Essential Amino Acid Requirements Research Articles

Determination of digestible lysine and estimation of essential amino acid requirements for bullfrogs

The traditional method to determine the nutritional requirements of animals is based on individual dose–response experiments that are time consuming and costly. One alternative to establish the dietary protein profile is the use of the ideal ratio between essential amino acids and digestible lysine to estimate essential amino acid requirements. The objective of this study was to determine the digestible lysine requirement of bullfrogs and to estimate essential amino acid requirements based on the ideal ratio. The experimental design was completely randomized and consisted of five treatments and three replicates. Six hundred froglets with an initial mean weight of 51.53±1.91g, identified through an implanted transponder, were used. The experimental diet (30.42% digestible protein) was supplemented with five levels of lysine HCl (0, 0.7, 1.4, 2.1, and 2.8%), so that the diets contained 1.38, 2.11, 2.85, 3.65 and 4.39% digestible lysine. The performance variables were feed intake, weight gain, feed conversion, specific growth rate, protein efficiency ratio, protein retention efficiency, and body protein and lysine deposition. The optimum level of digestible lysine was obtained at the intersection of the ascending line with the response plateau. Weight gain increased until reaching 222.7g at 2.23% digestible lysine in the diet. The best feed conversion (1.4g/g) and body protein (48.28g) and lysine (4.07g) deposition were observed at 2.29%, 2.33% and 2.39% digestible lysine, respectively. The digestible lysine requirement of bullfrogs is 2.71% of dry weight or 8.91% of dietary digestible protein, a level that provides the highest protein retention efficiency. The requirements of the other digestible amino acids estimated based on the concept of the ideal ratio of essential amino acids are (of dry weight): 2.16% arginine; 0.94% histidine; 1.34% isoleucine, 2.39% leucine; 0.79% methionine; 1.31% phenylalanine; 1.34% threonine; 0.23% tryptophan; 1.58% valine; 0.36% cystine, and 1.07% tyrosine. Statement of RelevanceThe estimate requirement of digestible essential amino acid using the concept of the ideal ratio permits the elaboration of diets with an appropriate amino acid, maximizing growth, protein utilization efficiency and carcass quality for bullfrogs.

Effect of l‐glutamic acid supplementation on performance and nitrogen balance of broilers fed low protein diets

The aim of this study was to evaluate the effect of protein reduction and supplementation of l-glutamic acid in male broiler diets. A total of 648 chicks of the Cobb 500 strain were distributed in a completely randomized design with six treatments and six replications with eighteen birds per experimental unit. The study comprised pre-starter (1-7days), starter (8-21days), growth (22-35days) and final (36-45days) phases. The first treatment consisted of a control diet formulated according to the requirements of essential amino acids for each rearing phase. The second and third treatments had crude protein (CP) reduced by 1.8 and 3.6 percentage points (pp) in relation to the control diet respectively. In the fourth treatment, l-glutamic acid was added to provide the same glutamate level as the control diet, and in the last two treatments, the broilers were supplemented with 1 and 2pp of glutamate above that of the control diet respectively. The reduction in CP decreased the performance of broilers and the supplementation of l-glutamic acid did not influence performance when supplied in the diets with excess of glutamate. The lowest excreted nitrogen values were observed in the control diet, and treatments 2 and 3, respectively, in comparison with treatments with the use of l-glutamic acid (5 and 6). Retention efficiency of nitrogen was better in the control diet and in the treatment with a reduction of 1.8pp of CP. It was verified that the serum uric acid level decreased with the CP reduction. A reduction in CP levels of up to 21.3%, 18.8%, 18.32% and 17.57% is recommended in phases from 1 to 7, 8 to 21, 22 to 35 and at 36 to 42days, respectively, with a level of glutamate at 5.32%, 4.73%, 4.57%, 4.38%, also in these phases.

