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Abstract Background Research on low-protein-level diets has indicated that even though the profiles of essential amino acids (EAAs) follow the recommendation for a normal-protein-level diet, broilers fed low-protein diets failed to achieve productive performance compared to those fed normal diets. Therefore, it is imperative to reassess the optimum profile of EAAs in low-protein diets and establish a new ideal pattern for amino acid balance. Furthermore, identifying novel sensitive biomarkers for assessing amino acid balance will greatly facilitate the development of amino acid nutrition and application technology. In this study, 12 dietary treatments [Con(+), Con(-), L&A(-), L&A(+), M&C(-), M&C(+), BCAA (-), BCAA(+), Thr(-), Thr(+), Trp(-) and Trp(+)] were established by combining different EAAs including lysine and arginine, methionine and cysteine, branched-chain amino acid (BCAA), threonine, and tryptophan to observe the growth and development of the broiler chickens fed with low-protein-level diets. Based on the biochemical parameters and untargeted metabolomic analysis of animals subjected to different treatments, biomarkers associated with optimal and suboptimal amino acid balance were identified. Results Growth performance, carcass characteristics, hepatic enzyme activity, serum biochemical parameters, and breast muscle mRNA expression differed significantly between male and female broilers under different dietary amino acid patterns. Male broilers exhibited higher sensitivity to the adjustment of amino acid patterns than female broilers. For the low-protein diet, the dietary concentrations of lysine, arginine, and tryptophan, but not of methionine, cystine, or threonine, needed to be increased. Therefore, further research on individual BCAA is required. For untargeted metabolomic analysis, Con(+) was selected as a normal diet (NP) while Con(-) represented a low-protein diet (LP). L&A(+) denotes a low-protein amino acid balanced diet (LPAB) and Thr(+) represents a low-protein amino acid imbalance diet (LPAI). The metabolites oxypurinol, pantothenic acid, and D-octopine in birds were significantly influenced by different dietary amino acid patterns. Conclusion Adjusting the amino acid profile of low-protein diets is required to achieve normal growth performance in broiler chickens fed normal-protein diets. Oxypurinol, pantothenic acid, and D-octopine have been identified as potentially sensitive biomarkers for assessing amino acid balance.

Background: Research on low-protein-level diets has indicated that even though the profiles of essential amino acids (EAAs) follow the recommendation for a normal-protein-level diet, broilers fed low-protein diets failed to achieve productive performance compared to those fed normal diets. Therefore, it is imperative to reassess the optimum profile of EAAs in low-protein diets and establish a new ideal pattern for amino acid balance. Furthermore, identifying novel sensitive biomarkers for assessing amino acid balance will greatly facilitate the development of amino acid nutrition and application technology. In this study, 12 dietary treatments [Con(+), Con(-), L&A(-), L&A(+), M&C(-), M&C(+), BCAA (-), BCAA(+), Thr(-), Thr(+), Trp(-) and Trp(+)] were established by combining different EAAs including lysine and arginine, methionine and cysteine, branched-chain amino acid (BCAA), threonine, and tryptophan to observe the growth and development of the broiler chickens fed with low-protein-level diets. Based on the biochemical parameters and untargeted metabolomic analysis of animals subjected to different treatments, biomarkers associated with optimal and suboptimal amino acid balance were identified. Results: Growth performance, carcass characteristics, hepatic enzyme activity, serum biochemical parameters, and breast muscle mRNA expression differed significantly between male and female broilers under different dietary amino acid patterns. Male broilers exhibited higher sensitivity to the adjustment of amino acid patterns than female broilers. For the low-protein diet, the dietary concentrations of lysine, arginine, and tryptophan, but not of methionine, cystine, or threonine, needed to be increased. Therefore, further research on individual BCAA is required. For untargeted metabolomic analysis, Con(+) was selected as a normal diet (NP) while Con(-) represented a low-protein diet (LP). L&A(+) denotes a low-protein amino acid balanced diet (LPAB) and Thr(+) represents a low-protein amino acid imbalance diet (LPAI). The metabolites oxypurinol, pantothenic acid, and D-octopine in birds were significantly influenced by different dietary amino acid patterns. Conclusion: Adjusting the amino acid profile of low-protein diets is required to achieve normal growth performance in broiler chickens fed normal-protein diets. Oxypurinol, pantothenic acid, and D-octopine have been identified as potentially sensitive biomarkers for assessing amino acid balance. [ABSTRACT FROM AUTHOR]

According to the theory of animal nutrition, the nutritional requirements of aquatic animals for feed protein and amino acids are the minimum requirements for feed protein and amino acids under the conditions of meeting animal growth performance and physiological health. The high crude protein content in aquatic feed not only violates animal nutrition theory, but also causes serious waste of feed resources, and significantly increases the nitrogen input into aquaculture water bodies. Therefore, it is necessary to develop low protein content and high-quality aquatic feed. This type of feed industry can be referred to as low protein aquatic feed that achieves the ideal protein model. The ideal protein model for aquatic animals is calculated and formulated based on the amount of digestible protein and amino acids in the feed, while also maintaining good amino acid balance. Constructing a database of protein and amino acid digestibility in feed raw materials is the technical core for developing ideal protein models for aquatic feed. The use of industrial enzymatic hydrolysis technology and microbial fermentation technology can significantly improve the digestibility and utilization of protein and amino acids in feed materials, or develop new feed materials with high digestibility of protein and amino acids. The application of such raw materials in feed is an important guarantee for the development of low protein content and high-quality aquatic feed. The quality standards for aquatic feed products are an important technical guarantee for the development of the aquatic feed industry and aquaculture industry. Therefore, the quality standards for aquatic feed products should also increase the technical indicators and content of digestible protein and amino acids in feed. [ABSTRACT FROM AUTHOR]

