Intestinal absorption of amino acids in the Pacific bluefin tuna (Thunnus orientalis): in vitro lysine–arginine interaction using the everted intestine system

The interaction between lysine (Lys) and arginine (Arg) in the proximal intestinal region of Pacific bluefin tuna (Thunnus orientalis) was evaluated using the everted intestine method. This in vitro intestinal system has been shown to be an effective tool for studying the nutrient absorption without the need to handle the tuna fish in marine cages as needed for digestibility and amino acid (AA) absorption. We used a factorial design with two sets of variables: low and high Lys concentration (10 and 75 mM) and four different Arg concentrations (3, 10, 20, and 30 mM). Both amino acids were dissolved in marine Ringer solution with a basal amino acidic composition consisting of a tryptone solution (9 mg mL^?1). No interaction was observed between the absorption of Lys and Arg during the first 10 min of the experiment when low concentration of Lys and Arg was used in the hydrolyzate solution. However, there seemed to be a positive effect on Lys absorption when both amino acids were at high concentrations (30 and 75 mM, respectively). This type of studies will led us to test different formulations and/or additives to better understand the efficiency of AA supplementation as an alternative to in situ studies that are difficult to follow to design with the Pacific Bluefin Tuna.     

Comparative intestinal absorption of amino acids in rainbow trout (Oncorhynchus mykiss), totoaba (Totoaba macdonaldi) and Pacific bluefin tuna (Thunnus orientalis)

The kinetics of amino acid absorption in the proximal section of three fish species were studied using an everted intestine technique and a pancreatic digest of casein (Tryptone), as the model amino acid mixture. Fresh intestine of rainbow trout (Oncorhynchus mykiss) was used to set up the experimental system, and results were compared with those obtained using intestines from totoaba (Totoaba macdonaldi) and bluefin tuna fish (Thunnus orientalis). The kinetics of amino acid absorption was sigmoidal for all amino acids and for each species of fish tested. In general, specific absorptions of essential amino acids were higher than those of non‐essential ones. No correlation between the concentration of amino acids in the Tryptone solution and the corresponding absorptions was found. The maximum specific absorption rates of all amino acids for trout were 10 times higher than those determined for totoaba and bluefin tuna. The relative amounts of the different amino acids preferentially absorbed in all three species were different. Results obtained from the everted technique may be applicable to the design of formulated diets for large fish species with commercial value.     

Digestibility of diets containing different soybean meals in Atlantic cod (Gadus morhua); comparison of collection methods and mapping of digestibility in different sections of the gastrointestinal tract

The purpose of the experiment was to evaluate effects of partial replacement of fish meal with soybean meal on digestibility in Atlantic cod and effects of biotechnological processing of soybean meal. Other objectives were to find out if apparent digestibility in cod was affected by age, temperature and/or faecal sampling methods, and to map digestion and absorption patterns along the intestinal tract for different age classes and diets. A control diet with fish meal as the main protein source (FM), a diet with 24% of crude protein from conventional extracted soybean meal (SBM), and a diet with 24% of crude protein from a bioprocessed soybean meal (BP-SBM) were used. Yttrium oxide was added as an inert marker for digestibility determination. The diets were fed to duplicate groups of 534 g (1-year-old) and 1750 g (2-year-old) cod in seawater. Faeces were stripped from the distal-most section (distal chamber) of the intestine after 48 and 84 days of feeding. In addition, intestinal contents were removed by dissection after 84 days. The dissected intestine was divided into 5 sections and contents were analysed separately. Dietary soy did not alter the viscosity of the digesta. The replacement of fish meal protein with soybean protein reduced the apparent digestibility of crude protein, fat, energy and almost all amino acids, independent of type of soybean meal processing. Larger fish had higher digestibility of starch, ash and several amino acids than smaller fish. A temperature decrease from 9.1 °C at feeding day 48 to 6.8 °C at day 84 resulted in lower digestibility of starch, ash and several amino acids. Absorption of amino acids was quantitatively terminated in the distal part of the mid intestine when feeding the soy-containing diets, but continued into the distal chamber when feeding the FM diet. Absorption of fat was completed in the proximal part of the mid intestine when feeding the soy-containing diets, but continued into the middle part of the mid intestine when feeding the FM diet. Soy did not affect absorption pattern of starch along the intestinal tract. Faecal sampling by dissection resulted in higher apparent digestibility of macronutrients than stripping in the 2-year-old cod, and higher apparent digestibility of protein in the 1-year olds.     