Nutritional Evaluation of Four Commercially Available Pollen Patties in Korea

Pollen patty is one of the requirements for commercial beekeeping especially in early spring when overwintered honey bee colony begin production of brood. The quality and quantity of pollen patty substituting the natural sources of protein and carbohydrate could determine the spring colony production, but limited information is available in nutritional contents of commercial pollen patties in Korea. We analysed nutrient contents of four commercially available pollen patties and compared with recommended requirement of essential amino acids for honey bee. The results revealed that protein content of different pollen patties ranged 18.9 to 22.4%.The recovery of the protein in terms of amino acids was found more than 90%. The analytical data showed that phenylalanine was limiting while sufficient tyrosine was present. High tyrosine levels could decrease the need for dietary phenylalanine. Arginine was found another limiting amino acid and histidine was present in marginal level. Fat content of four patties ranged 0.7 to 1.3%. Overall, this study results showed that protein enforced pollen patty could serve as natural pollen alternative in early spring.

Effective translation of current dietary guidance: understanding and communicating the concepts of minimal and optimal levels of dietary protein

Dietitians and health care providers have critical roles in the translation of the dietary guidance to practice. The protein content of diets for adults can be based on the Recommended Dietary Allowance (RDA) of 0.80 g/kg per day. Alternatively, the most recent Dietary Reference Intakes (DRIs) for macronutrients reflect expanded guidance for assessing protein needs and consider the relative relation of absolute amounts of protein, carbohydrate, and fat to total energy intake in the context of chronic disease prevention. The Acceptable Macronutrient Distribution Range (AMDR) reflects the interrelation between the macronutrients and affords dietitians and clinicians additional flexibility in diet planning. Accounting for the caloric value of RDAs for carbohydrate and fat, "flexible calories" emerge as an opportunity to create varied eating plans that provide for protein intakes in excess of the RDA but within the AMDR. Protein Summit 2.0 highlighted the growing body of scientific evidence documenting the benefits of higher protein intakes at amounts approximating twice the RDA, which include promotion of healthy body weight and preservation of lean body mass and functional ability with age. The essential amino acid (EAA) density of a food also emerged as a novel concept analogous to "nutrient density," which can enable the practitioner to calculate the caloric cost associated with a specific protein source to attain the daily requirement of EAAs to accomplish various health outcomes because these indispensable nutrients have a significant role in protein utilization and metabolic regulation. Tailoring recommendations unique to an individual's varying goals and needs remains a challenge. However, flexibility within the application of DRIs to include consideration of the AMDR provides a sound framework to guide practitioners in effective translation of current dietary guidance with a specific regard for the documented benefits of higher protein intakes.

Concept and application of ideal protein for pigs.

Knowledge about the amino acid requirements and the response of pigs to the amino acid supply is essential in feed formulation. A deficient AA supply results in a reduction in performance while an oversupply is costly and leads to excessive nitrogen excretion with a potentially negative environmental impact. Amino acid requirements are determined to a large extent by the protein deposition in the body and, for lactating sows, by the protein exported in the milk. The concept of ideal protein was developed more than 50 years ago and refers to a protein with an amino acid profile that exactly meets the animal’s requirement so that all amino acids are equally limiting for performance. Because Lys typically is the first-limiting amino acid, the ideal amino acid profile is often expressed relative to Lys. Although the ideal protein profile is often assumed to be constant for a given production stage, (small) changes in the ideal protein profile can occur within a production stage. This can be caused by changes in the relative contribution of the different components of amino acid requirements during the productive life on the animal (e.g. changes in the relative contribution of growth and maintenance). Amino acids requirements can be determined experimentally using dose–response studies. The design of the study, the chosen response criterion, and the statistical model affect the requirement estimate. Although considerable experimental work has been carried out to determine the requirements for Lys, Met, Thr, and Trp in growing pigs (and to a lesser extent in sows), little is known about the requirements for the other essential amino acids. Experimental dose–response studies generally focus on the requirement and less on the overall response (i.e. what are the consequences of an amino acid deficiency?). This latter aspect is, to some extent, accounted for in modelling approaches that quantify the response of the animal to the amino acid supply in a dynamic way. The paper describes the origin of ideal protein and illustrates how fundamental concepts of amino acid nutrition have been integrated in practical modeling approaches for the nutrition of growing pigs and sows.

Digestibility of protein and bioavailability of amino acids in foods. Effects on protein quality assessment.