As a crucial staple crop in agricultural production, maize is extensively cultivated worldwide and plays a pivotal role in ensuring global food security. However, the significant deficiency of essential amino acids (EAA) and conditionally essential amino acids (CEAA), such as lysine (Lys), tryptophan (Trp), methionine (Met), and cysteine (Cys), leads to an imbalance of amino acids in the grain. This study investigates the regulatory mechanism of sulfur (S) application for regulating the amino acid balance of maize grains. The results demonstrate that S application has substantial effects on both the maize yield and nutritional quality. The S application resulted in an increase in maize yield by simultaneously enhancing the grain number per ear (GN) and 100-grain weight (GW), while S application elevated protein concentration through the augmentation of Cys concentration in maize grains. Furthermore, the Cys in grains optimizes the amino acid balance by regulating the ratio of other amino acids, thereby enhancing the nutritional quality of maize while ensuring a steady increase in protein concentration, simultaneously. Overall, the S application at 60–90 kg ha−1 synergistically improved both the yield and nutritional quality of maize, meeting the requirements for sustainable development in maize production. The findings offer a novel theoretical foundation and nutrient management approach for achieving high-yield and superior-quality maize production. [ABSTRACT FROM AUTHOR]

Feeding diets with an unbalanced amino acid (AA) profile can reduce the postprandial AA utilization for protein synthesis. Growing pigs use dietary AA mainly for protein accretion, whereas non-lactating and non-pregnant adult pigs use AA mainly for maintenance. The requirement for AA for growth is much larger than that for maintenance and growing pigs may therefore be more affected by a diet with an unbalanced AA profile than adult pigs. This study aimed to compare the postprandial plasma AA and metabolite concentrations of adult and growing pigs after feeding a diet with either an unbalanced (UNB) or a balanced AA profile (BAL). The postprandial plasma concentrations of AA were used to study the influence of AA balance on postprandial AA metabolism. Extensively hydrolysed feathers (EHF) were used as an AA source. Both BAL and UNB contained EHF supplemented with L-Ala, L-Asp, L-Glu, Gly, and L-Trp while BAL was also supplemented with L-His, L-Ile, L-Lys, L-Met, and L-Tyr. Four growing and four male adult pigs were fitted with a jugular catheter and received each diet as a meal test thrice. The meal test consisted of giving a small meal after an overnight fast followed by serial blood collection for 360 min. A non-linear regression model was used to describe the postprandial plasma AA kinetics. Plasma kinetics of adult and growing pigs fed BAL resulted in a higher area under the curve (AUC) for the AA that were used to balance the diet. For the other AA, feeding BAL resulted in lower AUC, suggesting faster metabolic utilization of AA for protein synthesis. The apparent quantity of dietary AA appearing in the plasma after feeding was lower in adult pigs, suggesting higher first-pass AA utilization in the intestine and liver. For adult and growing pigs, balancing the AA profile of the diet resulted in faster overall metabolic utilization of AA as seen in the generally lower AUC of BAL compared to UNB.

This study was conducted to investigate the effects of substitution of dietary fishmeal (FM) by compound plant protein supplemented with essential amino acids on growth performance, plasma physiology, and muscle growth-related genes of gibel carp (Carassius auratus gibelio). Four diets with equal digestible protein were prepared, where 30FM (control feed) contained 30% FM and land animal protein as a protein source, 10FM contained 10% FM, PMAa contained full plant meal (PM) supplemented with crystalline amino acid, and PM contained full PM feed. There was no significant difference in the specific growth rate (SGR) with 30FM, 10FM, and PMAa diets (p > 0.05); however, the SGR of PM group was the lowest with significant difference (p < 0.05). Feed efficiency of the PM group was the lowest with significant difference (p < 0.05). The whole-body crude protein content of fish in PMAa group was significantly higher than that in each group with additional FM (p < 0.05). There were no significant differences in plasma total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) or low-density lipoprotein cholesterol (LDL-C), and free amino acid profile of 30FM, 10FM, and PMAa groups (p > 0.05); however, they were significantly higher than that in PM group (p < 0.05). The expression of key genes in the TOR signaling pathway (tor, s6k1, 4e-bp2, and eif4e), autophagy (ulk1 and atg13), and ubiquitin–proteasome (trim63 and znrf2) system of the PMAa group was similar to that of the FM group (p > 0.05), indicating that the muscle growth-related biomarker genes were positively regulated by the appropriate dietary amino acid composition at the transcriptional level. These results suggest that FM in gibel carp diet can be totally replaced by PM without negative impact on growth performance and muscle growth-related biomarkers at the transcriptional level, which provided the requirement of digestible protein and balanced amino acid profile is satisfied.

We are experiencing an increase in the availability of protein ingredients from more sustainable production sources, and we need to learn how to utilize them to create highly nutritional and climate friendly foods. Much work is needed to assist in innovation, by developing principles leading to the design of the best structures to ensure optimal function. We propose a holistic approach to the design of new sustainable proteins for food, so that they may compare favorably to their animal sourced counterparts. While the immediate challenges are related to improving processing functionality and providing the essential amino acids balance, we will soon also need to learn to pay close attention to the molecular interactions occurring during processing, as these can be modulated to form different supramolecular structures. This shift will create new opportunities to innovate and create a new generation of highly nutritious and functional foods. This review focuses on the recent trends on the use of plant protein blends, and highlights the research gaps and challenges related to using ingredients of different composition and history to develop more climate friendly foods. • Protein quality, digestibility, bioavailability are related to processing conditions. • Control of proteins' supramolecular structures through processing is an opportunity to improve their functionality.. • The effect of structures formed during digestion in plant protein blends need to be understood. [ABSTRACT FROM AUTHOR]

In order to control and optimize chicken quality products, it is necessary to improve the description of the responses to dietary amino acid (AA) concentration in terms of carcass composition and meat quality, especially during the finishing period. The aim of this study was to investigate the effects of Lysine (Lys, i.e. a limiting AA used as reference in AA nutrition) and AA other than Lys (AA effect). In total, 12 experimental diets were formulated with four levels of digestible Lys content (7, 8.5, 10 and 11.5 g/kg) combined with either a low (AA−), adequate control (AAc) and high (AA+) amount of other essential AA (EAA) expressed as a proportion of Lys. They were distributed to male Ross PM3 from 3 to 5 weeks of age. No significant AA×Lys interaction was found for growth performance or carcass composition. Body weight and feed conversion ratio were significantly improved by addition of Lys but were impaired in broilers receiving the AA− diets, whereas breast meat yield and abdominal fat were only affected by Lys. No additional benefit was found when the relative amount of other EAA was increased. There was a significant AA×Lys interaction on most of the meat quality traits, including ultimate pH, color and drip loss, with a significant effect of both AA and Lys. For example, AA− combined with reduced Lys level favored the production of meat with high ultimate pH (>6.0), dark color and low drip loss whereas more acid, light and exudative meat (

