Cage Culture of Hybrid Striped Bass in Indiana and Evaluation of Diets Containing Three Levels of Dietary Protein1

Culture of hybrid striped bass Morone saxatilis × M. chrysops has been increasing in selected regions of the United States. Because of their thermal tolerance, hybrids may have potential as a new commercial aquaculture species in the Midwest. In these studies, hybrid striped bass were reared in cages located in southern, central and northern Indiana and offered one of three practical diets. Diets contained either 32, 36 or 40% crude protein. Additionally, a preliminary 8 wk laboratory experiment was conducted in which fish were offered the same diets. All diets were formulated to meet the established dietary lysine requirement; optimal levels of other essential amino acids in the diet were predicted by the whole-body essential amino acid profile of hybrid striped bass. In the laboratory experiment, weight gain of fish fed 36% crude protein was significantly higher than those fed either other level of dietary protein. After 205 days, final average weight gains of fish in the field experiment were not significantly different and ranged from 233 to 426 g with an overall average daily gain of 1.6 g/fish/d. Overall survival was 89.1%. Dress-out percentages were 81.2, 69.8, and 34.9% for eviscerated, eviscerated and headed, and fillets, respectively. Those values were not significantly different among dietary treatments or sites. Lipid content of fillets from fish fed 32% dietary crude protein was significantly higher than in fish fed 36 or 40% crude protein.     

Evaluation of Three Soybean Products in Diets Fed to Juvenile Hybrid Striped Bass Morone saxatilis×M. chrysops

Juvenile hybrid striped bass Morone saxatilis×M. chrysops were fed practical diets containing graded levels of either solvent-extracted soybean meal, roasted soybeans, or raw, unprocessed soybeans. Two separate 10-wk studies were conducted; within each study, there were two separate evaluations of soy products. In the first study, weight gain and feed efficiency of fish fed 45% or higher levels of soybean meal were significantly lower than fish fed the positive control diet, while weight gain and feed efficiency of fish fed 30% soybean meal were not significantly different than fish fed the control diet. Fish fed the lowest level of unprocessed soybean (20%) exhibited significantly depressed weight gain and feed efficiency compared to fish fed the control diet. In the second study, weight gain and feed efficiency of fish fed 40% roasted soybeans were significantly lower than fish fed the control diet, but weight gain and feed efficiency of fish fed 20% roasted soybeans were not significantly lower than fish fed the control diet. In both studies, whole body proximate composition values were significantly different among treatments. Whole-body lipid concentrations were significantly higher in fish fed certain levels of soy products, but only at levels above those eliciting depressions in weight gain and feed efficiency. A further evaluation of solvent-extracted soybean meal was conducted with incorporation levels of 20–40% of the dry diet in gradations of 5% with a nutritionally complete mineral premix. Weight gain and feed efficiency of fish fed any level of soybean meal in that study were not significantly different from fish fed a positive control diet. Whole body proximate components were not significantly different between treatments. Unprocessed soybeans apparently have little potential as an ingredient in diets fed to juvenile hybrid striped bass; roasting, or heat treatment, improves their use. Solvent extracted soybean has the potential of supplying the majority of crude protein in diets fed to juvenile hybrid striped bass. Incorporation of complete mineral premixes seems beneficial with higher levels of solvent-extracted soybean meal.     

Apparent digestibility of Asian carp‐ and common carp‐derived fish meals in feeds for hybrid striped bass Morone saxatilis ♀ × M. chrysops ♂ and rainbow trout Oncorhynchus mykiss

Apparent digestibility coefficients (ADCs) of nutrients (crude protein, amino acids, crude lipid, fatty acids, and minerals) were determined for fish meals derived from menhaden, Asian carp (combination of silver and bighead carps), and common carp in feeds for hybrid striped bass and rainbow trout. Extruded test diets were formulated to contain a 70 : 30 mixture of reference diet and test ingredient with yttrium oxide (1 g kg^?1) serving as the inert marker. Diets were randomly assigned to triplicate tanks and fish were fed once per day at 2% body weight. Fecal samples were collected by manual stripping. The ADCs were calculated according to standard procedures. The composition and digestibility of Asian carp and common carp meals was broadly similar to menhaden meal. Protein digestibility ranged from 86.5% (Asian carp meal) to 93.1% (common carp meal). Lipid was highly digestible with ADCs >100% for all ingredients. Although the Asian carp meal was less digestible than the other two fish meals, it was still a highly digestible ingredient. Our data suggest that fish meals derived from Asian or common carp would be valuable feedstuffs in diets for hybrid striped bass, rainbow trout, and possibly other cultured fishes.     