Abstract: A technical report discusses the suitability of amino acid scores (corrected/uncorrected for crude protein digestibility or for amino acid bioavailability) and scores for the relative net protein ratio (RNPR; corrected for differences in rat and human requirements for essential amino acids) in evaluations of food protein quality. A brief review covers the extant literature of these topics, as well as RNPR values of foods, and the relationship between amino acid scores and RNPR values. Copious data are included.

Protein type and caloric density of protein supplements modulate postprandial amino acid profile through changes in gastrointestinal behaviour: A randomized trial

The requirement of leucine and essential amino acids (EAA) to stimulate muscle protein synthesis increases with age. To target muscle anabolism it is suggested that higher postprandial blood levels of leucine and EAA are needed in older people. The aim was to evaluate the impact of oral nutritional supplements with distinct protein source and energy density, resembling mixed meals, on serum amino acid profiles and on gastrointestinal behaviour. Four iso-nitrogenous protein (21 g) supplements were studied containing leucine-enriched whey protein with 150/320 kcal (W150/W320) or casein protein with 150/320 kcal (C150/C320); all products contained carbohydrates (10 or 32 g) and fat (3 or 12 g). Postprandial serum AA profiles were evaluated in twelve healthy, older subjects who participated in a randomized, controlled, single blind, cross-over study. Gastrointestinal behaviour was studied in vitro by looking at gastric coagulation and cumulative intestinal protein digestion over time. The peak serum leucine concentration was twofold higher for W150 vs. C150 (521 ± 15 vs. 260 ± 15 μmol/L, p < 0.001), higher for W320 vs. C320 (406 ± 15 vs. 228 ± 15 μmol/L, p < 0.001), and higher for low-caloric vs. high-caloric products (p < 0.001 for pooled analyses; p < 0.001 for interaction protein source*caloric density). Similar effects were observed for the peak concentrations of EAA and total AA (TAA). In vitro gastric coagulation was observed only for the casein protein supplements. Intestinal digestion for 90 min resulted in higher levels of free TAA, EAA, and leucine for W150 vs. C150, for W150 vs. W320, and for C150 vs. C320 (p < 0.0125). A low caloric leucine-enriched whey protein nutritional supplement provides a higher rise in serum levels of TAA, EAA and leucine compared to casein protein or high caloric products in healthy, elderly subjects. These differences appear to be mediated in part by the gastrointestinal behaviour of these products. ClinicalTrials.gov: NCT02013466.

Nutrient balancing of the adult worker bumblebee (Bombus terrestris) depends on the dietary source of essential amino acids.

ABSTRACTAnimals carefully regulate the amount of protein that they consume. The quantity of individual essential amino acids (EAAs) obtained from dietary protein depends on the protein source, but how the proportion of EAAs in the diet affects nutrient balancing has rarely been studied. Recent research using the Geometric Framework for Nutrition has revealed that forager honeybees who receive much of their dietary EAAs from floral nectar and not from solid protein have relatively low requirements for dietary EAAs. Here, we examined the nutritional requirements for protein and carbohydrates of foragers of the buff-tailed bumblebee Bombus terrestris. By using protein (sodium caseinate) or an equimolar mixture of the 10 EAAs, we found that the intake target (nutritional optimum) of adult workers depended on the source and proportion of dietary EAAs. When bees consumed caseinate-containing diets in a range of ratios between 1:250 and 1:25 (protein to carbohydrate), they achieved an intake target (IT) of 1:149 (w/w). In contrast to those fed protein, bees fed the EAA diets had an IT more biased towards carbohydrates (1:560 w/w) but also had a greater risk of death than those fed caseinate. We also tested how the dietary source of EAAs affected free AAs in bee haemolymph. Bees fed diets near their IT had similar haemolymph AA profiles, whereas bees fed diets high in caseinate had elevated levels of leucine, threonine, valine and alanine in the haemolymph. We found that like honeybees, bumblebee workers prioritize carbohydrate intake and have a relatively low requirement for protein. The dietary source of EAAs influenced both the ratio of protein/EAA to carbohydrate and the overall amount of carbohydrate eaten. Our data support the idea that EAAs and carbohydrates in haemolymph are important determinants of nutritional state in insects.