This 45‐day work aimed to determine the response of juvenile pacu (Piaractus mesopotamicus) to balanced digestible protein (BDP) and to use these responses to determine whether the optimum economic levels of BDP would differ depending on the form in which the fish is sold. Six isoenergetic diets containing 163, 201, 238, 272, 315 and 348 g/kg BDP (dry‐matter basis) were prepared through the serial dilutions of a high‐protein diet with the low‐protein diet. Fish (initial average body weight, 10.82 ± 0.14 g) were fed with respective experimental diets three times a day until apparent satiation. The optimum biological level of BDP was calculated as 326 g/kg (dry‐matter basis) by the quadratic regression model for maximum body weight gain of juvenile pacu. To maximize economic returns (US$/kg) for different end products, the optimum economic levels of BDP were calculated as 311, 317 and 319 g/kg (dry‐matter basis) by an economic model for whole‐body, eviscerated and sliced juvenile pacu respectively. This finding revealed that obtaining maximum biological performance of fish in the case of high feed costs or low prices of the end product in consumer market would substantially reduce the economic returns. [ABSTRACT FROM AUTHOR]

The fractional composition of proteins of the cod-fish family - polar cod ( Boreogadus saida ) and blue whiting ( Micromesistius poutassou ) which are currently underutilized in the food industry has been studied. A method of multiple extraction of homogenized fish raw material with solutions of increasing ionic strength and pH was used for protein fractionation. Water-soluble (WSP), salt-soluble (SSP) and alkaline-soluble (ASP) fractions of fish proteins have been separated. The content of protein in a whole fish and its aqueous extracts was determined by the Kjeldahl method as well as photometric method. The amino acid composition of the proteins was studied by high-performance liquid chromatography. Protein of blue whiting comprises 92% of WSP and SSP fractions; while polar cod comprisesonly 60%. All proteins under study contain the full set of the amino acids including essential ones. The content of lysine both in non-fractionated proteins contained in a whole fish and their fractions is considerable (from 59.5 to 121 g kg-1). When evaluating the biological value of proteins, their usefulness is established (there are no limiting amino acids). The data of the rationality coefficient Rc which presents the balance of the amino acid composition of the proteins indicate the high biological value of proteins of the whole polar cod and their ASP fraction. The fish species being studied can be used for production high-grade protein products - fish hydrolysates and isolates. The possibility of using unrefined fish is shown that is peculiarity of novel food technologies for obtaining protein products of high biological value.

In order to control and optimize chicken quality products, it is necessary to improve the description of the responses to dietary amino acid (AA) concentration in terms of carcass composition and meat quality, especially during the finishing period. The aim of this study was to investigate the effects of Lysine (Lys, i.e. a limiting AA used as reference in AA nutrition) and AA other than Lys (AA effect). In total, 12 experimental diets were formulated with four levels of digestible Lys content (7, 8.5, 10 and 11.5 g/kg) combined with either a low (AA−), adequate control (AAc) and high (AA+) amount of other essential AA (EAA) expressed as a proportion of Lys. They were distributed to male Ross PM3 from 3 to 5 weeks of age. No significant AA×Lys interaction was found for growth performance or carcass composition. Body weight and feed conversion ratio were significantly improved by addition of Lys but were impaired in broilers receiving the AA− diets, whereas breast meat yield and abdominal fat were only affected by Lys. No additional benefit was found when the relative amount of other EAA was increased. There was a significant AA×Lys interaction on most of the meat quality traits, including ultimate pH, color and drip loss, with a significant effect of both AA and Lys. For example, AA− combined with reduced Lys level favored the production of meat with high ultimate pH (>6.0), dark color and low drip loss whereas more acid, light and exudative meat (<5.85) was produced with AA+ combined with a low Lys level. In conclusion, growth performance, carcass composition and meat quality are affected by the levels of dietary Lys and AA in finishing broilers. In addition, interactive responses to Lys and AA are found on meat quality traits, leading to great variations in breast pHu, color and drip loss according AA balance or imbalance. [ABSTRACT FROM AUTHOR]

An 8‐week feeding trial was conducted to evaluate the effect of replacement of dietary fishmeal with cottonseed meal (CSM) on the growth performance and health status of juvenile grass carp, Ctenopharyngodon idellus (6.67 g). Six isonitrogenous and isoenergetic diets were formulated with different CSM levels (0, 121, 241, 362, 482 and 603 g/kg diet). The first limiting amino acid was methionine, which decreased with an increase in dietary CSM from 361 to 538 g/kg. When the dietary CSM content was lower than 241 g/kg, the limiting amino acid was histidine. Thermal growth coefficient (TGC) and feed efficiency first increased and then decreased (p < 0.05), which was consistent with the change in the limiting amino acid. The feeding rate increased with a rise in the dietary CSM level (p < 0.05). The activity of digestive enzymes except trypsin decreased significantly (p < 0.05), serum aminotransferase activity and triglycerides increased, serum cholesterol decreased (p < 0.05). When dietary CSM was raised to 362 g/kg, intestinal villi and hepatopancreas tissue were injured. When the dietary CSM was 603 g/kg, alternative complement pathway haemolytic activity was inhibited (p < 0.05). The gossypol level in dorsal muscles from each treatment was below the detection limit. Based on the quadratic regression analysis of the TGC, the optimal dietary CSM level was 175.9 g/kg, and the maximum could be up to 351.8 g/kg and still result in the same TGC as that of control group. [ABSTRACT FROM AUTHOR]

One way to solve the problem of balancing the chemical composition of minced meat semi-finished products is the integrated use of raw materials of animal and vegetable origin. The purpose of the research is the development of formulations and determination of nutritional value of minced meat semi-finished products with oilseeds. The chemical composition of sesame seeds, sunflower seeds, and pumpkin seeds has been studied and the possibility of their use in the manufacture of semi-finished minced meats has been revealed. The formulae of minced meat semi-finished products, in terms of functional-technological and organoleptic properties, have been developed with optimum ratio of plant and animal components. Total organoleptic evaluation of the samples has shown a positive trend. Taste, smell, texture and overall evaluation have been improved. A slight reduction of the criterion for chemical composition of semi-finished products compared with that of a control sample has been found. It has been caused by the change of protein : fat : solids balance with the increase of vegetable fat and protein. The studied samples are characterized by a more balanced amino acid composition: the increase in SCOR and efficiency ratios is marked. The index of comparable redundancy is reduced, indicating a more complete use of the essential amino acids of minced meat semi-finished products for anabolic purposes. The developed samples meet the daily requirement for a number of essential nutrients by 11 - 64%. The content of vitamins A, B1 and E in the finished product containing sunflower seeds, that of magnesium and calcium in the sample containing sesame seeds, and 1.5 - 2 times increase of iron and zinc content enhance their nutritional value and allow classifying the samples as fortified foods.

