate did not affect CTTAD of crude protein and AA in mink; however, sodium diformate improved (P<0.05) the bioavailability of AA in the in vitro assay. Inclusion of sodium diformate reduced the amount of reactive lysine (P<0.05), protein solubility (P<0.05) and increased browning of the diets (P<0.001). In conclusion, autoclaving had negative effects on the CTTAD of protein in mink and on the in vitro bioavailability of AA. Supplemental sodium diformate did not affect CTTAD of protein in mink, but improved the in vitro bioavailability of AA when using digestive enzymes from Atlantic salmon.

Dietary protein source significantly alters growth performance, plasma variables and hepatic gene expression in rainbow trout (Oncorhynchus mykiss) fed amino acid balanced diets

The objective of the study was to evaluate the effect of dietary protein source on fish growth, nutrient utilization, plasma variables and hepatic gene expression in juvenile rainbow trout (Oncorhynchus mykiss). Fishmeal (FM) and soy protein isolate (SPI) were used as the main sources of protein in six isonitrogenous, isolipidic and isocaloric diets. The amino acid profiles of the diets were completely balanced to minimize differences between experimental treatments and formulated to contain increasing levels of branched-chain amino acids (BCAA) based upon dietary requirements for trout (NRC, 1993). Dietary protein source more consistently changed the measured variables while BCAA supplementation had an unexpected effect over whole body lipid content. Growth performance and protein retention efficiency were significantly reduced in fish fed SPI diets independently of BCAA supplementation. Total concentration of amino acids as well as circulating indispensable amino acids (IAA) were significantly elevated in the plasma of fish receiving SPI diets compared to fish fed FM diets. The change in IAA was large enough to increase (p<0.05) plasma IAA/DAA (DAA: dispensable amino acids) proportion even when the diets were formulated to have a ratio close to 1. Levels of circulating BCAA and alanine were also elevated in the fish fed SPI diets, possibly indicating a change in protein turnover. The use of SPI caused a reduction (p<0.05) in the hepatic expression levels of alanine amino transferase (alt1) and glutamine synthetase 2 (gls02), while an increase was observed for aspartate aminotransferase (got2), and asparagine synthetase (asns) compared with FM diets. Expression of the gene tor (target of rapamycin) declined over time for all treatments, while expression of a gene known to repress tor function, redd-1, was consistently higher in the liver of fish fed SPI diets. Glucose 6 phosphate dehydrogenase (g6pd) also showed a significantly higher expression in the liver of fish fed SPI diets but only at higher levels of BCAA supplementation.In summary dietary protein source has a significant effect over growth performance, body composition and hepatic gene expression in rainbow trout. We also identified for the first time in fish changes in the expression of redd-1, which may represent another regulatory point in the TOR cascade.

Interactive effects of age, sex, and strain on apparent ileal amino acid digestibility of soybean meal and an animal by-product blend in broilers

The objectives of this study were to determine if age, sex, and strain of broilers affect the apparent ileal amino acid digestibility (AID) of soybean meal and an animal by-product blend. Chicks from 2 broiler strains, 1 commercially available and the other in the test phase, were obtained from a common hatchery, feather-sexed, and placed into floor pens. The birds received common diets while on floor pens. Birds were transferred to metabolism crates for 2 ileal digestibility trials conducted at 3 and 6 wk of age. Two semipurified diets were formulated with each of the feed ingredients providing all of the amino acids (AA) in the diets. Diets were formulated to contain 20% CP, with chromic oxide added to the diet at 0.30% as the indigestible marker. The experimental diets were fed for a 72-h period after an overnight fast to 8 replicate cages of 5 birds per cage. Upon completion of the experimental periods (i.e., d 22 and 43), birds were euthanized and ileal digesta samples were collected and pooled by pen, frozen, lyophilized, and analyzed for AA and chromium concentrations. For soybean meal, no main effects were observed for age, sex, or strain; however, significant (P ≤ 0.05) 3-way interactions were observed for several dispensable and indispensable AA. Statistical analyses of these interactions indicate the AID of soybean meal may be different for 42-d males of the test strain. For the animal by-product blend, only main effects were significant for each AA, with the exception of Ile and Tyr. Main effect of strain was observed for most of the AA, showing that the commercially available strain had higher AID than the test strain. Also, significant main effect of age indicated that the AID for animal by-product blend was higher at 42 d than at 21 d. Evaluation of these 2 ingredients showed that age, sex, and strain may affect digestibility of feedstuffs and should be considered independently or interactively, for some cases, in future investigations as sources of variation in AA digestibility.