Amino Acid Availability of Four Practical Feed Ingredients Fed to Striped Bass Morone saxatilis

Four dietary protein sources were bio-assayed for amino acid availability, as estimated by true digestibility, when fed to striped bass Morone saxatilis . Diets were formulated to contain either herring fish meal, soybean meal, corn gluten meal or peanut meal as the sole source of dietary protein. A fifth diet, containing no protein, was fed to estimate the level of endogenous amino acids for calculation of true digestibility. The five dietary treatments were randomly assigned to ten tanks of striped bass having an average weight of 150 g per fish. All fish received the assigned diet fed at a rate 1.5% of the biomass per day for a period of 10 d. Fecal samples were collected from anesthetized fish by gentle, manual stripping of the lower digestive tract. Diets and feces were analyzed for dry matter, chromium, nitrogen and amino acid concentrations. There were no statistical differences (P > 0.05) among the protein sources for apparent dry matter digestibility or availability of arginine, threonine, valine and nonessential amino acids with the exception of cysteine. Corn gluten meal had a significantly lower availability coefficient for lysine, and peanut meal had significantly lower availability coefficients for histidine, isoleucine, leucine, and lysine when compared to herring fish meal and soybean meal. Statistically there were no differences between soybean meal and herring fish meal for any nutrient tested. These data suggest that in terms of amino acid availability and overall protein quality, soybean meal could be used to spare herring fish meal in striped bass diets, with corn gluten meal being equally as useful when supplemented with lysine or complemented with other proteins.     

Predicting dietary essential amino acid requirements for hybrid striped bass

Three experiments were conducted that were designed to evaluate our ability to predict essential amino acid (EAA) needs of hybrid striped bass using the quantified lysine requirement and whole‐body amino acid concentrations. In the first experiment, six diets containing various amino acid profiles were fed to triplicate groups of fish initially weighing 7.7 g per fish. At the end of the 8‐week experiment, no significant differences were detected in growth rates or feed efficiencies (FE) between fish fed a practical diet containing 510 g kg^?1 herring fish meal (FM) and fish fed a purified diet containing the amino acid profile of herring fish meal (CAA‐FM). Growth responses of fish fed purified diets containing 100 (HSB), 110 (HSB110), 120 (HSB120) or 140 g 100 g^?1 (HSB140) of the amino acid profile of hybrid striped bass whole‐bodies were significantly lower than those of fish fed diet FM. In the second experiment, triplicate groups of fish (5.6 g per fish) were fed diets containing various energy : protein (E : P) ratios (34.8, 41.2, 47.5 and 53.9 kJ g^?1 protein) and one of two amino acid profiles (CAA‐FM and HSB120) in a 4 × 2 factorial design. Carbohydrate concentration was varied to achieve the desired energy concentrations. At the end of the 8‐week experiment, weight gain and FE were significantly higher in fish fed diets formulated to simulate the amino acid profile of herring fish meal (CAA‐FM) compared with fish fed diets formulated to contain 120 g 100 g^?1 of the amino acid profile of hybrid striped bass whole‐bodies (HSB120). Weight gain, FE and survival data indicated the optimum dietary E : P was 41.2 kJ g^?1 protein. Dietary treatments in the final experiment included three amino acid profiles and four levels of lipid in a 3 × 4 incomplete factorial design. Dietary amino acid treatments included the amino acid profile of herring fish meal (CAA‐FM) or 120 g 100 g^?1 of the predicted EAA requirement profile for hybrid striped bass (HSB120). The amino acid profile of the remaining dietary treatment (PRED+) was similar to that of the HSB120 treatment, but contained additional threonine, isoleucine and tryptophan. Diets CAA‐FM and HSB120 contained either 90, 130, 170 or 210 g kg^?1 lipid, whereas diet PRED+ contained 130 g kg^?1 lipid. Dietary treatments were fed for 10 weeks to triplicate groups of fish initially weighing 81.0 g per fish. Weight gain and FE were not significantly affected by dietary amino acid profile. Feed efficiency was significantly reduced in fish fed diets containing 210 g kg^?1 lipid compared with fish fed diets containing 90–170 g kg^?1 lipid. Intraperitoneal fat (IPF) ratio and hepatosomatic index (HSI) values generally increased as dietary lipid concentrations increased. Total liver lipid concentrations were significantly reduced in fish fed diets containing 210 g kg^?1 lipid compared with those of fish fed 90–130 g kg^?1 lipid. Results of this study indicate an appropriate dietary amino acid profile can be predicted for hybrid striped bass using the quantified lysine requirement and whole‐body amino acid concentrations. Further, the optimum E : P appears to be 40 kJ g^?1 protein.     