Whole-body and muscle amino acid composition of Plata pompano (Trachinotus marginatus) and prediction of dietary essential amino acid requirements

Summary Background: knowing the essential amino acid (EAA) requirement values is fundamental to formulate good quality and cost-effective fish feeds. However, such requirements have been established for few fish species. The estimation of amino acid requirements based on amino acid composition of fish is a fast and reliable alternative. Objective: to determine whole-body and muscle amino acid composition of Plata pompano (Trachinotus marginatus) and estimate its EAA requirements. Methods: EAA requirements were estimated using A/E ratios [(Individual EAA ⁄ Total EAA) * 1000]. Results: hystidine, leucine, lysine and phenylalanine were present in higher concentrations in muscle tissue in comparison with the whole-body. On the other hand, arginine, isoleucine, methionine, tryptophan and valine concentration were not different between whole-body and muscle. A/E ratios for Plata pompano determined in the present study are similar to those reported in other fish species, although valine A⁄E ratios were slightly smaller. Conclusion: until dose-response experiments are conducted to precisely determine EAA requirements, the estimated EAA values using whole-body EAA-as proposed in this study-could be used to formulate diets for Plata pompano. Key words: A ⁄E ratio, Carangidae, diet formulation, fish nutrition.. Resumen Antecedentes: conocer los requerimientos de aminoácidos esenciales (EAA) es fundamental para la formulación de raciones rentables y de buena calidad para peces. Sin embargo, dichos requerimientos se han establecido solo para unas pocas especies de peces. La determinación de las necesidades de aminoácidos basada en la composición de aminoácidos de los peces es un método alternativo rápido y viable. Objetivo: determinar la composición de aminoácidos del cuerpo completo y del músculo del Pámpano (Trachinotus marginatus) y estimar sus necesidades de EAA. Métodos: el requerimiento de aminoácidos esenciales se calculó utilizando el índice A/E [(Individual EAA⁄Total EAA) * 1000]. Resultados: la histidina, leucina, fenilalanina y lisina estaban en una mayor concentración en el músculo que en el cuerpo. Por otro lado, arginina, isoleucina, metionina, triptófano y valina no mostraron ninguna diferencia significativa entre la composición del músculo y el cuerpo. Los valores de A/E para Pámpano determinados en este estudio son similares a los reportados para otras especies de peces, pero no los de valina, que fue levemente menor. Conclusiones: hasta que no sean realizados experimentos de dosis-respuesta para determinar con precisión los requerimientos de EAA, el cálculo de los requerimientos de aminoácidos esenciales a partir de la concentración de aminoácidos del cuerpo -como se propone en este estudio- puede ser utilizado en la formulación de dietas para pámpano. Palabras clave: Carangidae, formulación de dietas, nutrición de peces, razón A/E. Resumo Antecedentes: estimar as necessidades por aminoácidos essenciais (AAE) é importante para formular dietas de boa qualidade e com bom custo-benefício. No entanto, poucas espécies de peixes possuem suas necessidades por (AAE) estabelecidas. A determinação das necessidades por (AAE) baseada na composição de aminoácidos do peixe é uma alternativa rápida e viável. Objetivo: determinar a composição de aminoácidos da carcaça e do músculo do Pampo prateado (Trachinotus marginatus) e estimar suas necessidades por (AAE). Métodos: as necessidades por AAE foi estimada usando o índice A/E [(AAE individual⁄AAE total) * 1000]. Resultados: histidina, leucina, lisina e fenilalanina estavam em maior concentração no músculo do que na carcaça. Por outro lado, arginina, isoleucina, metionina, triptofano e valina não apresentaram diferenças significativas entre a composição da carcaça e do músculo. O índice A/E determinado no presente estudo para o Pampo prateado é similar ao reportado para outras espécies de peixe, entretanto o valor do índice A/E para a valina foi ligeiramente menor. Conclusão: até que experimentos dose resposta sejam realizados para determinar com exatidão as necessidades por aminoácidos essenciais, os valores estimados para as necessidades por aminoácidos essenciais usando a composição da carcaça como proposto neste estudo pode ser usada na formulação de dietas para o Pampo prateado. Palavras chave: Carangidae, formulación de dietas, nutrição de peixes, razão A/E.