Apparent digestibility of protein, energy, and amino acids in some selected feed ingredients for pacu Piaractus mesopotamicus

The apparent digestibility coefficients (ADCs) of amino acids (AA), protein, and energy in six feed ingredients (Brazilian fish meal, soybean meal, corn gluten meal, alcoholic yeast, corn, and wheat bran) we evaluated for pacu juveniles. In general, all ingredients showed high digestibility values for all AA, and differences among ADCs of individual amino acid were detected ( P  < 0.01). Corn gluten, soybean, and fish meals had the highest ADCs of AA. The ADCs of protein in fish meal, yeast, and corn gluten meal should not be used as AA digestibility indicators, because those showed differences up to 6.7% between the ADCs of protein and AA. All ingredients had lower ADCs of energy than corn gluten meal ( P  < 0.01). Lysine was the first limiting amino acid in fish meal, corn gluten meal, wheat bran, and corn, and the second limiting amino acid in soybean meal, as methionine was the first limiting amino acid in soybean meal and yeast. However, the soybean meal was the best quality protein source, as it had the highest digestible essential amino acid index. This demonstrated that digestible amino acid values can be used to formulate practical diets for pacu, preventing potential deficiencies or excess that might cause environmental and economic losses.     

美济礁附近海域3种金枪鱼肌肉成分检测与营养评价

为分析中国南海美济礁附近海域大目金枪鱼(Thunnus obesus)、蓝鳍金枪鱼(T.thynnus)、黄鳍金枪鱼(T.albacares)的营养成分与营养价值,该研究采用国标法检测了3种金枪鱼的水分、蛋白质、灰分、脂肪酸和氨基酸成分及其结构,并进行营养评价.结果显示,3种金枪鱼中黄鳍金枪鱼蛋白质含量最高,蓝鳍金枪鱼...     

Digestibility of nutrients and energy in ingredients for bullfrogs during different phases of development

The ability of frogs to digest dietary nutrients changes with growth, with the animals becoming more or less demanding. The objective of this study was to determine the apparent digestibility coefficients of protein, energy and ether extract of 14 ingredients used in bullfrog diets (spray‐dried blood meal, hydrolysed feather meal, poultry by‐product meal, red blood cell concentrate, tilapia by‐product meal, sardine fishmeal, salmon fishmeal, meat and bone meal, corn gluten meal, soybean meal, corn, wheat bran, soy protein concentrate and soybean oil). A total of 2,325 bullfrogs (Lithobates catesbeianus) in different phases of development were used: early phase (mean weight of 30–50 g), growth phase (80–110 g) and finishing phase (150–200 g). Faeces were collected using the method of dissection. Marked differences in digestibility of the ingredients were observed between the different phases of frog development. Among the ingredients studied, salmon fishmeal and corn gluten meal showed good utilization of the protein (78.9% and 86.7%, respectively) and energy fraction (89.4% and 83.3%, respectively). The salmon fishmeal, poultry by‐product meal, sardine fishmeal, soy protein concentrate, wheat bran and soybean oil exhibited good ether extract utilization (81.2%–92.8%), recommending their use in bullfrog diets.     

