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Abstract Given tilapia grown in the biofloc technology production system can consume the biofloc, it should be possible to optimize formulated diet protein content to account for nutrition derived from consuming biofloc. The present study, conducted in an outdoor biofloc technology production system, evaluated impacts on fish production indices, common microbial off-flavors, and water quality dynamics for hybrid tilapia (Oreochromis aureus × O. niloticus) fed diets formulated to contain 22.5%, 27.7%, and 32.3% digestible protein (DP) and 6% lipid. Fingerlings (32.2 ± 10.1 g/fish) were stocked in tanks (18.6 m2; 16.6 m3) in May 2016 at 25/m2 (29/m3) and grown for 5 months to market size. At harvest, fish fed the 22.5% DP diet were significantly smaller (518 g/fish) and had significantly higher feed conversion (1.5) than those fed the higher DP diets (553–564 g/fish and 1.4, respectively). Feed nitrogen input and nitrification rate increased linearly with increased DP. Results of this study suggest that by using ideal protein theory to formulate diets supplemented with the first four limiting amino acids (Lys, Met, Thr, Ile) digestible protein can be reduced from 32.3% to 27.7% without adversely affecting hybrid tilapia productivity indices. Market size distributions, nutrient retention, 2-methylisoborneol and geosmin off-flavors, and pond water quality dynamics in relation to diet DP also are discussed. Highlights • Dietary intact digestible protein for tilapia in the biofloc system may be reduced from 32.3% to 27.7%, but not to 22.5%. • Market-size frequency distribution of tilapia fed the 22.5% digestible protein diet was skewed toward smaller size classes. • Fillets of tilapia grown in an outdoor biofloc technology production system were tainted by 2-methylisoborneol and geosmin. [ABSTRACT FROM AUTHOR]

We determined if ideal protein (IP) fishmeal-free (FMF) or all-plant protein (PP) diets of available ingredients satisfied production needs of hybrid striped bass (HSB; Morone chrysops x M. saxatilis) grown to market size in ponds managed according to industry practices, and if phytase (Phy) superdosing (20,000 FTUs) could alleviate inorganic phosphorus supplementation. An off-the-shelf commercial feed (COM), an IP control diet containing 16% fishmeal (FM), and four IP test diets with or without phytase superdosing (FMF, FMF + Phy, PP, PP + Phy) were evaluated. Inorganic phosphorus was excluded from phytase treated diets. Hybrid striped bass (averaging 344 g/fish) were stocked (5187 fish/ha) in 4 ponds/diet (0.1 ha) and grown for 5.5 months. Most responses of the five ideal protein diets did not differ significantly (P > 0.1) from the COM. Only net fish yield, weight gain, and FCR of the PP diet were less than those of the COM diet. Fish fed FMF and FMF + Phy diets had higher fish yields, mean weights, and gains than PP and PP + Phy diets. FMF ponds had fewer than expected large (907–1134 g) and more jumbo (>1135 g) fish and FMF + Phy ponds had fewer medium (680–906 g) and more large fish. PP ponds had fewer than expected jumbo fish. The COM diet resulted in larger livers (HSI), lower muscle ratio, but less feed phosphorus added to ponds compared to the FM diet. Absence of differences for other responses confirms the FM diet is a valid proxy for the COM diet. Phytase increased energy and protein retention of the PP diet but not the FMF diet. FM can be replaced with animal and/or plant proteins exclusively without major reductions in hybrid striped bass performance. The PP diet likely requires optimization of Met and branched chain amino acid levels to improve performance. Inorganic phosphorus can be replaced by diet phytase top-coating and judicious inclusion of phytate‑phosphorus without negative impact on HSB production. Phytase superdosing of the FMF and PP diets did not improve production variables but did improve mineral retentions, more so for the PP diet. Phytase superdosing reduced feed phosphorus fed by 60% and pond phosphorus loading by 40% but requires optimization of inclusion levels and economic evaluation before recommendation. • Hybrid striped bass can be grown to market size on an all-plant protein diet. • Dietary fishmeal was replaced totally by plant proteins or animal plus plant proteins. • Dietary inorganic P was replaced totally by phytase top-coating. • Dietary phytase reduced feed P fed by 60% and pond P loading by 40%. [ABSTRACT FROM AUTHOR]

