Availability Of Individual Amino Acids Research Articles

Recent advances in amino acid sensing and new challenges for protein nutrition in aquaculture

From the conventional knowledge of protein nutrition to the molecular nutrition of amino acids, our understanding of protein/amino acid nutrition is rapidly increasing. Amino acids control cell growth and metabolism through two amino acid-sensing pathways, i.e. target of rapamycin complex 1 (TORC1) and the general control nonderepressible 2 (GCN2) signaling pathway. In the amino acid-abundant status, TORC1 dominates intracellular signaling and increases protein synthesis and cell growth. In contrast, amino acid deprivation actives GCN2 resulting in repression of general protein synthesis but facilitates the amino acid transport and synthesis process. By integrating and coordinating nutrition and hormone signaling, TORC1 and GCN2 control the switch of the catabolism and anabolism phase in most eukaryotes. Now, we appreciate that the availability of individual amino acids is sensed by intracellular sensors. These cutting-edge findings expand our knowledge of amino acid nutrition. Although the TORC1 and GCN2 were discovered decades ago, the study of molecular amino acid nutrition in aquaculture animals is still at its infancy. The aquaculture industry is highly dependent on the supply of fishmeal, which is the major protein source in aquacultural animal diets. Some concerted efforts were conducted to substitute for fishmeal due to limited supply of it. However, the concomitant issues including the unbalanced amino acid profile of alternative protein sources limited the utilization of those proteins. Continued study of the molecular nutrition of amino acid in aquaculture animals may be expected in the immediate future to expand our knowledge on the utilization of alternative protein sources.

Amino acid availability of selected plant products and fish meal for American alligator (Alligator mississippiensis)

Digestibility trials were conducted to determine the amino acid availability of selected ingredients (corn grain, soybean meal, soy protein concentrate, wheat gluten, and menhaden fish meal) fed to American alligator at inclusion levels of 30% or 45% of the diet. Apparent crude protein digestibility of soybean meal and soy protein concentrate was significantly reduced at the higher dietary inclusion level, while crude protein digestibility of wheat gluten was unaffected (P>0.05). Energy digestibility of soybean meal also was significantly reduced at the 45% inclusion level, but energy digestibility of soy protein concentrate and energy digestibility of wheat gluten did not change (P>0.05) at either inclusion level. Crude protein digestibility of yellow corn grain was not affected (P>0.05) by corn inclusion level, but energy digestibility of corn was reduced (P<0.05) at 45% corn inclusion. Neither crude protein digestibility nor energy digestibility of menhaden fish meal were affected by dietary inclusion level in two size classes of alligator tested. One or more statistically significant differences in availability of individual amino acids were observed for some ingredients fed at the two dietary inclusion levels. In the majority of cases where a statistically significant difference occurred, the availability of the affected amino acid was significantly lower at 45% ingredient inclusion than at 30% inclusion. Among presumed dietary essential amino acids, this was the case for arginine, histidine and phenylalanine in corn and menhaden fish meal; lysine in soy protein concentrate, wheat gluten, and menhaden fish meal; and isoleucine, leucine, and valine in menhaden fish meal fed to larger alligators. In corn and menhaden fish meal fed to smaller alligators, apparent availability of methionine was higher (P<0.05) at the 45% ingredient inclusion level than at 30% inclusion. No differences (P>0.05) were observed in the availability of any amino acid in soybean meal fed at 30% or 45% of the diet. Results indicated that American alligator efficiently digested crude protein and energy in an assortment of plant products of varied chemical composition which could be used as alternatives to animal protein in compounded diets. Availability of dietary essential amino acids also was usually high (often greater than 90%) when these ingredients were provided at levels of 30–45% of the diet.

Amino Acids for the Neonate: Search for the Ideal Dietary Composition

Amino acids play crucial roles as precursors for proteins and neurotransmitters, as transport molecules, and in cell signaling. In this review, we describe the unique functions of the individual amino acids and conclude that the amino acid requirements of parenterally fed neonates are inadequately defined. Parenterally fed neonates are at risk of amino acid deficiency or toxicity because the intestines serve as an important site of metabolism, regulating systemic availability of individual amino acids.

Alternative protein sources in diets for Japanese flounder Paralichthys olivaceus (Temminck and Schlegel): II. Effects on nutrient digestibility and digestive enzyme activity

An 8-week feeding trial was conducted to compare the effects of dietary protein sources on nutrient digestibility and digestive enzyme activity. Four experimental diets were formulated to contain one of the following as the sole protein source: fish meal (FM), fish protein concentrate (FPC), soy protein concentrate (SPC) and soy protein isolate (SPI). Each diet was randomly assigned to triplicate aquaria stocked with 25 Japanese flounder (Paralichthys olivaceus) each. The dry matter, crude protein and energy digestibility and individual amino acid availability of the SPC-based diet were significantly lower than those of the other diets. The crude lipid digestibility of soy protein-based diets was significantly lower than that of the FM-based diet. The pepsin/protease activity was significantly higher in fish fed fish protein-based diets compared with fish fed soy protein-based diets. The lipase activity in fish fed the SPI-based diet was the highest among the dietary treatments. These results indicate that P. olivaceus can effectively digest the protein from FPC and SPI (but not SPC) as well as FM. The low protein digestibility and amino acid availability of the SPC-based diet may be related to the non-protein compounds present in SPC, whereas the low-lipid digestibility of soy protein-based diets may contribute to the undigested soy protein fractions and/or the alcohol-soluble components.