Sulfur amino acid metabolism and requirements

The sulfur amino acids (SAA) are methionine and cysteine. Methionine is indispensable.1–5 It donates its sulfur atom to cysteine during the process of trans-sulfuration, making cysteine a dispensable amino acid.6 The carbon skeleton of cysteine, however, is donated by serine.6 Methionine is metabolized via three major metabolic pathways: transmethylation, remethylation, and trans-sulfuration. It serves as the major methyl group donor in vivo,7,8 while cysteine is the rate-limiting substrate for the synthesis of the antioxidant glutathione (GSH).9–11 Both amino acids are important for protein synthesis. The total sulfur amino acid (TSAA) requirement, when fulfilled by the provision of methionine, can be significantly reduced only by adding cysteine to the diet. This phenomenon has been firmly established in animals12–15 and in humans16–18; it is consistent across the lifespan, having been observed in neonates,5–20 children,21 and adults.17,18 In the present issue of this journal, F. Jahoor examines the role the availability of sulfur amino acids plays in severe childhood undernutrition.22 The present editorial complements that work by providing an overview of SAA metabolism and requirements. ### Methionine In healthy adults, the metabolism of methionine is regulated toward anabolism23 in the fed state, and methionine flux is increased relative to that observed in the fasted state. Feeding results in decreased methionine release from protein breakdown and increased transmethylation, trans-sulfuration, and remethylation. In the fasted state, methionine utilization for protein synthesis is increased relative to transmethylation, resulting in the conservation of methionine when SAA availability is low. When SAAs are absent from the diet of healthy adults,17 methionine is used preferentially for protein synthesis relative to transmethylation, confirming previous findings that methionine is conserved via protein synthesis when SAA …

Ileal digestibility of crude protein, amino acids, dry matter and phosphorous in pigs fed diets steam conditioned at low and high temperature, expander conditioned or extruder processed

An experiment was designed to determine the effect of hydrothermal treatment (HT) on the coefficient of apparent ileal digestibilities (CAID) of crude protein (CP), amino acids (AA), starch and phosphorous (P) in growing pigs (initial body weight (BW) of 29.5±2.4kg) fitted with a T-cannula in distal ileum. The mash, based on wheat, fishmeal and soybean meal, was subjected to four HT, giving diets: (1) unconditioned mash as control; (2) low-temperature steam conditioning before pelleting (SC-Low); (3) high-temperature steam conditioning before pelleting (SP-High); (4) expander conditioning before pelleting (EXP); and (5) extruder processing (EXT). The diets were fed to five growing pigs allotted to treatments in a 5×5 Latin square design. The HT (average of four HT diets) increased CAID of starch (P=0.001), but did not affect that of DM, CP or P. The CAID for total indispensible AA was improved by HT processing (P=0.041), as were the CAID for Arg (P=0.018), Ile (P=0.044), Lys (P=0.006) and Thr (P=0.013), when compared to the control. For Lys, CAID was greater (P=0.006) for pigs fed the HT diets compared to the control and for the average of EXP and EXT compared to the average of SC-Low and SC-High. For dispensable AA, CAID were not affected by the treatments. In conclusion, HT increased ileal digestibility of starch, total IAA, Arg, Ile, Lys and Thr compared to a control diet fed as mash in growing pigs, with expander conditioning and extruder processing of particular merit for Lys.