We recently reported that plasma albumin redox state, which correlates with albumin synthesis rate, could be associated with the quality of dietary protein. Aiming to elucidate the association between them, plasma albumin redox state was investigated in rats fed various kinds of AIN-93G-based low protein diets. Plasma albumin redox state was shifted to a more oxidized state in rats fed 3% casein (CN) diet than those fed 3% whey protein or 3% wheat gluten diet, while supplementing 3% CN diet with cystine reversed it to a more reduced state, indicating that cystine would complement the shortage of cysteine in CN, thereby increasing albumin synthesis rate. Supplementation with glutathione, a cysteine-containing antioxidative tripeptide, normalized hepatic glutathione redox state modulated by ingestion of 3% CN diet, but it only reversed the oxidized shift of plasma albumin redox state to an extent similar to cystine alone or the constituting amino acid mixture of glutathione (i.e., glutamic acid, cystine, and glycine), indicating that glutathione would primarily serve as a source of cysteine rather than exert its antioxidative activity. Plasma albumin would thus be influenced by amino acid balance in dietary proteins, and it could be useful as a biomarker that contributes to prevention of protein under-nutriton, caused by not only insufficient protein intake but also ingestion of poor-quality protein.

Amino acid requirements can be studied maintaining or not the ratio of the amino acids to lysine and changing or not dietary crude protein level. A third alternative was studied in this study conducted to evaluate broiler performance and weight gain of carcass parts, in response to increasing dietary digestible lysine (dig Lys) levels (0.70, 0.80, 0.90, 1.00, 1.055, 1.11, 1.165, and 1.22%). Two basal diets were formulated to contain 19.0% (diet A) and 20.5% (diet B) crude protein, and Met, Arg and Thr levels were formulated to maintain their ideal ratio to Lys. Three hundred and twenty CobbXCobb500 broilers, from 19 to 40 days of age, were used. Basal diet A was set for the 4 lowest levels of dig Lys, and diet B for the other four levels. Body weight (BW), weight gain (WG), feed intake, Lys intake, feed conversion (FC), carcass part weights and carcass, breast, leg, and thigh protein and fat were evaluated. Body weight, WG and Lys intake linearly increased with increasing dietary dig Lys, independently of basal diet CP content. A multiple regression effect was observed for FC, with the best estimated levels of dig Lys of 0.96% and 1.18% for diet A and B, respectively. Breast and carcass weight gain and breast protein and water gain showed multiple regression and split curves as a function of basal diet. The best responses were obtained with the highest crude protein level in the basal diet. Therefore, we concluded that high levels of crude protein in basal diets are recommended to study amino acid requirements for broilers.

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• Unbalanced dietary amino acids affect plasma postprandial amino acid concentrations. • Postprandial plasma amino acid kinetics was used to study amino acid metabolism. • Modelling postprandial amino acid kinetics allows estimation of first metabolism. • Higher first-pass amino acid metabolism of adult pigs compared to growing pigs. • Faster decline of plasma amino acid concentrations when feeding a balanced diet. Feeding diets with an unbalanced amino acid (AA) profile can reduce the postprandial AA utilization for protein synthesis. Growing pigs use dietary AA mainly for protein accretion, whereas non-lactating and non-pregnant adult pigs use AA mainly for maintenance. The requirement for AA for growth is much larger than that for maintenance and growing pigs may therefore be more affected by a diet with an unbalanced AA profile than adult pigs. This study aimed to compare the postprandial plasma AA and metabolite concentrations of adult and growing pigs after feeding a diet with either an unbalanced (UNB) or a balanced AA profile (BAL). The postprandial plasma concentrations of AA were used to study the influence of AA balance on postprandial AA metabolism. Extensively hydrolysed feathers (EHF) were used as an AA source. Both BAL and UNB contained EHF supplemented with L-Ala, L-Asp, L-Glu, Gly, and L-Trp while BAL was also supplemented with L-His, L-Ile, L-Lys, L-Met, and L-Tyr. Four growing and four male adult pigs were fitted with a jugular catheter and received each diet as a meal test thrice. The meal test consisted of giving a small meal after an overnight fast followed by serial blood collection for 360 min. A non-linear regression model was used to describe the postprandial plasma AA kinetics. Plasma kinetics of adult and growing pigs fed BAL resulted in a higher area under the curve (AUC) for the AA that were used to balance the diet. For the other AA, feeding BAL resulted in lower AUC, suggesting faster metabolic utilization of AA for protein synthesis. The apparent quantity of dietary AA appearing in the plasma after feeding was lower in adult pigs, suggesting higher first-pass AA utilization in the intestine and liver. For adult and growing pigs, balancing the AA profile of the diet resulted in faster overall metabolic utilization of AA as seen in the generally lower AUC of BAL compared to UNB. [ABSTRACT FROM AUTHOR]

Abstract: Samples of pork longissimus muscle (n=16) cooked to either 60°C or 75°C in a water bath for 90min were assessed for amino acid composition. Recovery of protein in the cooked meat plus the cooking juice was >93% and was slightly higher at 60°C (P=0.031), but retention in the meat was only 89% and 82% for the lower and higher temperatures (P<0.0001). Individual amino acids varied in recovery and retention with retention being particularly low for taurine and histidine. The balance of indispensable amino acids was less than ideal, with leucine and valine being the limiting amino acids by about 30% for both raw and cooked pork. Cooking had no detrimental effect on amino acid balance. Some examples of small effects of genotype and sex on amino acid composition of pork were shown. [Copyright &y& Elsevier]

