Influence of dietary non-essential amino acid profile on growth performance and amino acid metabolism of Nile tilapia, Oreochromis niloticus (L.)

Optimisation of trace mineral supplementation in diets for Atlantic salmon smolt with reference to holistic fish performance in terms of growth, health, welfare, and potential environmental impacts

The aquafeed ingredient inventory is ever changing, from marine to plant based, and recently evolving to incorporate increasing amounts of low trophic, side stream and circular economy based raw materials, each one contributing with variable amounts and qualities of macro- and micronutrients. Meeting the micronutrient requirement of farmed fish for healthy and efficient growth under normal and challenging conditions is of paramount importance. In this study we run a trial based on a 2 × 4 factorial design with three replications for each dietary treatment, where Atlantic salmon smolt were fed one of 8 experimental diets supplemented with either organic or inorganic mineral premixes (copper, iron, manganese, selenium, and zinc) at four dietary inclusion levels. We saw a trend for higher growth rate in the organic mineral groups irrespective of the dietary mineral levels. Mineral digestibility was negatively correlated with increasing mineral supplementation levels for all tested minerals but Se which increased with the increasing supplementation in the inorganic and up to the 2nd inclusion level in the organic mineral groups. Increasing mineral supplementation affected retention efficiency of Zn, Mn, Cu and Fe while mineral source affected only the retention of Se which was higher in the organic mineral groups. Moreover, fish obtained higher EPA and DHA in their body and increased slaughter yield in the organic as compared to the inorganic mineral groups and corroborated that trace mineral inclusion levels play a key role on salmon fillet's technical quality. More effects from different origin and dietary inclusion levels of trace minerals were seen on fillet yield, fillet technical and nutritional quality, bone strength, skin morphology, organ mineralization and midgut transcriptome.

Comparative estimation of the lysine requirements in two generations of improved strain of Nile tilapia (Oreochromis niloticus) at the grow-out stage

A 3 × 2 factorial experiment was conducted to investigate the effects of dietary lysine on growth performance, body indices, feed intake, feed efficiency, whole body nutrient composition and amino acid deposition in two successive generations (16th and 17th) of GIFT (Oreochromis niloticus). Three diets containing different levels of lysine at 1.16%, 1.56% and 2.41% were prepared for the feeding trial. Triplicate groups of fish with an initial body weight of 155 g were fed to apparent satiation for 10 weeks in a recirculating aquaculture system. Apparent digestibility coefficients (ADC) of dry matter, crude protein, crude lipids, and total carbohydrates were measured in the experimental diets. At the end of the experiment, no interactions between dietary lysine levels in diet and fish generation were observed on all parameters except for the condition factor (CF) and ADC of crude protein. However, dietary lysine level significantly affected the final weight, weight gain, thermal unit growth coefficient (TGC), protein efficiency ratio (PER) and ADC of dry matter regardless of the fish generation. Final weight, weight gain and TGC of fish were the highest in fish fed 2.41% dietary lysine in diet or 6.52% lysine in the protein. PER was the lowest in fish fed 1.16% dietary lysine. The final weight and the body's accumulation of isoleucine, phenylalanine, and alanine were significantly affected by the fish generation, with the 17th generation having the best performance. Increase growth and higher lysine requirement observed in the improved generation (17th) compared to the (16th) generation at grow out phase indicating that genetic improvement may have changed the dietary lysine requirement.

Amino Acid Requirements for Nile Tilapia: An Update

This review aims to consolidate the relevant published data exploring the amino acid (AA) requirements of Nile tilapia, Oreochromis niloticus, and to reach a new set of recommendations based on those data. There are still inconsistencies in lysine, sulfur-containing AA, threonine, tryptophan, branched-chain AA, and total aromatic AA recommendations in data that have appeared since 1988. This review finds that strain, size, basal diet composition, and assessment method may have contributed to the inconsistencies in AA recommendations. Currently, the expansion of precision AA nutrition diets for Nile tilapia is receiving more attention because of the demand for flexibility in widespread ingredient substitutions which will allow compliance with environmentally sustainable principles. Such approaches involve changes in diet ingredient composition with possible inclusions of non-bound essential and non-essential AAs. Increasing the inclusion of non-bound AAs into Nile tilapia diets may modify protein dynamics and influence AA requirements. Emerging evidence indicates that not only essential but also some non-essential amino acids regulate growth performance, fillet yield, and flesh quality, as well as reproductive performance, gut morphology, intestinal microbiota, and immune responses. Thus, this review considers current AA recommendations for Nile tilapia and proposes refinements that may better serve the needs of the tilapia industry.