The effects of supplementary bacterial phytase on dietary true metabolisable energy, nutrient digestibility and endogenous losses in precision fed turkeys

1. A total of 40 female BUT9 turkeys were used in a precision-feeding assay to investigate the effect of dietary phytase on true metabolisable energy corrected for N retention (TME N ), coefficients of true dry matter (TDMD), mineral, amino acid and nitrogen (TND) digestibilities and the excretion of endogenous mucin, measured as sialic acid (SA). 2. Five treatments were used in this study: control (C), C + 250 phytase units (FTU) per kg feed, C + 500 FTU, C + 2500 FTU, and glucose only for endogenous losses estimation. Diets were formulated to be nutritionally adequate with the exception that the P content was relatively low (3·6 g/kg non-phytate P). 3. Inclusion of phytase increased TND in a quadratic manner with the optimum being achieved at approximately 500 FTU, at which TND was 37 % greater than in the control. The concentration of SA in the excreta decreased linearly with increased phytase supplementation. Dietary TME N , TDMD and true mineral digestibility coefficients were not significantly affected by phytase supplementation. 4. Phytase inclusion increased digestibility coefficients for indispensable, dispensable and total amino acids in a linear manner. The scale of the response to phytase was greatest with threonine and least with lysine digestibility, suggesting a specific mechanism of action that benefits gut health. 5. The strong negative relationship between secretion of SA and threonine digestibility suggests that a large part of the threonine benefit may be from reduced mucin synthesis. This supports the hypothesis that dietary phytase may play a role in improving the health status of the intestine and, as a result, reduces the maintenance energy requirements of turkeys.

Selective Control of Oligosaccharide Transfer Efficiency for the N-Glycosylation Sequon by a Point Mutation in Oligosaccharyltransferase

Asn-linked glycosylation is the most ubiquitous posttranslational protein modification in eukaryotes and archaea, and in some eubacteria. Oligosaccharyltransferase (OST) catalyzes the transfer of preassembled oligosaccharides on lipid carriers onto asparagine residues in polypeptide chains. Inefficient oligosaccharide transfer results in glycoprotein heterogeneity, which is particularly bothersome in pharmaceutical glycoprotein production. Amino acid variation at the X position of the Asn-X-Ser/Thr sequon is known to modulate the glycosylation efficiency. The best amino acid at X is valine, for an archaeal Pyrococcus furiosus OST. We performed a systematic alanine mutagenesis study of the archaeal OST to identify the essential and dispensable amino acid residues in the three catalytic motifs. We then investigated the effects of the dispensable mutations on the amino acid preference in the N-glycosylation sequon. One residue position was found to selectively affect the amino acid preference at the X position. This residue is located within the recently identified DXXKXXX(M/I) motif, suggesting the involvement of this motif in N-glycosylation sequon recognition. In applications, mutations at this position may facilitate the design of OST variants adapted to particular N-glycosylation sites to reduce the heterogeneity of glycan occupancy. In fact, a mutation at this position led to 9-fold higher activity relative to the wild-type enzyme, toward a peptide containing arginine at X in place of valine. This mutational approach is potentially applicable to eukaryotic and eubacterial OSTs for the production of homogenous glycoproteins in engineered mammalian and Escherichia coli cells.