Evaluation of apparent digestibility coefficients of individual feed ingredients in spotted rose snapper Lutjanus guttatus (Steindachner, 1869)

Apparent digestibility coefficients (ADCs) for dry matter, crude protein, energy and essential amino acids for five commonly used feed ingredients were determined for juvenile spotted rose snapper Lutjanus guttatus (average body weight 90.6 g). ADCs were determined using the stripping technique to collect faeces after fish were fed a reference diet and test diets composed of 700 g kg^?1 reference diet and 300 g kg^?1 test ingredient. Chromic oxide (Cr₂O₃) was used as an inert indicator. Ingredients tested included sardine fishmeal (FM), canola meal (CM), tuna by‐products meal (TBM), poultry by‐product meal pet grade (PBM‐PG) and solvent‐extracted soybean meal (SBM). In general, all ingredients showed high digestibility values for all essential amino acids, although differences were detected among ingredients. ADC values for dry matter, protein and energy ranged 77.0–80.4%, 84.3–82.5% and 89–88.8%, respectively, for marine ingredient and land‐based animal protein sources, and 75.0–74.2%, 81.5–80.9% and 87.4–86.8%, respectively, for the plant‐based protein source. SBM, TBM and PBM‐PG should be further evaluated in feeding trials as partial FM replacements in rose snapper L. guttatus diets. Knowledge of ADC values for these ingredients will allow feed producers to develop nutritionally balanced, low‐cost feed formulations for this species.     

Capacity for digestive hydrolysis and amino acid absorption in Atlantic salmon (Salmo salar) fed diets with soybean meal or inulin with or without addition of antibiotics

This experiment was done to study the effects of dietary soybean meal (SBM) and inulin (a prebiotic) on the capacity for digestive hydrolysis and amino acid absorption by Atlantic salmon, and how a dietary supplement of the broad-spectrum antibiotic oxytetracycline (OTC) modulated these responses. A control diet (FM) was made from fish meal, fish oil and extruded wheat. Two similar diets were made with 250 g soybean meal (SBM) or 75 g inulin kg^− 1. Each diet was made with or without a supplement of 3 g OTC kg^− 1. All six diets contained yttrium oxide for estimation of apparent nutrient absorption. Each diet was fed to two groups of 172 g salmon kept in 1 m² tanks with 9 °C saltwater for 3 weeks. Intestinal organs were then sampled and weighed. Gastrointestinal tracts (GIT) were sectioned for analyses of brush border alkaline phosphatase (ALP) and leucine aminopeptidase (LAP) activities. Tissue from the distal intestine (DI) was also fixed for histological examination. Digesta from the different sections were freeze dried for estimation of trypsin and amylase activities, and of apparent absorption of amino acids (AA), nitrogen (N), and sulphur (S). About 85% of the trypsin activity, 70% of the amylase activity, 85% of the ALP activity, and 82% of the LAP activity were found in the proximal (PI) and mid (MI) intestine of fish with functional DI, and the absorption of AA, N, and S was quantitatively completed in the MI. Dietary OTC resulted in lower relative liver weight, but apart from increased ALP and LAP activities in DI when feeding OTC in combination with inulin, OTC did not modify the responses to dietary SBM or inulin. Dietary SBM resulted in lower relative liver weight, and induced pathomorphological changes in the DI mucosa, thus lower the ALP and LAP activities in the DI. SBM also stimulated absorption of AA, N, and S in the PI, but at the same time increased the activities of trypsin and amylase in the DI, indicating reduced re-absorption and increased faecal losses of these endogenous enzymes. Dietary inulin did not damage the DI, and stimulated intestinal growth and higher relative mass of the GIT. Inulin without OTC did not affect the hydrolytic and absorptive capacity of the salmon GIT.     