A cyclical changeover design experiment (3-wk periods; 12-wk total) was conducted to evaluate whether improving the balance of absorbable AA would allow the feeding of less crude protein (CP) without compromising production, thereby reducing the potential environmental pollution from dairy farms. Sixteen multiparous Holstein cows were assigned to 1 of 8 dietary treatments as total mixed rations (TMR) containing [dry matter (DM) basis] 45% corn silage, 5% coarsely chopped wheat straw, and 50% concentrate mixture. The 8 treatments were formulated to differ in dietary CP (14 and 16%; DM basis) and in the balance of absorbable AA achieved by changing the main protein source (MPS) of the concentrate mixtures [replacing soybean meal (SBM) with corn byproducts (CBP), dried corn distillers grains (DDG), and some corn gluten meal], and by adding a mixture of rumen-protected Lys and Met (RPLM). Feeding lactating dairy cows corn silage-based diets with 16% CP promoted significantly higher DM intakes and milk yields, and lower feed N-use efficiency than feeding diets with 14% CP. Replacing SBM with CBP significantly increased milk yields and decreased milk fat and protein concentrations, but had no effect on the efficiency of conversion of feed N into milk N. With 16% CP diets, the addition of RPLM decreased feed N use efficiency. A significant effect was observed for the MPS x RPLM interaction on milk protein concentrations. Plasma Lys concentration was lower with diets based on CBP, and plasma Met increased with RPLM. We did not find clear benefits of RPLM in facilitating a reduction of dietary protein without loss of production. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Oxidation of plasma cysteine/cystine (Cys/CySS) redox potential (EhCySS) has been associated with risk factors for cardiovascular disease in humans. Cys and CySS are derived from dietary sulfur amino acids (SAA), but the specific effects of SAA depletion and repletion on Cys/CySS redox indices are unknown. The present study examined the effect of dietary SAA intake level on free Cys, free CySS, and EhCySS in human plasma under fasting conditions. Methods: Healthy individuals aged 18–36 y (n = 13) were equilibrated to foods providing the RDA for SAA and then fed chemically defined diets without SAA (0 mg·kg–1·d–1; n = 13) followed by SAA at levels approximating the mean (56 mg·kg–1·d–1; n = 8) or 99th percentile (117 mg·kg–1·d–1; n = 5) intake levels of Americans. Fasting plasma samples were collected daily during 4-d study periods and analyzed for free Cys, free CySS, and the EhCySS. Results: The SAA-free diet significantly (P < 0.05) decreased plasma-free Cys concentrations and oxidized EhCySS values after 4 d of SAA depletion. With SAA repletion at 56 mg·kg–1·d–1, plasma-free Cys increased significantly and values for EhCySS became more reduced. Administration of a diet providing a higher dose of SAA (117 mg·kg–1·d–1) resulted in a significantly higher level of free Cys and a more reduced EhCySS. Conclusions: These results show that free Cys and Cys/CySS redox potential (EhCySS) in fasting plasma are affected by dietary SAA intake level in humans. Significant changes occur slowly over 4 d with insufficient SAA intake, but rapidly (after 1 d) with repletion. [Copyright &y& Elsevier]

: ObjectivesWe wanted to establish optimum protein and glucose intakes during total parenteral nutrition by using a constant caloric but changing protein intake in critically ill, ventilated, anuric patients on continuous renal replacement therapy and measuring amino acid and glucose losses across the hemofilter.: MethodsEleven consecutive, critically ill patients (eight male, age, 43.5 ± 21.8 y; Acute Physiology and Chronic Health Evaluation II score, 20.5 ± 7.0; Acute Physiology and Chronic Health Evaluation risk of death: 36.5% ± 23.0 and 6 ± 1 impaired organ systems) entered this study. Patients were fed by continuous infusion of a total parenteral mixture consisting of Synthamin (a mixture of essential and non-essential amino acids), 50% dextrose, and intralipid (long-chain triglycerides) to meet caloric requirements as predicted by Schofield''s equation corrected by stress factors. The amount of protein infused was varied (1 to 2.5 g · kg−1 · d−1) by increments of 0.25 g · kg−1 · d−1. Patients were stabilized on each feeding regimen for at least 24 h before paired samples of blood and dialysate were taken for amino acid and glucose measurements. Continuous renal replacement therapy was performed by using a blood pump with a blood flow of 100 to 175 mL/min. Dialysate was pumped in and out counter-currently to the blood flow at 2 L/h. A biocompatible polyacrylonitrile hemofilter was used in all cases.: ResultsWith protein intakes below 2.5 g · kg−1 · d−1, blood levels of 14% to 57% of the measured amino acids were below the lower limits of the normal range. At 2.5 g · kg−1 · d−1, all measured amino acids were within the normal range. Amino acid balance became more positive as protein input increased (P = 0.0001). Glucose and amino acid losses were dependent on blood concentration. Overall, 17% (range, 13% to 24%) of infused amino acids and 4% of infused glucose were lost in the dialysate.: ConclusionsThis study of critically ill, ventilated, anuric patients on continuous renal replacement therapy suggested that increases in protein and glucose are required to account for the increased losses across the hemofilter. A protein intake of 2.5 g · kg−1 · d−1 appeared to optimize nitrogen balance and correct amino acid deficiencies. [Copyright &y& Elsevier]

Background:We showed previously by the 24-h direct amino acid balance (DAAB) method that the leucine requirement of well-nourished Western and South Asian subjects is ≈40 mg · kg -1 · d -1. Objective: It is not known whether this estimated leucine requirement is applicable in chronic undernutrition; therefore, we assessed the leucine requirement in Indian men with chronic, but stable, undernutrition. Design: We studied 26 chronically undernourished men during 2 randomly assigned 7-d diet periods consisting of an L-amino acid diet (n = 20) and supplying either 14 and 30 (n = 10) or 22 and 40 (n = 10) mg leucine · kg -1 · d -1 or consisting of the subjects' habitual cereal-and-lentil-based diets (n = 6). The 24-h DAAB was estimated on day 6 by using a [13C]leucine tracer infusion. The splanchnic uptake of leucine was determined at an intake of 40 mg · kg -1 · d -1 by administering [2H3]leucine orally. Results: By using mixed-models linear regression of leucine balance against leucine intake, we estimated a zero leucine balance at a leucine intake of 39.6 mg · kg -1 · d -1. The splanchnic first-pass uptake of [2H3]leucine was 22.7% and 11.5% of the intake in the fasted and fed phases, respectively. The subjects were in neutral leucine balance with their habitual cereal-and-lentil-based diets. Conclusion: On the basis of the 24-h DAAB approach, a mean leucine requirement of 40 mg · kg -1 · d -1 is proposed for healthy and for chronically undernourished Indian adults. [ABSTRACT FROM AUTHOR]