Physiological responses of Senegalese sole ( Solea senegalensis Kaup, 1858) after stress challenge: Effects on non-specific immune parameters, plasma free amino acids and energy metabolism

Physiological responses after an acute handling stress and their subsequent effects on innate immune parameters, plasma free amino acids (AA) and liver energy substrates were assessed in Senegalese sole ( Solea senegalensis). Eight groups of six specimens (136.1 ± 58.4 g wet weight) were maintained undisturbed, while other eight groups of six specimens were used for acute stress challenge (air exposed during 3 min). A group of six specimens was sampled for blood and head-kidney collection immediately after air exposure (time 0), while the remaining groups were sampled at 5 and 30 min, 1, 2, 4, 6 and 24 h. Undisturbed fish were sampled at the same times and used as control. Fish were fasted for 24 h prior to air exposure and sampling. Plasma cortisol, glucose, lactate and osmolality levels increased immediately after stress peaking at 1 h in air exposed fish. Changes in plasma free AA were also observed at 1 and 24 h after stress. In liver, glycogen levels significantly decreased at 30 min and 1 h, while triglycerides values significantly increased at 1, 2 and 4 h in air exposed fish. In addition, total AA levels in liver augmented significantly at 2 h holding high until 24 h in air exposed specimens. The respiratory burst of head-kidney leucocytes from air exposed fish was significantly higher than that from control groups at 2 and 6 h after air exposure. On the other hand, plasma lysozyme activity significantly decreased at 4 h after acute stress in air exposed fish, while plasma alternative complement pathway followed an inverse linear relationship with respect to cortisol showing the lowest value at 1 h after air exposure. The present study suggests that Senegalese sole presents a stress response comparable to that observed in other teleosts. While some indispensable AA may be used for the synthesis of compounds related to the stress response or fatty acid transport, dispensable AA were probably mainly employed either as energy sources or in gluconeogenesis. Moreover, results from non-specific immune parameters assessed suggest that cortisol may act as regulator of the innate immune system.

Assessment of dietary lysine requirement for silver perch ( Bidyanus bidyanus) juveniles

A 10-week rearing trial was conducted to assess the lysine requirement of juvenile silver perch, and to evaluate the effects of dietary lysine levels on the morphological measurements, body composition, hematological traits and muscle carnitine status of the fish. Seven isonitrogenous and isolipidic diets were formulated to contain multiple intact proteins and pre-coated crystalline amino acids. l-lysine HCl was supplemented to the experimental diets at the expense of a dispensable amino acid mixture to achieve lysine levels from 0.90 and 2.70% of dry diet. Each diet was randomly assigned to triplicate groups of 10 fish and was fed to apparent satiation five times daily. At the end of the trial, percent weight gain increased with increasing dietary lysine from 0.90% to 2.10%, then the value decreased slightly. A similar trend was observed in the feed efficiency, protein efficiency ratio, productive protein value and daily protein deposition. The condition factor, hepatosomatic index, intraperitoneal fat and viscerosomatic index were markedly affected by the dietary lysine level. Crude protein contents of the whole body, muscle and liver were significantly depressed in the fish fed lysine-deficient diets, while the whole body lipid content was higher in these fish. The hematocrit value, hemoglobin concentration and free lysine levels in plasma were lower in the silver perch given lower lysine diets. Although muscle carnitine status was not clearly affected by the dietary lysine level, the values of free carnitine and acid soluble carnitine tended to be lower in the fish fed lower lysine diets. Based on the quadratic broken-line model, the dietary lysine requirement for maximum growth of the silver perch juveniles was satisfied at 2.32% lysine in the dry diet, corresponding to 5.96% of the dietary protein. Furthermore, 2.06% of chemically available lysine in the diet (equivalent to 5.30% dietary protein) was required for the optimal growth of the fish.

Comparison of leucine and dispensable amino acid kinetics between Indian women with low or normal body mass indexes during pregnancy