Biochemical characterisation of the soluble proteins, protein isolates and hydrolysates from oil palm (Elaeis guineensis) kernel

Oil palm kernel proteins have been less well characterised than other seed proteins. Hence, this study characterised the extractable proteins, protein isolate and hydrolysates of defatted oil palm kernel meal to provide information regarding the biochemical properties of oil palm kernel proteins affected by two harvest seasons (2010 and 2011). The defatted oil palm kernel meal and the protein isolate contained 54.8% and 75.6% protein, respectively. The polypeptide molecular mass ranges of the defatted oil palm kernel meal, the protein isolate and the protein hydrolysates were 19–50, 15–50 and 7–12 kDa, respectively. The alkali-soluble glutelin fraction (60%) was the major soluble portion of the oil palm kernel meal, followed by albumin (25%) and globulin (5.7%). The oil palm kernel protein isolate and hydrolysates showed significantly better amino acid profiles than the extractable soluble fractions, meeting all the essential amino acid requirements for infants, preschool children, adolescents and adults. Threonine was not detected in the defatted oil palm kernel meal nor in any of the extractable fractions, while serine was the least abundant detectable amino acid in the protein isolate and hydrolysates. Both the protein isolate and the hydrolysates were rich in cysteine, methionine, valine and lysine. Globulin and albumin were most sensitive to seasonal variations in amino acid composition and protein content. In conclusion, oil palm kernel protein isolate and hydrolysates generated from the defatted oil palm kernel meal can potentially be utilised in the food and health-based industries due to their good amino acid compositions and high protein contents.

Practical supplementation of shrimp and fish feeds with crystalline amino acids

Abstract In 2011, aquaculture accounted for almost 64 million MT of fish, crustaceans and mollusks (FAO, 2012). Fish meal has historically been the protein source of choice in aquatic feeds, but global supplies have reached a plateau making it less available and more expensive. As a consequence, the use of cheaper proteins made from processed plant proteins, byproducts from agriculture, fisheries or the slaughtering of terrestrial production animals was popularized within the aquaculture feed industry. Although these alternative ingredients may contain a crude protein (CP) content comparable to fish meal, they may be less digestible and deficient in one or more of the ten essential amino acids (EAAs). This has required the adoption of more modern formulation approaches which take into account nutrient availability, especially in regard to EAAs. EAA requirements have been established for a number of species of fish and shrimp. Methionine (Met) followed by lysine (Lys) are the first limiting amino acids in plant and rendered animal byproducts. Formulating for EAAs by simply increasing the dietary inclusion levels of the feedstuffs that contain intact sources of the targeted EAAs can lead to overformulated feeds with excessive levels of CP and other nutrients. A more rational approach is to supplement the diet with crystalline amino acids (CAAs). A first step to the application of a nutrient-based formulation approach is knowledge of the digestible EAA content of the ingredients available for use in the formula. It is highly desirable to formulate on a CP, EAA and energy digestibility basis in line with current formulation practices of most modern feed companies. Further expansion of current EAA digestibility values across ingredients and farmed aquatic species will further enable nutrient based formulation. By formulating on an EAA basis across farmed aquatic species, nutritionists have realized least cost formulation opportunities with the use of CAAs which are now available throughout the world at accessible prices. The CAAs mostly used by the animal feed industry, in order of usage, are the following: dl -methionine or Met analogs, l -lysine, l -threonine, l -tryptophan, l -isoleucine and l -valine. Met and Lys are the most currently used due to their wide availability and importance as most limiting EAAs in plant protein ingredients, such as soy and corn based meals. There is a relatively wide variation in the dietary Met and Lys requirement values for farmed fish and shrimp. This is due to differences in species requirements, culture systems, developmental stage and composition of experimental diets. The dietary Met requirements for fish and shrimp range from 0.5 to 1.5% and from 0.7 to 0.9% of the diet, respectively (NRC, 2011). The dietary Lys requirements range from 1.2% to 3.3% of the diet for cultured fish and from 1.6 to 2.1% of the diet for cultured shrimp. Appropriate dietary Met and Lys levels improve the use of other EAAs because they have the ability to reduce the oxidation rate of other amino acids. The present review discusses bioavailability, requirements and sources of EAAs and practical considerations for their application in aquaculture feeds. The appropriate supplementation of crystalline amino acids in feeds for fish and shrimp represents an opportunity to reduce formulation costs in the face of the volatile commodity market of protein ingredients and the short supply of fish meal. Competitiveness in the aquatic animal feed industry today depends upon application of modern and environmentally-sound formulation techniques based on nutrient value and supplementation with crystalline EAA to meet animal nutrient requirements.