Atlantic Salmon (Salmo salar) Performance Fed Low Trophic Ingredients in a Fish Meal and Fish Oil Free Diet

To evolve fish farming in an eco-efficient way, feed production must become less dependent on forage fish-based ingredients and make more use of low trophic level organisms, including microalgae, higher plants, as filter feeding organisms and other ingredients with low competition to established food value chains. Diets nearly free of fish meal and fish oil are not a novelty but are often composed of complex mixtures, containing supplements to meet the farmed animal’s nutritional requirements. Sustaining a growing aquaculture production, maintaining at the same time fish health, welfare, and profitability, and meeting strict environmental and food safety demands, is challenging and requires new technologies, great investments, and more knowledge. A benchmarking feeding trial was performed to demonstrate the main effects of four low trophic raw materials on Atlantic salmon (Salmo salar) growth, metabolism, skin health and fillet quality. To this end, a diet was produced to contain commercially relevant levels of fresh high quality organic FM and FO and was used as a control in the trial (FMFO). Heterotrophically produced Schizochytrium limacinum biomass was used to replace organic FO (HM diet). Spray dried cell wall disrupted biomass of the phototrophically cultured diatom Phaeodactylum tricornutum replaced partly FM and FO (PM diet). Black soldier fly (Hermetia illucens) larvae meal and tunicate (Ciona intestinalis) meal, were used to produce the diets BSFL and TM, respectively, replacing large parts of FM as compared to the FMFO. A fifth test diet was produced combining all test raw materials and removing all FM and FO (0FM0FO diet). All test ingredients were well accepted sustaining high growth rates (TGC values near 4) and feed efficiency (FCR values below 0.9) in salmon showing good gut health and normal metabolic responses. However, none of the treatments reached the growth performance of FMFO. Additional differences between test and control treatments were identified in dietary nutrient apparent digestibility, fish biometrics, blood metabolites and fillet and skin composition. Extensive raw material and dietary chemical characterisation was performed to provide insight on potential shortcomings in the novel low trophic level ingredients which can possibly be overcome combining complementary raw materials.

Mitochondrial Adaptation to Diet and Swimming Activity in Gilthead Seabream: Improved Nutritional Efficiency

Sustained exercise promotes growth in different fish species, and in gilthead seabream we have demonstrated that it improves nutrient use efficiency. This study assesses for differences in growth rate, tissue composition and energy metabolism in gilthead seabream juveniles fed two diets: high-protein (HP; 54% protein, 15% lipid) or high energy (HE; 50% protein, 20% lipid), under voluntary swimming (VS) or moderate-to-low-intensity sustained swimming (SS) for 6 weeks. HE fed fish under VS conditions showed lower body weight and higher muscle lipid content than HP fed fish, but no differences between the two groups were observed under SS conditions. Irrespective of the swimming regime, the white muscle stable isotopes profile of the HE group revealed increased nitrogen and carbon turnovers. Nitrogen fractionation increased in the HP fed fish under SS, indicating enhanced dietary protein oxidation. Hepatic gene expression markers of energy metabolism and mitochondrial biogenesis showed clear differences between the two diets under VS: a significant shift in the COX/CS ratio, modifications in UCPs, and downregulation of PGC1a in the HE-fed fish. Swimming induced mitochondrial remodeling through upregulation of fusion and fission markers, and removing almost all the differences observed under VS. In the HE-fed fish, white skeletal muscle benefited from the increased energy demand, amending the oxidative uncoupling produced under the VS condition by an excess of lipids and the pro-fission state observed in mitochondria. Contrarily, red muscle revealed more tolerant to the energy content of the HE diet, even under VS conditions, with higher expression of oxidative enzymes (COX and CS) without any sign of mitochondrial stress or mitochondrial biogenesis induction. Furthermore, this tissue had enough plasticity to shift its metabolism under higher energy demand (SS), again equalizing the differences observed between diets under VS condition. Globally, the balance between dietary nutrients affects mitochondrial regulation due to their use as energy fuels, but exercise corrects imbalances allowing practical diets with lower protein and higher lipid content without detrimental effects.