Evidence suggests that in women with a normal to high body mass index (BMI; in kg/m(2)), the extra amino acids needed during pregnancy are met through reduced oxidation. It is not known whether a woman with a low BMI can make this adaptation successfully. The objective was to measure and compare leucine kinetic parameters and alanine-nitrogen, glutamine amide-nitrogen, and glycine and cysteine fluxes in Indian women with a low and normal BMI in early and midpregnancy. Fasted- and fed-state kinetics were measured by infusing 1-[(13)C]leucine, [(2)H(2)]cysteine, [(2)H(2)]glycine, [5-(15)N]glutamine, and [(15)N]alanine in groups of 10 women with a low BMI (<18.5) and 10 women with a normal BMI (18.5-25) in the first and second trimesters of pregnancy. Leucine, glutamine, glycine, and cysteine fluxes were faster in women with a low BMI in both trimesters, but there was no difference in alanine flux between groups. This difference was explained in the first trimester by a higher proportion of fat-free mass in low-BMI women. Leucine oxidation and percentage of dietary leucine oxidized were higher in low-BMI women in both trimesters, but nonoxidative disposal was not different between groups. Although they use dietary protein less efficiently, low-BMI women maintain net protein synthesis at the same rate as do normal-BMI women and produce similar quantities of labile nitrogen for the de novo synthesis of other dispensable amino acids such as glycine and cysteine. The extra amino acids required for increased maternal protein synthesis during pregnancy are provided by an overall decrease in amino acid catabolism in women with normal or low BMI.

Modulation of blackspot seabream (Pagellus bogaraveo) intermediary metabolic pathways by dispensable amino acids

The objective of the present work is to investigate the main metabolic pathways by which dispensable amino acids (DAA) are diverted towards lipid formation in blackspot seabream. For that purpose, a control diet was formulated to contain 45% of crude protein (7.2gN/100g dry matter) mainly supplied by fish meal (45P). In two other diets, 22.2% of the dietary nitrogen (1.6gN/100g dry matter) was replaced by an equivalent amount of nitrogen provided by two different mixtures of DAA: alanine and serine (diet AS) or aspartic and glutamic acid (diet AG). A fourth diet (diet 35P) only containing 35% of crude protein (5.6gN/100g dry matter) was included in order to analyze the possible additive effects of DAA. Compared to fish fed diet 35P, blackspot seabream appear to make a more efficient use of the nitrogen provided by alanine and serine than that provided by aspartic and glutamic acids in terms of growth. Contrary to fish fed AG, fish fed AS attained similar specific FAS activities as 45P fed fish, suggesting a further role of alanine and serine on this lipogenic pathway. Dietary nitrogen reduction (45P vs. 35P) or its replacement by a mixture of aspartic and glutamic acids (diet AG) were shown to up-regulate phosphoenolpyruvate carboxykinase (PEPCK) but without, however, any effect on plasma glucose levels. Dietary nitrogen level and nature seems to exert a complex regulation on energetic pathways through the gluconeogenesis/tricarboxylic acids cycle interaction.

First‐pass disappearance of cysteine in healthy adolescents

Cysteine (Cys), a dispensable amino acid serves as a precursor for some important substrates, such as glutathione and taurine. There are no data on Cys first‐pass disappearance in healthy children receiving cysteine by oral (PO) or intravenous (IV) route. We studied 10 healthy adolescents (age 15.8±1.8 y; wt 56.1±8.4 kg), receiving a 2‐day dietary period providing adequate energy and protein intakes. On day 3, subjects received a dual, primed, 6h, continuous tracer infusion of L‐13C‐ and L‐2H2‐Cys by the IV and PO routes randomly, while consuming small isocaloric and isonitrogenous meals every 30 min. The following day the route of tracer administration was reversed. The first‐pass disappearance of 13C‐ and 2H2‐Cys labels was 40.9±9.2% and 45.4±7.6 %, respectively, and there's no tracer effect (P = 0.11). Cys was oxidized to a greater extent by the PO route in contrast to the IV route (28 vs. 19%; P &lt; 0.01). True Cys flux determined by plasma ApoB‐100 enrichment was significantly higher when the tracer was given IV (P &lt; 0.001), suggesting that the splanchnic region is a major site of whole body cysteine utilization during the fed state. NIH DK‐62363, T32 HD‐007445, Ajinomoto 3‐ARP; USDA/ARS 25337387

Digestion rate of dietary starch affects systemic circulation of amino acids in weaned pigs