Evaluation of methods to estimate the essential amino acids requirements of fish bfrom the muscle amino acid profile

Many methods to estimate amino acid requirement based on amino acid profile of fish have been proposed. This study evaluates the methodology proposed by Meyer & Fracalossi (2005) and by Tacon (1989) to estimate amino acids requirement of fish, which do exempt knowledge on previous nutritional requirement of reference amino acid. Data on amino acid requirement of pacu, Piaractus mesopotamicus, were used to validate de accuracy of those methods. Meyer & Fracalossi's and Tacon's methodology estimated the lysine requirement of pacu, respectively, at 13 and 23% above requirement determined using dose-response method. The values estimated by both methods lie within the range of requirements determined for other omnivorous fish species, the Meyer & Fracalossi (2005) method showing better accuracy.

Branched-chain amino acid requirements for enterally fed term neonates in the first month of life

Knowledge of essential amino acid requirements in infants is important because excessive intake of protein can lead to increased long-term morbidity such as obesity. A deficient intake may lead to suboptimal growth and impaired neurodevelopment. The current recommended branched-chain amino acid requirements in infants aged 0-1 mo are based on the amino acid content of human milk. We quantified the requirements for isoleucine, leucine, and valine for term neonates by using the indicator amino acid oxidation method with [1-(13)C]phenylalanine as the indicator. Fully enterally fed term infants received randomly graded amounts of isoleucine (5-216 mg · kg(-1) · d(-1)), leucine (5-370 mg · kg(-1) · d(-1)), or valine (5-236 mg · kg(-1) · d(-1)) as part of an elemental formula. Data are expressed as means ± SDs. Eighty-three Asian, term neonates (mean ± SD birth weight: 3.3 ± 0.4 kg; gestational age: 39.4 ± 1.3 wk) were studied at a postnatal age of 13 ± 5 d. Mean requirements for isoleucine, leucine, and valine (measured in boys only) were 105 mg · kg(-1) · d(-1) (r(2) = 0.61, P < 0.001), 140 mg · kg(-1) · d(-1) (r(2) = 0.26, P < 0.01), and 110 mg · kg(-1) · d(-1) (r(2) = 0.35, P = 0.001), respectively. Current human milk-based recommendations for isoleucine and valine in term infants aged 0-1 mo are correct. However, the current recommendation for leucine (166 mg · kg(-1) · d(-1)) is higher than the mean requirement of 140 mg · kg(-1) · d(-1) that we determined in this study. This trial was registered at www.trialregister.nl as NTR1610.

Efficacy of quality protein maize in meeting energy and essential amino acid requirements in broiler chicken production

Quality protein maize (QPM), with almost double lysine and tryptophan in protein, is no different from regular maize (RM) in terms of quantity of energy and protein. The objective of the study was to assess whether QPM can substitute RM as an efficient energy source as well as requirement of essential amino acids in poultry feed. Experiments were conducted to determine apparent metabolizable energy (AME), digestible amino acid values, and utilization pattern of QPM and RM in chickens. AME of QPM was similar to RM. Lysine and threonine digestibilities were significantly (P≤0.05) higher in QPM than RM. Dietary replacement of RM by QPM at 50% or higher level significantly improved the body-weight gain. The overall feed conversion ratio (0–40 days) improved significantly in QPM compared to RM at 50% replacement level or higher. Abdominal fat content decreased by 40% and breast meat yield increased by 4.91% by dietary replacement of RM with QPM at 100% level. The protein concentration in serum increased linearly by increasing the level of replacement of RM by QPM. Serum cholesterol decreased significantly in the dietary group where RM was replaced by QPM at 100% level. Neither dressed weight nor giblet weight was influenced by replacement of RM by QPM or supplementing lysine to RM-based diet. However, the breast weight increased and abdominal fat content decreased significantly where RM was replaced by QPM at 50% level or higher. Our findings clearly indicated that feeding value of QPM was higher than RM in broiler chickens.