The Modification of Poultry By-product Meal for Use in Hybrid Striped Bass Morone chrysops×M. saxatilis Diets

Abstract— A pair of experiments were performed to assess amino acid supplementation of pet food grade poultry by‐product meal for utilization as the sole protein source for hybrid striped bass Morone chrysops×M. saxatilis. The first experiment determined the available amino acids from menhaden fishmeal and poultry by‐product meal for hybrid striped bass. The second experiment determined the efficacy of supplementing poultry by‐product meal with amino acids based on an ideal amino acid profile of hybrid striped bass muscle. The positive control diet contained 40% digestible protein solely from menhaden fishmeal and the negative control diet contained 40% digestible protein solely from pet food grade poultry by‐product meal. The negative control diet was additively supplemented with lysine, methionine, threonine, and leucine at 1.16,0.57,0.31 and 0.47% of the diet, respectively. Lysine supplementation alone did not improve fish performance based on any measured response. Moreover, the negative control diet and the lysine supplemented diet had lower weight gain and feed efficiency than the positive control diet. Supplementation of the diet containing pet food grade poultry by‐product with lysine and methionine; lysine, methionine, and threonine; or lysine, methionine, threonine, and leucine improved weight gain and feed efficiency above that of the negative control diet. The diet containing poultry by‐product supplemented with lysine, methionine, and threonine produced weight gains statistically indistinguishable from those of the positive control diet. Protein and energy retention efficiencies also improved with supplementation of at least lysine and methionine and were statistically indistinguishable from those observed in fish fed the positive control diet. Supplementation with lysine and methionine reduced the hepatosomatic index to levels similar to those found in fish fed the menhaden fishmeal diet. Intraperitoneal fat levels were similar among treatments (6.1‐6.6%) with the exception that fish fed the diet supplemented with lysine, methionine, and threonine exhibited lower (5.5%) fat levels. Supplementing the poultry by‐product meal diet with only lysine and methionine increased muscle ratio to levels equivalent to those found in fish fed the positive control (fishmeal) diet. In conclusion, amino acid supplementation of pet food grade poultry by‐product meal can be used to replace fishmeal in diets for hybrid striped bass without a reduction in fish performance.     