Background: Because we question the validity of the 1985 FAO/ WHO/UNU upper requirement for threonine of 7 mg · kg-1· d-1, we proposed a tentative mean requirement of 15 mg · kg-1· d-1. Objective: Our goal was to assess threonine adequacy at 3 test intakes and the consequences of a 6-d compared with a 13-d dietary adaptation phase. Design: We used a 24-h indicator amino acid balance technique ([1-13C]leucine as indicator) to assess the threonine requirement. Fifteen healthy adults were randomly assigned to receive 7, 15, or 46 mg threonine · kg-1· d-1 and were studied after 6 and 13 d of adaptation to the experimental diets. Diets were based on an L-amino acid mixture in which the threonine content was varied. At 1700 on days 6 and 13, a 24-h intravenous [13C]leucine tracer infusion protocol was begun to assess leucine oxidation and daily leucine balances. Results: There was no detectable effect of duration of dietary adaptation in leucine oxidation or balance, but the 24-h leucine oxidation and balances differed significantly between the 7-mg intake and each of the 2 higher intakes (P < 0.05). The latter were not significantly different. The 24-h leucine oxidation rate decreased across threonine intakes (P < 0.01 for main effect of diet, independent of infusion day). Leucine oxidation was highly correlated (r = 0.80) between the 2 dietary adaptation phases across all test intakes. Conclusion: The 1985 FAO/WHO/UNU threonine recommendation is inadequate, and 15 mg · kg-1· d-1 is sufficient to achieve mean indicator (leucine) amino acid balance. [ABSTRACT FROM AUTHOR]

Changes in protein and amino acid balance after energy-restricted feeding have scarcely been studied, although it has been suggested that protein utilization may depend on the macronutrient composition of the restricted diet. The aim of this study is to investigate the influence of dietary fat quality and content, during an energy-restricted regime, on body composition and protein metabolism. Therefore, diet-induced overweight rats were divided into three dietary groups: one group was fed on a control diet ad libitum (control) and the other two groups were fed energy-restricted diets (about 60% of control group), which provided a standard amount (20%) of fat (SFR), based on olive oil, or a high amount (60%) of saturated fat (HFR), based on coconut oil. Measurements of body weight, body composition, serum biochemical parameters and the assessment of the hepatic and muscular protein response were performed. Similar results were found comparing weight losses and serum parameters in both deprived groups, although the high-fat-restricted rats (HFR group) showed a greater reduction in the subcutaneous fat depot and of total body fat. After both energy-restricted treatments, the serum amino acid concentration was reduced while the urinary amino acid excretion increased. Muscle and liver protein metabolism was affected by energy restriction, which produced a decrease in protein synthesis capacity (RNA content) in both tissues and a higher muscle proteolysis (catepsin activity), more marked in the SFR group, while no changes were found in liver protein breakdown. Hepatic glycogen and glycogenic amino acid were also altered, reaching significant differences in the HFR group. Thus, dietary macronutrient composition during energy restriction seems to be involved in the metabolic adaptative response.Copyright © 2002 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background: The 1985 FAO/WHO/UNU requirement for leucine is too low according to tracer-derived estimates of leucine oxidation and balance in adults from developed regions. Objective: The leucine requirement in populations in developing countries was assessed with use of the 24-h tracer balance method and on the basis of nitrogen balances. Design: Twenty healthy Indian men were studied during their consumption for 6 d of 2 L-amino acid diets that supplied either 14 and 30 (n = 10) or 22 and 40 (n = 10) mg leucine⋅kg-1⋅d-1 in random order. At 1800 on day 7, a 24-h constant intravenous [13C]leucine tracer-infusion protocol was conducted to determine leucine oxidation and daily leucine balance. During the intake of 40 mg leucine/d, [²H3]leucine was given orally to assess the splanchnic uptake of leucine. Results: Mean 24-h leucine oxidation rates were 29.8, 30.6, 33.6, and 39.3 mg⋅kg-1⋅d-1 at leucine intakes of 14, 22, 30, and 40 mg⋅kg-1⋅d-1, respectively; daily leucine balances were -16.5, -9.0, -3.3, and 0.5 mg⋅kg-1⋅d-1, respectively. Mixed-models linear regression of balance against leucine intake resulted in a zero balance at a leucine intake of 37.3 mg⋅kg-1⋅d-1. Nitrogen balances were -12.7, -17.9, -3.9, and 1.0 mg⋅kg-1⋅d-1 at leucine intakes of 14, 22, 30, and 40 mg⋅kg-1⋅d-1. Regression of nitrogen balance against intake resulted in a zero balance at a leucine intake of 37.6 mg⋅kg-1⋅d-1. The first-pass splanchnic uptake of leucine was 45.7% and 33.9% in the fasted and fed periods, respectively. Conclusion: A tentative mean leucine requirement of 40 mg⋅kg-1⋅d-1 is proposed for healthy Indian adults, as it is for Western subjects. [ABSTRACT FROM AUTHOR]