Peculiarities of one-carbon metabolism in the strict carnivorous cat and the role in feline hepatic lipidosis.

Research in various species has indicated that diets deficient in labile methyl groups (methionine, choline, betaine, folate) produce fatty liver and links to steatosis and metabolic syndrome, but also provides evidence of the importance of labile methyl group balance to maintain normal liver function. Cats, being obligate carnivores, rely on nutrients in animal tissues and have, due to evolutionary pressure, developed several physiological and metabolic adaptations, including a number of peculiarities in protein and fat metabolism. This has led to specific and unique nutritional requirements. Adult cats require more dietary protein than omnivorous species, maintain a consistently high rate of protein oxidation and gluconeogenesis and are unable to adapt to reduced protein intake. Furthermore, cats have a higher requirement for essential amino acids and essential fatty acids. Hastened use coupled with an inability to conserve certain amino acids, including methionine, cysteine, taurine and arginine, necessitates a higher dietary intake for cats compared to most other species. Cats also seemingly require higher amounts of several B-vitamins compared to other species and are predisposed to depletion during prolonged inappetance. This carnivorous uniqueness makes cats more susceptible to hepatic lipidosis.

Nitrogen Retention and Plasma Amino Acid Responses in Mature Geldings Fed Three Dietary Concentrations of Lysine

Six mature Quarter Horse geldings (age, 11.5 ± 4.7 years; body weight [BW], 526 ± 9.2 kg) were used in a replicated 3 × 3 Latin square design to determine the effects of three dietary lysine (Lys) levels on nitrogen (N) retention and plasma amino acid (AA) concentrations. The geldings were fed a basal diet of concentrate and Bermuda grass hay supplemented with synthetic essential amino acids (EAA) to meet estimated requirements for EAA. Geldings were fed one of three dietary treatments: (1) a basal diet deficient in Lys (L−; 0.027 g of Lys•kg−1 BW•d−1); (2) a basal diet supplemented with synthetic Lys to meet National Research Council (NRC; 2007) requirements (L+; 0.036 g of Lys•kg−1 BW•d−1); or (3) a basal diet supplemented at twice the recommended Lys requirement (2 × L; 0.070 g Lys•kg−1 BW•d−1). Horses fed the 2 × L diet had higher N intakes (P = .0056) than horses fed either the L− or L+ diet. However N retention (P = .63) was not different between treatments. Plasma Lys was greater (P < .0001) in 2 × L than L− and L+ diets. Plasma threonine (Thr; P < .01), methionine (Met; P = .03), and total plasma non-EAA (P < .05) concentrations decreased as dietary Lys increased. These results suggest N retention is not a good response criterion for evaluating the AA requirements of mature horses. However, plasma AA data indicated more efficient use of Thr and Met when horses were fed dietary Lys in concentrations greater than the current requirement recommended by the Nutrient Requirements of Horses (National Research Council, 2007).

Quantitative dietary methionine requirement of juvenile golden pompanoTrachinotus ovatusat a constant dietary cystine level

A feeding trial was conducted to determine the dietary methionine requirement of juvenile golden pompano (initial body weight 12.40 ± 0.02 g). Six diets were formulated with six graded levels of methionine (8.6, 9.2, 10.4, 11.5, 13.2 and 14.5 g kg−1). Each diet was randomly assigned to triplicate groups of 20 juvenile fish in seawater floating net cages (1.0 m × 1.0 m × 1.5 m). Fish were fed twice daily (08:30 and 16:30) to apparent satiation for 56 days. Weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), feed efficiency (FE), nitrogen retention efficiency (NRE), proximate body composition, morphometry and haematology were significantly (P < 0.05) affected by the dietary methionine levels. WG, SGR and FE increased with increasing levels of methionine up to 13.2 g kg−1 diet (P < 0.05) and remained nearly the same thereafter. NRE also increased with increasing levels of methionine up to 13.2 g kg−1 diet (P < 0.05) and remained nearly the same thereafter. Linear regression analysis on WG and NRE indicated that the recommended optimum dietary methionine levels for optimal growth of juvenile pompano were 10.6 and 12.7 g kg−1 diet, respectively, corresponding to 24.6 and 29.5 g kg−1 dietary protein, respectively, so the level of dietary methionine should be between 10.6 and 12.7 g kg−1 diet, corresponding to 24.6–29.5 g kg−1 dietary protein. Additionally, the estimated requirements for the other essential amino acids were calculated from A/E ratios of whole-body amino acid profile based on the methionine requirement determined from the present experiment.