Amino acid availability regulates S6K1 and protein synthesis in avian insulin-insensitive QM7 myoblasts

The regulation of S6K1 by nutritional status and insulin has been recently reported in vivo in chicken muscle despite the relative insulin resistance of this tissue as estimated by phosphatidylinositol 3-kinase (PI3-kinase) activity. The present work aimed to study the impact of amino acids on S6K1 activity in quail muscle (QM7) myoblasts. Firstly, we characterized S6K1 in QM7 cells and demonstrated the absence of insulin receptors in these cells. Secondly, we showed that amino acids in the absence of insulin induced S6K1 phosphorylation on Thr389 and concomitantly increased its enzymatic activity. Amino acid-induced S6K1 activation was inhibited by LY294002 (PI3-kinase inhibitor) and rapamycin (inhibitor of the mammalian target of rapamycin, mTOR), suggesting the involvement of an avian homolog of mTOR. The availability of individual amino acids (methionine or leucine) regulated S6K1 phosphorylation on Thr389 and QM7 protein synthesis. In conclusion, amino acids regulate S6K1 phosphorylation and activity in QM7 cells through the mTOR/PI3-kinase pathway in an insulin-independent manner.

Apparent digestibility of crude protein and apparent availability of individual amino acids in tilapia ( Oreochromis niloticus ) fed phytase pretreated soybean meal diets

Soybeans contain phytates, the anionic forms of 1,2,3,5/4,6-hexakis (dihydrogen phosphate) myoinositol, with the potential to reduce amino acid (AA) availability. Tilapia lack the intestinal enzyme phytase to hydrolyze phytates. Oreochromis niloticus (approximately 68 g) were fed diets containing either phytase pretreated or untreated soybean meal (SBM) incorporated at 0, 25, 50, 75, or 100% of the crude protein (CP) in a 33% CP diet to determine whether phytates reduce CP digestibility and AA availability. There were no differences in apparent CP digestibility. Dietary and available methionine (Met), and available lysine (Lys), decreased with increasing incorporation of phytase pretreated SBM. Reduced availability of Met and Lys from the phytase pretreated diets was likely due to removal of phytates. Phytates may reduce the effect of other antinutritional factors, protect amino acids from degradation, or decrease leaching of water soluble components.

Replacement of fish meal in diets for Australian silver perch, Bidyanus bidyanus: I. Digestibility of alternative ingredients

Apparent digestibility coefficients (ADCs) for dry matter, nitrogen, energy and individual amino acids for 29 commonly used feed ingredients were determined for silver perch, a native Australian freshwater species currently being cultured in Australia, Taiwan and China. ADCs were determined using faeces collected following settlement. Results from 11 experiments are reported. Each experiment included a reference diet and test diets, which were composed of 69.3% reference diet, 29.7% test ingredient and 1% chromic oxide (inert indicator). Ingredients tested included Australian, Danish and Peruvian fish meals, blood meal, meat and bone meals from beef and lamb, poultry meal, feather meal, soybean and canola meals (both expeller and solvent extracted for each), full fat soybeans, peanut meal, cottonseed meal, linola, two species of lupins, field peas, faba beans, chick peas, vetch, cow peas, wheat gluten, corn gluten meal, two cultivars of wheat, millrun and sorghum. ADCs for dry matter, energy and nitrogen were highest for fish meal, although several other ingredients, including some animal meals and gluten from wheat and corn, had similar ADCs for dry matter and energy. Digestible protein from these ingredients was in the range 52–86% compared with 63–69% for fish meals. Silver perch were capable of digesting protein very effectively in almost all ingredients tested. Amino acid availability reflected nitrogen digestibility except for Peruvian fish meal and the two meat and bone meals, for which the availability of some amino acids was lower, possibly indicating protein damage during processing. Oilseeds and legumes also tended to have lower ADCs for some amino acids (e.g., sulphur amino acids) than for other amino acids. Differences in ADCs for nitrogen and individual amino acids indicate the need for individual amino acid availability data. The data provided a useful starting point for least-cost formulation of diets for silver perch.