Fatty acid and proximate composition of bluefin tuna (Thunnus thynnus) muscle with regard to plasma lipids

The composition of tail muscle fatty acids from wild and cultured bluefin tuna reared on a diet based on herring and sardine, along with the plasma lipid profile of the farmed individuals, was determined. The total lipid content of farmed bluefin in this study was 0.922 g/100 g or 3.49 g of saturated fatty acids (SAFA), 4.48 g of monounsaturated fatty acids (MUFA), 2.58 g polyunsaturated fatty acids (PUFA) n‐3 and 0.37 g of PUFA n‐6 fatty acids; for wild specimens, it was 0.920 g/100 g, or 2.85 g of SAFA, 4.82 g of MUFA, 2.78 g PUFA n‐3 and 0.27 g of PUFA n‐6 fatty acids. The major fatty acids in this study were 16:0; 16:1, n‐7; 18:1, n‐9 and DHA 22:6, n‐3 acids. The sum of these major components accounted for more than 57% and 80% of the total fatty acids in all the samples of farmed and wild tuna respectively. No significant differences in the proximate composition were demonstrated between farmed and wild samples, except for the energy value, in favour of the farmed tuna. Statistically, glucose tends to increase together with cholesterol (CHOL) and plasma triglyceride, as for these pairs, it showed positive correlation coefficients and P>0.05. Some measured tuna metabolites demonstrated strong mutual correlations, especially GLU, CHOL and TRIG, which are crucial factors in the lipid profile of animals.     

Predicting the occurrence of Atlantic bluefin tuna (Thunnus thynnus) larvae in the northern Gulf of Mexico: building a classification model from archival data

Although bluefin tuna are found throughout the Atlantic Ocean, spawning in the western Atlantic has been recorded predominantly in the Gulf of Mexico (GOM) in spring. Larval bluefin tuna abundances from the northern GOM are formulated into an index used to tune the adult stock assessment, and the variability of this index is currently high. This study investigated whether some of the variability in larval bluefin tuna abundances was related to environmental conditions, by defining associations between larval bluefin tuna catch locations, and a suite of environmental variables. We hypothesized that certain habitat types, as defined by environmental variables, would be more likely to contain bluefin tuna larvae. Favorable habitat for bluefin tuna larvae was defined using a classification tree approach. Habitat within the Loop Current was generally less favorable, as were warm‐core rings, and cooler waters on the continental shelf. The location and size of favorable habitat was highly variable among years, which was reflected in the locations of larval bluefin tuna catches. The model successfully placed bluefin tuna larvae in favorable habitat with nearly 90% accuracy, but many negative stations were also located within theoretically favorable habitat. The probability of collecting larval bluefin tuna in favorable habitat was nearly twice the probability of collecting bluefin tuna larvae across all habitats (35.5 versus 21.0%). This model is a useful addition to knowledge of larval bluefin tuna distributions; however, the incorporation of variables describing finer‐scale features, such as thermal fronts, may significantly improve the model’s predictive power.     

Partial characterization of the digestive enzymes of Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis> under culture conditions

The digestive enzyme activities of Pacific bluefin tuna Thunnus orientalis were evaluated for specific activity and characterized for pH and temperature optima in crude extracts of stomach, caecal mass, and proximal, middle and distal intestine. A higher level of alkaline proteolytic activity was detected in the caecal mass than in the proximal intestine. Total alkaline proteases, trypsin, chymotrypsin and leucine aminopeptidase (LAP) were tested. The temperature and pH analyses showed that proteolytic activity as well as lipase were maximal in the alkaline range, with a maximum at pH 9.0 and at temperatures between 35 and 60°C, except for the pepsin, which showed maximum activity at the same temperatures but in the acid range (pH 3.0). The α-amylase activity showed a broader range in activity, both for pH and temperature, with higher activity over the alkaline pH values and higher temperature. The lipase activity seems to be nondependent on bile salts under our assay conditions, resulting in a significant activity reduction in the presence of bile salts. This knowledge will allow the development of a gastrointestinal model (everted intestine) where food or feed will be hydrolysed with the fish’s own enzymes, a project that is being undertaken in our laboratory as a contribution to the development of novel diets for tuna fish.     