In previous work, we demonstrated that diets containing 40% digestible protein (DP) (45% crude protein) and 18% lipid supplemented with Met and Lys resulted in superior performance and nutrient retentions in hybrid striped bass (HSB) compared to less energy-dense diets when rearing HSB at temperatures similar to the summer growing period of the Southern U.S. The current work was aimed at vetting previous results in pond production of market-size HSB at commercial stocking densities to assess impacts on fish production indices and water quality parameters. Diets were formulated to contain digestible protein levels ranging from 41% to 35% DP and 15% crude lipid. The trial was conducted during the hottest portion of the growing season when impacts of feeding have the greatest influence on pond water quality. The 6-month pond (0.1 ha; 0.25 ac) study began with advanced juveniles (121.4 ± 3.21 g/fish; mean ± SD) in May 2013 and concluded with market sized fish in October 2013. Final fish size ranged from 448 ± 24 g to 1122 ± 46 g with food conversions ranging from 1.34–1.37. Results suggest that DP can be lowered from 41% DP to 35% DP by careful diet formulation while supplementing the first three limiting amino acids (Met, Lys Thr) without detrimental changes to body composition or nutrient retentions. Market size distributions, nutrient retention, and pond water quality dynamics in relation to test diets are also discussed. [ABSTRACT FROM AUTHOR]

Abstract: Substitution of fishmeal with alternate proteins in aquafeeds often results in dietary imbalances of first-limiting essential amino acids (EAA) and poorer fish performance. This growth trial was undertaken to test the hypothesis that ideal protein theory accurately predicts first-limiting amino acids and optimum lysine level for a fishmeal-free, commercial-grade diet formulated for hybrid striped bass (HSB). The ideal model for formulation was the amino acid pattern of hybrid striped bass muscle. A negative control diet based on soybean (45%), corn gluten (10%), and poultry by-product (13%) meals was formulated on an ideal basis to contain 18% lipid, 40% crude protein (CP), 36% digestible protein (DP) and 1.8% Lys from intact sources. Met and Thr were then added at levels equivalent to 40% protein from HSB muscle to form a basal diet that was fortified with seven levels of Lys (2.2 to 6.4g/g diet) that bracketed the predicted ideal Lys requirement (3.5g/g diet) for this formulation. Diets were extruded to achieve similar characteristics as a commercial-grade feed and fed to juvenile fish (118g BW) for 84 d. Response data were subjected to polynomial and exponential regression and the best model per response selected based on the lowest error (MSE) and p-values and the highest adjusted R2. Selected models were used to derive dietary Lys levels required to reach 95% (R95) or 99% (R99) of the minimum or maximum response. Final fish weights (328–369g) increased linearly with increasing dietary Lys. Weight gain, average daily feed intake (1.42–1.7%), and feed efficiencies at 4-, 8-, and 12-week intervals were modeled by cubic functions that yielded consistent R95 and R99 levels of about 2.4 and 4.3g Lys/g diet, respectively. These values evenly bracketed the predicted ideal Lys requirement. Slightly higher Lys requirement was found for optimum FE at 4weeks and smaller fish, as opposed to 8 or 12weeks and larger fish. Whole body composition was unresponsive to diet Lys level; however, higher dietary Lys was required to minimize liver size (4.8 to 5.2g Lys/g diet) than to minimize body fat (2.5 to 3.1g Lys/g diet) or maximize muscle ratio (1.8 to 3.9g Lys/g diet). Whole body protein, lipid, energy, and EAA retentions were also consistent with cubic functions that generally confirmed the predicted ideal Lys requirement with notable exceptions. Retention of Lys decreased exponentially with increasing dietary Lys, whereas, Met retention decreased in a linear fashion, corroborating that Met was first-limiting in this diet formula, as predicted. Retention of Thr and branched-chain amino acids were optimized at higher Lys levels (3.9–4.5g/g diet) than those required to maximize growth parameters. Protein accretion (g/fish/d) responded quadratically to Lys intake predicting maximum deposition at 0.10 to 0.16g Lys/fish/d. Histological assessment of intestines in fish fed these high-soybean meal test diets did not reveal any lesions associated with enteritis for any diet and overall normal intestinal morphology was observed in all fish sampled. [Copyright &y& Elsevier]