Amino acid-specific δ15N trophic enrichment factors in fish fed with formulated diets varying in protein quantity and quality

Compound-specific isotope analysis (CSIA) of amino acids (AAs) in consumer tissues is a developing technique with wide-ranging applications for identifying nitrogen (N) sources and estimating animal trophic level. Controlled experiments are essential for determining which dietary conditions influence variability in N stable isotopes (δ15N) trophic enrichment factors in bulk tissue (TEFbulk) and AAs (TEFAA). To date, however, studies have not independently evaluated the effect of protein quantity and quality (digestibility) on TEFs, complicating the application of AA-δ15N values for estimating trophic levels. We conducted a 98-d feeding experiment using five formulated isoenergetic feeds prepared with a high-quality protein source to evaluate the effect of protein quantity and quality on TEFs of liver and muscle tissues of juvenile Pacific yellowtail (Seriola lalandi), a carnivorous fish species. We decreased protein digestibility using well-established protocols that do not change AA profiles. Growth rates were higher in diets with higher protein content, and isotopic equilibrium was reached for both fish tissues and all treatments. Protein quantity and quality influenced isotope discrimination depending on tissue type and AA. In liver tissue, bulk TEFs showed a limited but significant relationship with protein quality, but did not differ with protein quantity or quality in muscle. None of the pre-established source AAs (Lys, Met, Phe, and Gly) TEFs varied significantly with protein quantity or quality in liver tissue. However, in muscle tissue, TEFPhe increased significantly with protein content and decreased in response to reduced digestibility, indicating it may not serve as proxy for baseline isotopic values used to calculate trophic level. Among trophic AAs, TEFLeu decreased significantly with increasing protein quantity in liver tissue, while both Leu and Ile TEFs decreased with lower protein digestibility in muscle tissue. Our results indicate that CSIA-AA in liver tissue provides more robust source and trophic AA-δ15N values than in muscle.

Effect of dietary macronutrient proportion on intermediate metabolism and oxidative status in sturgeon (Acipenser naccarii) and trout (Oncorhynchus mykiss): comparative study

Three isoenergetic diets varying the proportion of dietary energy supplied by each of the macronutrients (carbohydrate, lipid, or protein) were delivered, to farmed sturgeon (Acipenser naccarii) and trout (Oncorhynchus mykiss), to test the possible effects on the intermediate metabolism and oxidative status in liver, white muscle, and heart. In trout, there is an adaptive metabolic response to an increase in lipids and carbohydrates in the diet. However, this does not happen in the sturgeon. These differences may be due to different dietary habits of both species. In terms of oxidative status, only the liver displayed oxidative stress in both species, showing an increase in the lipid peroxidation and antioxidant enzyme activities after feeding with the high-lipid and high-protein diet.

Effect of N-acetyl cysteine and glycine supplementation on growth performance, glutathione synthesis, anti-oxidative and immune ability of Nile tilapia, Oreochromis niloticus

An 8-week feeding trial was conducted to evaluate the effect of N-acetyl cysteine (NAC) and glycine supplementation on growth performance, glutathione (GSH) synthesis, anti-oxidative and immune ability of Nile tilapia, Oreochromis niloticus. Four practical diets were formulated, control, control +0.2% NAC, control +0.5% glycine, control +0.2% NAC +0.5% glycine. Each diet was randomly assigned to quadruplicate groups of 30 fish (approximately 9.5 g). The weight gain and specific growth rate were significantly increased with the supplementation of NAC and glycine. While they had no effect on feed efficiency feed intake and survival. Glutathion peroxidase (GPx) was increased by NAC and γ-glutamine cysteine synthase (γ-GCS) in plasma were increased by glycine. After the feeding trail, fish were challenged by Streptococcus iniae, fish fed the diet supplemented with NAC obtained significantly higher survival rate after 72 h challenge test. NAC also decreased malonaldehyde (MDA) in liver, increased glutathione S-transferase (GST) activity in plasma, up-regulated mRNA expression of Superoxide dismutase (SOD) and GPx in liver and headkidney. Dietary supplementation of glycine increased the anti-oxidative ability of tilapia through increase anti-oxidative enzyme activity (SOD, glutathione reductase, myeloperoxidase) and up-regulate anti-oxidative gene expression (SOD). Immune ability only enhanced by the supplementation of NAC through increased interleukin-1β (IL-1β) mRNA expression. These results clearly indicated that the supplementation of NAC and glycine can significantly improve the growth performance of tilapia, and NAC also enhance the anti-oxidative and immune capacity of tilapia, glycine could only enhance the anti-oxidative ability.