The present study was conducted to evaluate the in vitro and in vivo digestibility of dietary starch and its digestive behaviour on the systemic circulating amino acids (AA) in weaned pigs. Eighteen weanling pigs surgically fitted with a catheter in the jugular vein were randomly assigned to three dietary treatment groups. Sticky rice starch (SRS) was hydrolysed more quickly in vitro (P < 0.05) than maize starch (MS) and resistant starch (RS), and was almost completely hydrolysed within 4 h. The in vivo digestibility of dietary starch in different segments of the small intestine was significantly different. SRS was digested (81.9 %; P < 0.05) in the anterior jejunum, but not more than half of the MS and RS was digested in the same segment of the small intestine. The digestibilities of isoleucine, leucine, methionine, phenylalanine, threonine, tryptophan, valine, alanine, aspartate and serine in the SRS group were higher than in the MS group (P < 0.05), and all nutritionally indispensable and dispensable AA in the SRS group were higher when compared with those in the RS group (P < 0.05). The serum concentrations of nutritionally indispensable AA, proline and serine in the three groups were increased to a peak point within 1.5 h postprandially then decreased gradually; however, the time that serum concentrations of alanine, aspartate, glutamate and glycine in each group increased to a peak point was different. The concentrations of nutritionally indispensable AA, including arginine, cystine, histidine, isoleucine, leucine, methionine, phenylalanine, threonine, tryptophan, tyrosine and valine at 09.30 hours and arginine, cystine, histidine, isoleucine, methionine, phenylalanine, threonine, tryptophan, tyrosine and valine at 13.30 hours in the SRS group were higher than in the MS group (P < 0.05); all nutritionally indispensable AA in the SRS group were higher than in the RS group at 09.30 and 13.30 hours (P < 0.05), respectively. We conclude that dietary starches digested rapidly in vitro have higher digestibility in the anterior small intestine of pigs. Diets containing rapidly digestible starch ameliorate the digestive and absorptive function and regulate AA metabolism to beneficially increase the entry of dietary AA into the systemic circulation in pigs.

Standardized ileal amino acid digestibility in wheat distillers dried grains with solubles for broilers

A study was conducted to estimate the ileal digestibility of amino acids (AA) in 5 different samples of wheat distillers dried grains with solubles (DDGS) fed to broilers. Two hundred sixteen male Ross broiler chicks were fed a commercial starter diet from d 1 to 15 of age followed by the test diets from d 15 to 21. The 5 test diets consisted of a DDGS sample or wheat as the sole source of AA, dextrose, minerals, and vitamins. Chromic oxide (0.3%) was included in all diets as a digestibility marker. Each test diet was randomly assigned to 6 replicate cages, each with 6 birds. On d 21, birds were killed to sample ileal digesta for determining the apparent (AID) and standardized (SID) ileal AA digestibilities. The SID values were calculated using ileal endogenous AA losses previously determined in our laboratory. Among the indispensable AA in wheat DDGS, the lowest and highest AID average values were observed for Lys (35.6%) and Phe (79.2%), respectively. The most variable AID estimates of wheat DDGS samples were observed for Lys (24.4 to 45.7%), Thr (48.2 to 60.9%), and His (57.4 to 69.1%) as indispensable and Asp (32.5 to 50.9%), Gly (49.6 to 63.1%), and Ala (53.6 to 66.8%) as dispensable AA, respectively. Apparent ileal digestibility estimates of the wheat sample for Lys, Thr, His, Gly, and Ala were 77.5, 74, 83.6, 79.3, and 78.9%, respectively. All AA digestibility estimates for both AID and SID determined in wheat were higher than in wheat DDGS samples (P < 0.05). Considering both AID and SID coefficients of wheat DDGS samples, Lys was the least digestible AA, averaging 35.6 and 40.0%, respectively. Using SID values in practical diet formulation can increase accuracy, prevent overformulation of diets, and reduce cost of safety margins.