Abstract: Lysine is the reference essential amino acid in fish feeds and usually the most limiting amino acid in feedstuffs. The dietary lysine requirement of juvenile pacu Piaractus mesopotamicus (4.3g) was determined using five isonitrogenous (32% CP) test diets containing graded levels of lysine (0.9, 1.17, 1.44, 1.69 and 1.96% of dry diet) fed three times a day to four groups of 18 fish for 74days. Growth, body composition, nutrient retention and hematological parameters of pacu were analyzed. Analysis of variance showed that all growth performance parameters were significantly affected by dietary treatments. The lysine requirements estimated using regression analysis for maximum weight gain and feed efficiency were 1.45 and 1.51% of dry diet, respectively. Nitrogen retention efficiency increased with increasing levels of dietary lysine up to 1.43% (p <0.05). Whole-body protein increased (p <0.05) and whole-body lipid decreased (p <0.05) with increasing dietary lysine level. Thus, the lysine requirement of juvenile pacu was estimated as being 1.4–1.5% of dry diet or 4.4–4.7% of dietary protein. [Copyright &y& Elsevier]

Abstract: A study was undertaken to establish the optimum dietary essential amino acid (EAA) profile for gilthead seabream juveniles based on the amino acid (AA) deletion method. For that purpose 11 diets were formulated to be isonitrogenous (6.72% N) and isolipidic (18%). In the control diet half of the nitrogen was provided by protein bound-AAs (fish meal) and the other half by a mixture of crystalline L-AAs. The overall AA profile of this diet was made similar to that of fish meal protein. Ten other diets were formulated identical to the control except for the deletion of 45% of a single EAA in each diet and by adjusting the nitrogen level with a non-essential AA mixture. Each diet was assigned to four groups of 22 fish (initial body weight of 4.6 g) and the trial lasted 43 days at a water temperature of 25 °C. Fish were fed by hand, twice daily, using a pair-feeding scheme. At the end of the trial the relationship between nitrogen gain and AA intake of the test and control diets was determined. Based on these data, and assuming that nitrogen retention responds linearly to dietary EAA content when a given AA is limiting, the quantity of each EAA that can be removed from the control diet without affecting nitrogen retention was computed and the ideal dietary EAA profile for gilthead seabream juveniles was estimated. Expressed relative to lysine (=100) A/E ratios were estimated to be: arginine, 108.3; threonine, 58.1; histidine, 36.8; isoleucine, 49.7; leucine, 92.7; methionine, 50.8; phenylalanine+tyrosine, 112.3; valine, 62.6; and tryptophan, 14.6. This EAA profile correlates tightly to the whole-body EAA composition of gilthead seabream (R 2 =0.99; p >0.001). [Copyright &y& Elsevier]

Abstract: The efficacy of replacing fishmeal with petfood-grade poultry by-product (PBM) on an ideal protein basis in commercial diets for hybrid striped bass (HSB) was evaluated under production conditions in tank culture. A generic production diet (GEN) for HSB was formulated to contain 45% protein, 12% lipid and 3.7 kcal/kg. Protein in the generic diet was supplied by a mix of animal and plant sources typically used by the industry that included more than 20% select menhaden fishmeal and less than 10% PBM. A positive control diet (GEN+AA) was formulated by supplementing the generic diet with feed-grade Met and Lys to match the level of those amino acids in HSB muscle at 40% digestible protein. Substitution diets were formulated by replacing 35% or 70% of fishmeal in the GEN diet with PBM on a digestible protein basis and then supplementing with Met and Lys (designated 35PBM and 70PBM, respectively) as needed to maintain concentrations of Met and Lys equal to those in the GEN+AA diet. Diet formulation and extrusion were conducted by a commercial mill. Fish were stocked (87 g average initial weight) in three replicated production-scale recirculating culture systems. Diets were initially fed at 4% body weight·day−1 divided into morning and evening feedings and gradually decreased to 1.5% body weight·day−1 during the 24-week trial. The availability of indispensable amino acids (IAA) in the commercial test diets were determined in a separate trial. All test diets were replete with respect to published requirements of hybrid striped bass; however, available levels of Arg and Thr were first- and second-limiting, respectively, and His was third-limiting, in the replacement diets when compared to the IAA profile of hybrid striped bass muscle. Diet composition significantly (P <0.05) influenced final weight, weight gain, yield, hepatosomatic index (HSI) and intraperitoneal fat (IPF) ratio, but did not significantly alter feed conversion and muscle ratio. Generally, fish fed the 35% replacement diet (35PBM) performed as well as fish fed the generic diet, whereas fish fed the 70PBM diet not. Fish fed the supplemented generic diet (GEN+AA) outperformed fish fed the other test diets. Results clearly demonstrate that formulation on an available amino acid basis can significantly improve the performance of current diets for HSB and that petfood-grade poultry by-product can successfully provide nearly half the protein in commercial HSB diets when substituted for fishmeal on an available amino acid basis. [Copyright &y& Elsevier]