Fish protein hydrolysate affected amino acid absorption and related gene expressions of IGF‐1/AKT pathways in turbot (Scophthalmus maximus)

The effects of fish protein hydrolysate (FPH) on growth, peptide and amino acid (AA) transporters, postprandial free AA and related gene expression of IGF‐1/AKT pathway were evaluated in turbot (Scophthalmus maximus). Three diets were formulated to contain the same low level of fishmeal; meanwhile 0, 45 and 180 g/kg FPH were, respectively, supplemented to the FF (FPH‐free), FL (FPH‐Low) and FH (FPH‐High) diets. Fish fed the FH diet improved the growth compared with the other groups. For peptide and AA transporters, PepT1, B⁰AT1, CAT1 and PAT1 mRNA levels in proximal or distal intestine decreased in fish fed the FH diet. The concentration of free total essential AAs in serum was higher in the FH treatment than that in the FF treatment at 2 and 6 hr after feeding. For IGF‐1/AKT pathway in muscle, IGF‐1, 4E‐BP1 and FoxO1 mRNA levels were the highest in the FH group, whereas IGF‐1R mRNA levels were the highest expression level in the FF group. In conclusion, down‐regulated AAs transport, alleviated the delayed postprandial peak of serum‐free AAs and increased muscle protein synthesis were observed to improve the growth when turbot was fed high FPH level diets containing a high plant protein.     

Decadal variation in the trans-Pacific migration of northern bluefin tuna (Thunnus thynnus) coherent with climate-induced change in prey abundance

Northern bluefin tuna, Thunnus thynnus, apparently spawn only in the western Pacific and a portion of the juveniles migrate to the eastern Pacific. During the past decade, catches of northern bluefin in the eastern Pacific have declined. One possible cause for this decline, proposed by bluefin stock assessment studies, is a decline in the proportion of bluefin that migrate out of the western Pacific. This hypothesis is examined with several indices of the relative abundance of bluefin tuna in the western and eastern Pacific. These indices suggest a decline in the proportion of bluefin migrating to the eastern Pacific since 1977. This period of reduced bluefin migration coincides with a period when a prey of bluefin, Japanese sardine, Sardinops melanosticta, were abundant off Japan. It is hypothesized that in years when sardines are abundant off Japan, a higher proportion of bluefin stay in the western Pacific compared with years when sardines are scarce. Currently, the adun-dance of sardines off Japan is declining. If this decline continues, this hypothesis predicts an increase in bluefin migrating north of Hawaii and into the eastern Pacific.     

Effects of fasting and feeding on plasma amino acid levels in brown trout

Plasma amino acid (AA) levels were analysed at various intervals during fasting and after feeding in juvenile brown trout, Salmo trutta. After 3 days of food deprivation, total plasma AAs decreased significantly (–26% vs. control) due to a fall in the most abundant essential AAs (EAA): branched-chain amino acid (BCAA) and Thr, and there was also a decrease in non-essential AA (NEAA) levels, especially Ala and Asn. After 15 days of fasting, BCAA increased, possibly related to muscle protein mobilization. After 50 days of food deprivation, a significant increase in Gln levels (40% vs. 15 days of fasting) and a decrease in BCAA (–25% vs. 15 days of fasting) was noted. Feeding a commercial trout pellet caused a clear and progressive increase in plasma AA levels. Both EAA and NEAA concentrations peaked at 11 h post-feeding (4068 ± 160 and 4261 ± 239 µM NEAA, respectively) with a greater increase in EAA (+62%) than NEAA (40%) with respect to control values. These data show that changes in the plasma AA pool clearly reflect the nutritional state of fish and help us to understand the complex AA metabolism.     