红鳍东方鲀对8种饲料原料的表观消化率

本研究旨在探讨红鳍东方鲀(Takifugu rubripes)幼鱼对红鱼粉、白鱼粉、豆粕、菜粕、花生粕、棉粕、玉米酒糟蛋白(DDGS)和肉骨粉中干物质、粗蛋白、粗脂肪、氨基酸、总能和总磷的表观消化率。实验饲料由70%的基础饲料和30%的待测饲料原料组成,并添加0.1%的三氧化二钇(Y2O3)作为外源添加剂,选取平均体重为37.90 g的红鳍东方鲀幼鱼,随机分成8组,每组3个重复,每个重复30尾鱼,按照不同处理分别投喂相应饲料,采用虹吸法收集粪便。结果显示,白鱼粉、红鱼粉和豆粕的干物质表观消化率分别为70.54%、69.02%和60.37%,显著高于菜粕、棉粕及DDGS(P<0.05);粗蛋白的表观消化率为50.91%~92.78%,肉骨粉粗蛋白表观消化率最低(50.91%),显著低于白鱼粉、红鱼粉、豆粕、菜粕、花生粕和DDGS(P<0.05),各待测饲料原料中总氨基酸表观消化率的变化趋势与粗蛋白的表观消化率基本一致;粗脂肪的表观消化率为70.6%~94.19%,白鱼粉粗脂肪表观消化率最高(94.19%),显著高于棉粕和肉骨粉(P<0.05);能量的表观消化率为30.58%~90.01%,白鱼粉、红鱼粉、豆粕和花生粕总能的表观消化率最高(76.26%~90.01%)(P<0.05);磷的表观消化率为9.13%~68.14%,白鱼粉和红鱼粉的总磷表观消化率最高(分别为66.98%和68.14%)(P<0.05)。白鱼粉、红鱼粉的各种营养成分的表观消化率均较佳,肉骨粉及棉粕各种营养成分的表观消化率相对较差;豆粕及花生粕的粗蛋白消化率及必需氨基酸的消化率优于其他植物蛋白,菜粕次之。     

Utilization of Animal-Protein and Plant-Protein Supplements by Red Swamp Crayfish Procambarus clarkii Fed Formulated Diets1

A study was conducted to evaluate alternative protein supplements that could be used to reduce the cost of formulated crayfish diets. Red swamp crayfish Procambarus clarkii were held in the laboratory for 9 wk and fed 30% crude protein diets containing isonitrogenous mixtures of plant and animal protein in a 65:35 ratio. Combinations tested were: soybean meal/menhaden fish meal (SOY/FSH); cottonseed meal/menhaden fish meal (COT/FSH); soybean meal/meat and bone meal (SOY/MB); cottonseed mealheat and bone meal (COT/MB); soybean meal/meat and bone meal/ blood meal (SOYIMB-B); and cottonseed meal/meat and bone meal/blood meal (COTIMB-B). Comparison of crayfish weight gain, feed efficiency ratio, apparent net protein and energy retention, and body composition indicated that SOY/FSH was the best protein combination tested. Weight gain was reduced when cottonseed meal replaced soybean meal in diets that contained either fish meal or meat and bone meal. Feed consumption of crayfish fed SOY/MB-B and COT/MB-B was lower than that of crayfish fed other diets containing the same plant-protein supplement and weight gain was lower in crayfish fed blood meal in all but one case. Differences in amino acid composition and amino acid availability of protein supplements, inhibitory effects of gossypol in cottonseed meal, and reduced consumption of diets containing blood meal could have contributed to diet effects. Results suggest that soybean meal is a better dietary protein source for crayfish than cottonseed meal, menhaden fish meal is better than meat and bone meal, and both fish meal and meat and bone meal are superior to a 60:40 meat and bone meal/blood meal mixture. However, cottonseed meal, meat and bone meal, and meat and bone meal/blood meal mixtures could be useful as lower-cost alternatives to soybean meal and fish meal in diets for pond-raised crayfish, since the apparent lower protein (amino acid) quality of these ingredients would be unlikely to depress growth of crayfish that have access to natural food in ponds.     

Evaluation of Growth Performance and Whole-body Composition of Juvenile Hybrid Striped Bass Morone chrysops × Morone saxatilis and Red Drum Sciaenops ocellatus Fed High-protein and High-lipid Diets