Whole body and egg amino acid composition of Nile perch, Lates niloticus (Linnaeus, 1758) and prediction of its dietary essential amino acid requirements

Eggs and tissue of Nile perch juveniles were analysed in order to derive the essential amino acid dietary requirements for Nile perch larvae and juveniles, using the A/E ratio. Results revealed the presence of both essential and non-essential amino acids in Nile perch. A significant difference (p < 0.05) between the amino acids (AA) composition in the eggs and tissue and amongst the four class sizes of juveniles was observed. Estimates of the amino acid dietary requirements revealed that Nile perch has high arginine, leucine, threonine, valine and isoleucine dietary requirements. Key words: Nile perch, amino acids, dietary requirements, larvae, juveniles.

Investigating the appropriate mode of expressing lysine requirement of fish through non-linear mixed model analysis and multilevel analysis

Accurate estimates of lysine requirement are essential to fish feed formulation. However, controversy exists regarding the most appropriate mode to express lysine requirement. In the fish nutrition literature, essential amino acid (AA) requirement has been expressed as a percentage of diet, a percentage of dietary crude protein or a ratio to dietary digestible energy (DE). The controversy lies in the different assumptions regarding the effects of dietary protein and DE on lysine requirement. Non-linear mixed model analysis and multilevel analysis were carried out to investigate whether dietary protein or DE affected lysine requirement of fish. The non-linear mixed model analysis suggests that expressing lysine requirement as a percentage of dietary protein provides a better goodness of fit to the modelling dataset than expressing requirement as a fixed concentration of diet, which in turn is generally better than expressing requirement as a ratio to DE. Results from the multilevel analysis confirm that dietary protein content has a significant effect on lysine requirement, while DE does not. The findings of the present study could contribute to a better understanding of the underlying dietary factors that affect AA requirements of fish. The results of the present study could also be useful for developing nutritional guidelines and feed formulations for fish.

A review of nutritional biology and dietary requirements of redclaw crayfish Cherax quadricarinatus (von Martens 1868)

Redclaw crayfish (Cherax quadricarinatus, von Martens 1868) is a freshwater decapod crustacean with a number of biological and commercial attributes that make it an excellent aquaculture species. The redclaw aquaculture industry has been growing rapidly since the mid-1980s in tropical and subtropical regions of the world. Redclaw aquaculture is mostly in extensive pond systems, but interest in developing more intensive systems is increasing. To support continued intensification, development of high-quality practical diet formulations and information about redclaw nutrition requirements are necessary. A number of studies have determined optimum dietary protein and lipid requirements for juvenile redclaw. However, there is limited information on essential amino acid and fatty acid requirements. Several studies report the presence of various digestive enzymes that have been linked to the ability of the species to digest a wide range of dietary components. Furthermore, as in many other aquaculture species, there is a need to replace fishmeal with other protein sources. A number of studies explored the possibility of replacing fish meal with various terrestrial plant sources of protein and lipids and showed that redclaw can be offered diets containing low-cost, plant-based ingredients without compromising survival, growth and, to a certain extent, reproduction. Formulated diets containing less expensive, plant-based ingredients will contribute to a more profitable and environmentally sustainable redclaw aquaculture industry. Finally, there is also a paucity of information on vitamin and mineral requirements of redclaw and little information on nutrient requirements of broodstock. For the redclaw aquaculture industry to thrive, we need to have a better understanding of nutrient requirements at all life stages.