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This is a review of previously published data from experiments designed to measure the chicks' requirement for an essential amino acid in diets containing surplus protein (generally in the range 220–300 g crude protein (CP)/kg diet). The evidence shows that, within this range, the requirement for a first limiting amino acid increases nearly in direct proportion to the CP content of the diet. To explain this, the following possibilities are considered: (1) that energy supply was limiting the response to a critical amino acid, (2) that the experiments were conducted in environments which limited heat disposal by the chicks, (3) that results from the trials have been misinterpreted because growth rate rather than protein deposition was used as a response measure, (4) that the availability of amino acids in the diets was lower than had been assumed, (5) that nutrients other than the amino acid under study were limiting performance, and (6) that there was an imbalance of amino acids in the diet. It is concluded that only the last explanation fits the facts. The imbalances reported have led to a decline in the efficiency of the utilisation of the first limiting amino acid in some instances. The depressed growth observed with a high-protein diet limiting in one essential amino acid could not be attributed to lowered feed intake in most cases. The imbalance is, in these respects, different from classical imbalances which result from loading the diet with a mixture of essential amino acids. From the evidence reviewed, some doubt is cast on the validity of the dilution method for estimating amino acid requirements; nevertheless it its concluded that the dilution method remains the most trustworthy procedure for making estimates to be used in practical diet formulation. It is recommended that, in future, programmes for diet formulation should be modified to prevent surplus protein being permitted in the solution, unless a proportional adjustment is made to the minima prescribed for amino acids likely to be present in limiting proportions. [ABSTRACT FROM PUBLISHER]

Based on the nitrogen balance (NB) data and the efficiency of amino acid utilization, optimum supplements of limiting amino acids (AA) to triticale were calculated and their effect on true N digestibility (TD), biological value of protein (BV) and net protein utilization (NPU) of a triticale-based diet was evaluated. To determine if AA balance must be considered in the calculation of the optimum supplements, the effect of a 20% or 40% excess of essential AA in lysine-, methionine-, threonine- or tryptophan-deficient diets was also studied. The AA excess had no significant effect on NB in diets deficient in lysine, methionine or threonine. However, NB in rats fed on the tryptophan-deficient diet increased as the AA excess increased. BV of the diet containing the optimized supplements of lysine, threonine, methionine and valine was comparable to that of lactalbumin or to the diet supplemented with all essential AA. The deletion of valine from the optimized supplement caused an insignificant decrease in BV. Due to the lower TD, NPU of diets containing the optimized AA supplements was lower than that of the diet containing all essential AA or of the lactalbumin-based diet. [ABSTRACT FROM AUTHOR]

The changes in hind leg tissue (muscle and skin) amono acid pool size and arteriovenous balance were measured in rats subjected to 0-90 min of cold exposure (4°C). Tissue free amino acid pools presented a different composition pattern from protein amino acids. Muscle rapidly reacted to cold exposure by releasing small amounts of some amino acids (alanine, aspartate), with only small changes in pool size during the first 30 min. Amino acid oxidation was very limited during the whole period of cold exposure, since at all times tested there was either nil ammonia efflux or net absorption of ammonia and glutamine; i.e. the muscle was in positive nitrogen balance throughout the period studied. Thus most of the amino acid nitrogen taken up from the blood and not found in the free amino pools must have been incorporated into protein, since it was not oxidized, as shown by the glutamine and ammonia blance. The data on amino acid incorporation into proteins indicate that hind leg protein turnover is rapidly and widely modulated from a low initial setting upon cold exposure to a higher protein synthesis rate immediately afterwards, suggesting that protein turnover may have an important role in short-term events in cold-exposed muscle, in addition to its influence in long-term adaptation. [ABSTRACT FROM AUTHOR]

The amino acid composition of the diet ingested by reference and cafeteria diet-fed lean and obese Zucker rats has been analyzed from day 30 to 60 after birth. Their body protein amino acid composition was measured, as well as the urinary and faecal losses incurred during the period studied. The protein actually selected by the rats fed the cafeteria diet had essentially the same amino acid composition as the reference diet. The mean protein amino acid composition of the rat showed only small changes with breed, age or diet. Cafeteria-fed rats had a higher dietary protein digestion/absorption efficiency than reference diet-fed rats. Obese rats wasted a high proportion of dietary amino acids when given the reference diet, but not on the cafeteria diet. In all cases, the amino acids lost as such in the urine were a minimal portion of available amino acids. In addition to breed, the rates of protein accretion are deeply influenced by diet, but even more by the age - or size - of the animals: cafeteria-fed rats grew faster, to higher body protein settings, but later protein accrual decreased considerably; this is probably due to a limitation in the 'blueprint for growth' which restricts net protein deposition when a certain body size is attained. Obese rats, however, kept accuring protein with high rates throughout. Diet composition - and not protein availability or quality-induced deep changes in amino acid metabolism. Since the differences in the absolute levels of dietary protein or carbohydrate energy ingested by rats fed the reference or cafeteria diets were small, it can be assumed that high (lipid) energy elicits the changes observed in amino acid metabolism by the cafeteria diet. The effects induced in the fate of the nitrogen ingested were more related to the fractional protein energy proportion than to its absolute values. Cafeteria-fed rats tended to absorb more amino acids and preserve them more efficiently; these effects were shown even under conditions of genetic obesity. There were deep differences in handling of dietary amino acids by dietary or genetically obese rats. The former manage to extract and accrue larger proportions of their dietary amino acids than the latter. The effects of both 'models' of amino acid management were largely additive, suggesting that the mechanisms underlying the development of obesity did not run in parallel to those affecting the control of amino acid utilization. Obesity may be developed in both cases despite a completely different strategy of amino acid assimilation, accrual and utilization. (Mol Cell Biochem 121: 45-58, 1993) [ABSTRACT FROM AUTHOR]

The synergistic regulation effect of coordinated application of nitrogen (N) and sulfur (S) on the protein concentration and amino acid balance in maize grains was investigated. The results showed that the coordinated application of N and S significantly increased the protein concentration of maize grains, and there were significant N × S interactions. In addition, the coordinated application of N and S also increased concentration of essential amino acid in maize grains, and N × S interactions reached a significant level. Simultaneously, the ratio of total essential amino acid to total non-essential amino acid in maize grains was increased, which promoted the balance of amino acid in grain protein. Notably, lysine and tryptophan that were usually most deficient in maize grains were significantly increased due to coordinated application of N and S, which was critical for improving nutritional quality of maize. Overall, synergistic application of N and S simultaneously improved protein concentration and amino acid balance in maize grains, thereby significantly improving nutritional quality of maize. [Display omitted] • The nutritional quality of maize grains was evaluated. • Coordination application of N and S increased protein concentration of maize grains. • Content of essential amino acid increased by synergistic application of N and S. • Coordination application of N and S promoted the balance of amino acid in protein. [ABSTRACT FROM AUTHOR]