The effect of dietary amino acid abundance and isotopic composition on the growth rate, metabolism and tissue δ13C of rainbow trout

The aim of the present study was to test whether the dietary non-essential/conditionally essential amino acid composition has an effect on growth and protein utilisation and on δ13C of individual amino acids in rainbow trout (Oncorhynchus mykiss). Trout were reared on six purified diets containing only synthetic amino acids in place of protein. Diet 1 mimicked the amino acid composition of fishmeal, in diet 2, cysteine (Cys), glycine (Gly), proline (Pro) and tyrosine (Tyr) were isonitrogenously replaced by their precursor amino acids serine (Ser), glutamic acid (Glu) and phenylalanine (Phe), and in diet 3, alanine (Ala), asparagine and aspartate, Cys, Gly, Pro, Ser and Tyr were isonitrogenously replaced by Glu. Diets 4, 5 and 6 resembled diets 1, 2 and 3 except that Glu contained 0·1 % 13C-enriched Glu. A control group was reared on a fishmeal-based diet. A total of forty-two trout (4·7 (sd 0·57) g) were fed one of the diets at a level of 3·5 % body mass for 10 weeks in a flow-through system. Dietary non-essential amino acid composition significantly influenced protein gain (P < 0·025) and δ13C of Ala, arginine (Arg), Gly, histidine (His), Phe and Tyr. Non-enriched Glu was predominantly found in trout fed 13C-enriched Glu, which is consistent with the fact that Glu has been shown to be used extensively in the gut as an energy source but is less consistent with the enrichment of Pro in fish fed diet 6 compared with fish fed diet 3. Further research is required to better understand the mechanisms that lead to the alteration of amino acid δ13C between diet and body tissues.

The impact of metabolism on stable isotope dynamics: a theoretical framework

Stable isotope analysis is a powerful tool used for reconstructing individual life histories, identifying food-web structures and tracking flow of elemental matter through ecosystems. The mechanisms determining isotopic incorporation rates and discrimination factors are, however, poorly understood which hinders a reliable interpretation of field data when no experimental data are available. Here, we extend dynamic energy budget (DEB) theory with a limited set of new assumptions and rules in order to study the impact of metabolism on stable isotope dynamics in a mechanistic way. We calculate fluxes of stable isotopes within an organism by following fluxes of molecules involved in a limited number of macrochemical reactions: assimilation, growth but also structure turnover that is here explicitly treated. Two mechanisms are involved in the discrimination of isotopes: (i) selection of molecules occurs at the partitioning of assimilation, growth and turnover into anabolic and catabolic sub-fluxes and (ii) reshuffling of atoms occurs during transformations. Such a framework allows for isotopic routing which is known as a key, but poorly studied, mechanism. As DEB theory specifies the impact of environmental conditions and individual state on molecule fluxes, we discuss how scenario analysis within this framework could help reveal common mechanisms across taxa.

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

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

Determination of underivatized amino acid delta(13)C by liquid chromatography/isotope ratio mass spectrometry for nutritional studies: the effect of dietary non-essential amino acid profile on the isotopic signature of individual amino acids in fish

This study provides data for the effect of dietary non-essential amino acid composition on the delta(13)C values of individual amino acids in rainbow trout (Oncorhynchus mykiss) using liquid chromatography coupled to isotope ratio mass spectrometry (LC/IRMS). In this experiment, trout were reared either on a control diet or on three experimental diets, differing in the composition of non-essential/conditionally essential amino acids, for a period of 6 weeks. The control diet was a commercial trout starter feed with fish meal as the main protein source. The experimental diets contained no protein, only synthetic amino acids. Diet 1 resembled the composition of fish meal in both essential and non-essential amino acids, Diet 2 had all essential amino acids, but cysteine, glycine, proline and tyrosine were replaced by the corresponding amounts of their precursors, and in Diet 3 all non-essential amino acids were replaced by glutamate. LC/IRMS was used for the determination of delta(13)C values of individual amino acids from diets and tissues without derivatization. Diet affected the delta(13)C of individual amino acids in fish. For fish on Diets 1-3 amino acid delta(13)C values showed a similar trend: phenylalanine showed very little change from diet to body tissue. Arginine, lysine, tyrosine and proline showed strong depletion from diet to body tissue and glycine, alanine, aspartate and serine all showed variable but strong enrichment in (13)C. Improvements are necessary before all amino acid delta(13)C values can be determined; however, this study demonstrates that measuring amino acid isotopic signatures by LC/IRMS is a promising new technique for nutritional physiologists.