No apparent differences in intestinal histology of channel catfish (Ictalurus punctatus) fed heat-treated and non-heat-treated raw soybean meal

The histopathologic effects of feeding heat‐treated soybean meal to fingerling channel catfish (Ictalurus punctatus) were studied. Fish were fed one of six diets: a diet containing 450 g kg^?1 commercial soybean meal (CSBM), or diets with the CSBM replaced by non‐heat‐treated raw soybean meal (RSBM0), or RSBM heated at 130 °C for 5 min (RSBM5), 10 min (RSBM10), 20 min (RSBM20) or 40 min (RSBM40). After 10 weeks, tissue samples were taken from the stomach, proximal intestine, distal intestine, liver, pancreas and spleen from fish in each group for histologic examination. Mild necrotic lesions were found in the gastric glands, pancreas and liver of fish in all the groups (treatment and control groups). Hepatic glycogen deposition was also observed in all the groups, and the spleen samples exhibited considerable brownish‐black pigment deposition around the splenic corpuscles and diffuse mild‐to‐moderate congestion in all of the groups. Generally, these histologic effects appeared to be equivocal between all of the groups, and no abnormalities were noted in the proximal or distal intestine. These findings suggest that feeding channel catfish a diet containing 450 g kg^?1 non‐heat‐treated RSBM did not cause severe histologic changes associated with soybean meal anti‐nutritional factors as have been reported in salmonids.     

Gene expression responses to restricted feeding and extracted soybean meal in Atlantic salmon (Salmo salar L.)

We assessed effects of feed restriction and inclusion of 200 g kg^?1 extracted soybean meal in the diet on gene expression in Atlantic salmon using a cDNA microarray (SFA2.0) and real‐time qPCR. The trial lasted for 54 days. Restricted feeding and soybean inclusion reduced the thermal growth coefficient by respectively 51% and 22% compared with fish fed with the fishmeal‐based control diet to satiation. Soybean decreased distal intestinal expression of lysosomal (cathepsins C, D, L, Y and Z) and extracellular proteases while genes involved in responses to cellular stress were up‐regulated. Expression changes of immune genes suggested both pro‐ and anti‐inflammatory regulation. The hepatic responses to soybean and restricted feeding were highly similar, which could be because of negative effects of soybean meal on digestion and nutrient absorption. We observed up‐regulation of ribosomal proteins and down‐regulation of genes involved in lipid and steroid metabolism. Of note, growth reduction in both study groups was associated with coordinated down‐regulation of genes involved in oxidative and cellular stress responses, metabolism of xenobiotics and protein degradation. High expression of stress‐related genes in salmon fed with the control diet suggests that maximum growth rates can be associated with health problems.     

Digestive capacity, intestinal morphology, and microflora of 1-year and 2-year old Atlantic cod (Gadus morhua) fed standard or bioprocessed soybean meal

The objectives of this work were to evaluate how dietary soybean meal (SBM) or a soy meal made by bioprocessing the SBM (BPSBM) to remove anti-nutritional factors affected hydrolytic capacity, amino acid absorption, intestinal morphology, and microflora along the intestinal tract of Atlantic cod at two life stages. Three fish meal based standard cod diets were formulated to contain no soy (FM control), 25% SBM, or 22% BPSBM. Prior to sampling the diets were fed to duplicate groups of 0.5 kg (1-year old) and 1.7 kg (2-year old) cod for a period of 3 months, and the groups reached 0.9 and 2.5 kg, respectively. Digesta was then sampled from different intestinal sections for analyses of trypsin and amylase activity as well as absorption of amino acids, nitrogen, and sulphur. Gastrointestinal sections were sampled for measurements of relative weight (kg^− 1 body weight), and tissues from these sections were sampled for analyses of brush border enzyme (alkaline phosphatase (ALP), leucine aminopeptidase (LAP), and maltase) activity and histological examination. Microflora was sampled from both digesta and the intestinal wall. The SBM diet stimulated relative growth of all gastrointestinal sections except the distal intestine in both age classes. Relative growth of the pyloric intestine was also stimulated by BPSBM. The pyloric caeca and the upper mid intestine were found to be the major sites for enzymatic hydrolysis of protein and starch and for amino acid absorption. Dietary SBM and BPSBM did not alter the activity of trypsin and LAP, but the activity of these enzymes in the proximal intestine was affected by age, being higher in 1-year old than in 2-year old cod. The rate of amino acid, nitrogen, and sulphur absorption along the gastrointestinal tract was not affected by SBM, but was slowed by BPSBM. Dietary SBM or BPSBM did not alter the morphology of the intestinal mucosa in any sections of the cod intestine. The distal-most structure of the intestine, a compartment with inlet and outlet (anus) valves, showed very high microbial colonisation in the mucosal brush border. Inclusion of SBM in the diet changed the intestinal microflora, increasing the population level of transient bacteria in the pyloric and mid intestine, but reducing the population level of adherent bacteria throughout the intestine. To conclude, Atlantic cod appeared to have a robust and flexible digestive system able to adjust to high dietary levels of soy protein meals.     