A review of methods for assessing the protein value of grain fed to ruminants

The protein value of feed grains for ruminant rations is currently described in modern feeding systems in terms of total protein, potentially degradable protein, and potentially undegradable protein. Progress is being made towards full standardisation of methods to measure these components, although it is a goal yet to be achieved. Whereas in the future it is desirable that protein value be defined in terms of individual amino acid availability at the intestine, in the immediate term it can best be described by the rate and extent of degradability of protein in the rumen and the availability in the intestine of the rumen undegraded protein. Refining the methodology for measuring these characteristics is important, but it is equally important that the existing methods be validated using in vivo experimentation.

Digestibility, Apparent Amino Acid Availability and Waste Generation Potential of Soybean Flour-Poultry Meat Meal Blend Diets for the Sharp-Toothed Catfish, Clarias gariepinus, Fingerlings

ABSTRACT Nutrient digestibility and amino acid availability were assessed in sharp-toothed catfish, Clarias gariepinus, fingerlings fed diets containing soybean flour (SF): poultry meat meal (PMM) blends (25:75, 50:50, and 75:25) and 0.5 or 1.0% Cr2O3. There was agreement between the pattern of overall protein digestibility and average amino acid availability, despite the variability in individual amino acid availability. The best dry matter, lipid, and protein digestibility coefficients and amino acid availability values were obtained with diets containing 0.5%. Chromic oxide inclusion level appeared to affect nutrient availability. Increased marker level resulted in decreased nutrient digestibility coefficients. Similarly, these diets generated lower fecal crude protein than those with 1.0% 0203. However, the latter group recorded higher protein retention efficiency. Dry matter and lipid of diets containing more soybean flour seemed to be more digestible than those of poultry meat meal. A similar trend was observed for the apparent availability of the amino acids. This investigation has indicated that low level of marker was better in digestibility study. Utilization of more SF than PMM in the diets of this catfish was more beneficial and should be encouraged in the feed industries producing catfish diets.

Amino Acid Availability and Availability-Corrected Amino Acid Score of Red Kidney Beans (Phaseolus vulgaris L.)

Thermal effect on availability of individual amino acids (AIAA) of red kidney beans was evaluated. Sulfur amino acids (SAA), methionine and cystine (Met + Cys), are the limiting amino acids (AA) an...

Digestibility, apparent amino acid availability and waste generation potential of soybean flour: poultry meat meal blend based diets for tilapia, Oreochromis niloticus (L.), fingerlings

Nutrient digestibility and amino acid availability were assessed in tilapia, Oreochromis niloticus (L.), fingerlings fed diets containing soybean flour (SF): poultry meat meal (PMM) blends (25:75, 50:50 and 75:25), and 0.5 or 1.0% Cr2O3. Although there was variability in individual amino acid availability, average availability was in agreement with the pattern of overall protein digestibility. The best lipid, protein digestibility and amino acid availability values were obtained in the 75:25 SF:PMM blend and 0.5% Cr2O3 treatment, which corresponded to the lowest level of faecal crude protein while the best ash digestibility was observed with 25:75 SF:PMM blend and 1.0% Cr2O3. Chromic oxide inclusion level appeared to affect nutrient availability. Increased marker level might have resulted in decreased nutrient digestibility coefficients. Protein and lipid of diets containing more soybean flour seemed to be more digestible than those of poultry meat meal while the reverse was the case for ash.

Methods for Determining Amino Acid Availability of Feeds

ALTHOUGH protein values have been well established and amino acid values are rapidly being determined for feeds, there is limited information concerning biological availability of individual amino acids in grain and protein concentrates. Price et al. (1953) employed chick carcass and excreta analysis to evaluate dietary amino acids and proteins. It was shown that neither dietary level nor age of chick markedly affected the content of the various amino acids of the carcass. However, excreta from chicks fed high protein diets were higher in certain amino acids when compared to excreta from those fed low protein diets. De Muelenaere et al. (1967) determined lysine availability of cereal products by fecal and growth analysis. These workers concluded that growth analysis often yielded values which exceeded 100% and that method of evaluation may influence availability values.For the above reasons it appeared that a measurement of digestibility or the actual disappearance of…

Limiting Essential Amino Acids in Soybean Meal for Growing Chickens and the Effects of Heat Upon Availability of the Essential Amino Acids

THE seriously limiting essential amino acids in a feedstuff can generally be identified by comparing the feedstuff's chemically determined amino acid content with the amino acid pattern needed to produce rapid growth. It is sometimes difficult to identify marginally deficient amino acids by this method, however. The availability of individual amino acids is affected to different degrees by the processes used in producing a feedstuff; this also makes it more difficult to identify the limiting amino acids. For these reasons chick tests are being conducted at this station to determine which amino acids are most limiting in the protein of several commonly used poultry feedstuffs. Two previous papers have reported results of experiments conducted with peanut and cottonseed meals (Anderson and Warnick, 1965, 1966).In the experiments with peanut and cottonseed meals, the rations contained 18 percent protein from the feedstuff studied and a mixture of the amino acids thought .