Marketing strategies and feeding costs are key factors affecting the sustainability of intensive aquaculture systems. The present 44-day feeding trial aimed to model the optimum levels of balanced digestible protein (BDP) for adult pacu (Piaractus mesopotamicus) and develop an economic optimization procedure for the final yield. The experiment was conducted in a freshwater recirculation aquaculture system (RAS). A randomized block design with six treatments and three replicates was used. A total of 180 pacu adults with initial body weight of 1158.50 ± 21.59 g (± standard deviation) were distributed (10 fish per tank) among 18 concrete-tanks of 2000 L. Six consecutive isoenergetic experimental diets containing 163, 201, 238, 272, 315 and 348 g BDP kg−1 (dry matter basis – DM basis) were prepared through the diet dilution procedure. The triplicate groups of fish were hand-fed three times a day at 09:00, 12:00 and 17:00 h until apparent satiation. At the end of the trial, the productive and economic responses were evaluated through appropriate mathematical models and statistical analyses. The optimum levels of BDP were modeled as 232 and 245 g kg−1 (DM basis) by the quadratic model based on maximum final body weight (FBW) and body weight gain (BWG) of adult pacu, respectively. Using an individual based economic model, the economically optimized levels of BDP were modeled as 215, 217 and 222 g kg−1 (DM basis) for obtaining maximum profitability from the fish that are marketed in the form of whole-body, eviscerated and sliced adult pacu, respectively. The optimum levels of BDP modeled for maximum profitability were found considerably lower than those modeled for maximum FBW and BWG. The hypothesized scenarios confirmed that profitability and economically optimized levels of dietary protein were greatly affected by the fluctuations in feed costs and marketing strategy of the final yield. • The biological levels of balanced digestible protein resulted in maximum productive performance of adult pacu • The economic levels of balanced digestible protein yielded maximum profitability with better productive performance • The economic returns of the final yield were greatly subjected to the changes in marketing strategies • The development of economically optimized aquafeeds may play a substantial role in sustainable aquaculture [ABSTRACT FROM AUTHOR]

Bacterial cells utilize toxin-antitoxin systems to inhibit self-reproduction, while maintaining viability, when faced with environmental challenges. The activation of the toxin is often coupled to the induction of cellular response pathways, such as the stringent response, in response to multiple stress conditions. Under these conditions, the cell enters a quiescent state referred to as dormancy or persistence. How toxin activation triggers persistence and induces a systemic stress response in the alphaproteobacteria remains unclear. Here, we report that in Caulobacter , a hipA2 -encoded bacterial toxin contributes to bacterial persistence by manipulating intracellular amino acid balance. HipA2 is a serine/threonine kinase that deactivates tryptophanyl-tRNA synthetase by phosphorylation, leading to stalled protein synthesis and the accumulation of free tryptophan. An increased level of tryptophan allosterically activates the adenylyltransferase activity of GlnE that, in turn, deactivates glutamine synthetase GlnA by adenylylation. The inactivation of GlnA promotes the deprivation of glutamine in the cell, which triggers a stringent response. By screening 69 stress conditions, we find that HipBA2 responds to multiple stress signals through the proteolysis of HipB2 antitoxin by the Lon protease and the release of active HipA2 kinase, revealing a molecular mechanism that allows disparate stress conditions to be sensed and funneled into a single response pathway. IMPORTANCE To overcome various environmental challenges, bacterial cells can enter a physiologically quiescent state, known as dormancy or persistence, which balances growth and viability. In this study, we report a new mechanism by which a toxin-antitoxin system responds to harsh environmental conditions or nutrient deprivation by orchestrating a dormant state while preserving viability. The hipA2 -encoded kinase functions as a toxin in Caulobacter , inducing bacterial persistence by disturbing the intracellular tryptophan-glutamine balance. A nitrogen regulatory circuit can be regulated by the intracellular level of tryptophan, which mimics the allosteric role of glutamine in this feedback loop. The HipBA2 module senses different types of stress conditions by increasing the intracellular level of tryptophan, which in turn breaks the tryptophan-glutamine balance and induces glutamine deprivation. Our results reveal a molecular mechanism that allows disparate environmental challenges to converge on a common pathway that results in a dormant state., (Copyright © 2021 Zhou et al.)

As a major component of biologically active compounds in the body, proteins contribute to the synthesis of body tissues for the renewal and growth of the body. The high level of dietary protein and the imbalance of amino acid (AA) composition in mammals result in metabolic disorders, inefficient utilization of protein resources and increased nitrogen excretion. Fortunately, nutritional interventions can be an effective way of attenuating the nitrogen excretion and increasing protein utilization, which include, but are not limited to, formulating the AA balance and protein-restricted diet supplementing with essential AAs, and adding probiotics in the diet. This review highlights recent advances in the turnover of dietary proteins and mammal's metabolism for health, in order to improve protein bioavailability through nutritional approach., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

The article presents an abstract of the research paper "Comparison of digestible lysine needs in the starter period when fed diets formulated to ideal ratios or added alone," by F.G.P. Costa and colleagues.

There is growing recognition that composition and metabolic activity of the gut microbiota can be modulated by the dietary proteins which in turn impact health. The amino acid composition and digestibility of proteins, which are influenced by its source and amount of intake, play a pivotal role in determining the microbiota. Reciprocally, it appears that the gut microbiota is also able to affect protein metabolism which gives rise to the view that function between the microbiota and protein can proceed in both directions. In response to the alterations in dietary protein components, there are significant changes in the microbial metabolites including short chain fatty acids (SCFAs), ammonia, amines, gases such as hydrogen, sulfide and methane which are cytotoxins, genotoxins and carcinogens associated with development of colon cancer and inflammatory bowel diseases. A suitable ratio between protein and carbohydrate or even a low protein diet is recommended based on the evidence that excessive protein intake adversely affects health. Supplying high and undigested proteins will encourage pathogens and protein-fermenting bacteria to increase the risk of diseases. These changes of microbiota can affect the gut barrier and the immune system by regulating gene expression in relevant signaling pathways and by regulating the secretion of metabolites. The objective of this review is to assess the impact of dietary proteins on microbiota composition and activity in the gastrointestinal tract. Attention should be given to the dietary strategies with judicious selection of source and supplementation of dietary protein to benefit gut health., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.)