Use of ideal protein concept for precision formulation of amino acid levels in fish-meal-free diets for juvenile Nile tilapia (Oreochromis niloticus L.)

This study was undertaken in a closed system with Nile tilapia (Oreochromis niloticus) to examine the effects of total replacement of fish meal (FM) by soybean meal. Nile tilapia fingerlings with an average weight of 5.34±0.08 g were hand‐fed one of the five isoenergetic (≈13.5 MJ digestible energy kg^?1) and isoproteic (≈31% of digestible protein) experimental diets to satiation, six times a day during 85 days in eight replicate fibreglass tanks (six fish per tank). The control diet containing FM was substituted by soybean meal, with and without essential amino acids (lysine, methionine and threonine) or dicalcium phosphate supplementation. The supplemental amino acids were added at levels to simulate the reference amino acid profile of Nile tilapia carcass protein, based on the ideal protein concept. The results showed that soybean meal diet supplemented only with dicalcium phosphate was inferior to the control diet with FM and soybean meal diets supplemented with dicalcium phosphate and essential amino acids. Multiple essential amino acids and dicalcium phosphate incorporation in soybean meal diets was associated with performance, whole‐body composition and carcass yield equal to that of the fish fed with the control diet containing FM. These data suggest that a diet with all plant protein source, supplemented with essential amino acids, based on tissue amino acid profile, can totally replace FM in a diet for Nile tilapia, without adverse effects on the growth performance, carcass yield and composition.     

Development of plant‐based diets and the evaluation of dietary attractants for juvenile Florida pompano,Trachinotus carolinus L.

Sustainable and profitable commercial aquaculture production of marine fish species is dependent on the development of sustainable protein sources as substitutes for expensive animal meals such as fishmeal (FM). Previous Florida pompano Trachinotus carolinus studies have indicated that poultry by‐product meal (PBM) and meat and bone meal can be used to produce a FM‐free diet if suitable levels of nutrients (such as taurine) are included in the diets. In this study, we attempted to develop an all‐plant protein diet by removing the animal proteins in practical diets for pompano by substituting back select ingredients. A series of eight FM‐free diets were formulated, four systematically replaced soybean meal (SBM) with soy protein concentrate (SPC) and four replaced PBM with SPC. Based on the results, there is no clear disadvantage to the use of SPC as a replacement for SBM. However, the complete removal of PBM resulted in reduced performance. Two additional growth trials were conducted to supplement additional amino acids including glycine, valine and histidine, a proprietary chemical attractant mix, fish protein concentrate and squid hydrolysate to improve the growth of pompano when fed all‐plant protein diets. The only improvement in performance occurred with the squid hydrolysate. These results demonstrate that using soybean meal, soy protein concentrate and corn gluten meal as the primary protein sources, a plant‐based feed formulation can be developed, but the removal of all animal proteins is not yet feasible.