To investigate potential use of increasing nutritional density of diets for rapid growth of warm‐water fishes, a feeding trial was conducted in which growth performance, body indexes, and whole‐body composition of juvenile hybrid striped bass fed diets comprising protein (49, 54, and 59%), lipid (16, 20, 23, and 28%), and energy (22.0–25.1 kJ/g) concentrations beyond established minimum levels were compared to those of fish fed a more typical commercial reference diet (37.5% crude protein, 10.5% crude lipid, and 19.6 kJ/g energy on a dry matter basis). A subset of the experimental diets and the commercial reference diet also were fed to juvenile red drum. After 6 wk of feeding, hybrid striped bass fed the high‐protein and high‐lipid diets showed much greater growth performance compared to fish fed the commercial diet. Increasing dietary protein level, but not lipid level, tended (P ≤ 0.1) to enhance weight gain and feed efficiency of hybrid striped bass. Hepatosomatic index (HSI), intraperitoneal fat (IPF) ratio, and whole‐body protein were significantly (P < 0.01) influenced by dietary protein level. The dietary lipid and associated energy level had significant negative linear effects on daily feed intake. Linear regression analysis showed that dietary energy : protein ratio, largely influenced by dietary protein level, moderately but significantly influenced weight gain, HSI, IPF ratio, and whole‐body protein of hybrid striped bass and red drum. Red drum grew very similar to hybrid striped bass in response to the experimental diets. However, significant differences in HSI, IPF ratio, whole‐body protein, lipid, moisture, and ash between hybrid striped bass and red drum were observed, indicating species differences in protein and energy partitioning. In particular, the excessive lipid in the diet increased HSI and whole‐body lipid of red drum but not of hybrid striped bass.     

Replacement of fish meal by meat and bone meal in diets for large yellow croaker, Pseudosciaena crocea

A growth experiment was conducted to investigate the effects of replacement of fish meal (FM) by meat and bone meal (MBM) in diets on the growth and body composition of large yellow croaker (Pseudosciaena crocea). Six isonitrogenous (43% crude protein) and isoenergetic (20 kJ g^− 1) diets replacing 0, 15, 30, 45, 60 and 75% FM protein by MBM protein were formulated. Each diet was randomly allocated to triplicate groups of fish in sea floating cages (1.0 × 1.0 × 1.5 m), and each cage was stocked with 180 fish (initial average weight of 1.88 ± 0.02 g). Fish were fed twice daily (05:00 and 17:30) to apparent satiation for 8 weeks. The water temperature ranged from 26.5 to 32.5 °C, salinity from 32 to 36‰, and dissolved oxygen content was approximately 7 mg l^− 1 during the experimental period. Survival decreased with increasing dietary MBM and the survival in the fish fed the diet with 75% protein from MBM was significantly lower than other groups (P < 0.05). There were no significant differences in specific growth rate (SGR) among the fish fed the diets with 0 (the control group), 15, 30 and 45% protein from MBM. However, SGR in the fish fed the diets with 60 and 75% protein from MBM were significantly lower than other groups (P < 0.05). No significant differences in feeding rate were observed among dietary treatments. The digestibility experiment showed that the apparent digestibility coefficients (ADC) of dry matter, protein, lipid and energy of MBM were significantly lower compared with those of FM (P < 0.05). Essential amino acid index was found to be correlated positively with SGR in the present study, suggesting that essential amino acid balance was important. Body composition analysis showed that the carcass protein and essential amino acids were not significantly affected by dietary MBM. The lipid and n-3 highly unsaturated fatty acid (n-3 HUFA) in fish muscle, however, significantly decreased with increasing dietary MBM. These results showed that 45% of FM protein could be replaced by MBM protein in diets of large yellow croaker without significantly reducing growth. It was suggested that the reduced growth with higher MBM was due to lower digestibility and imbalance of essential amino acids.     

Optimal Dietary Protein Concentration for Hybrid Tilapia Oreochromis niloticus × O. aureus Fed All-Plant Diets

There are several estimates of the optimal dietary crude protein concentration for juvenile tilapia fed high quality animal proteins or mixtures of animal and plant derived feedstuffs. In the present study, the optimal dietary crude protein concentration for hybrid tilapia Oreochromis niloticus × O. aureus reared in glass aquaria was determined using diets free of fish meal. Further, initial weight of fish was approximately 21 g, which is the beginning of the growout phase of many commercial operations. The diets contained primarily corn co-products and soybean meal as the sources of amino acids, and were formulated to provide 24, 26, 28, 30, 32 or 34% crude protein. The diets were fed to quadruplicate groups of tilapia for 10 wk. Increasing concentrations of dietary crude protein resulted in proportional improvements in weight gain and feed efficiency up to 30% dietary crude protein. Fish fed 24% dietary crude protein exhibited significantly reduced weight gain compared to fish fed 28–34% dietary crude protein. Protein efficiency ratio (PER) of tilapia was unaffected by dietary crude protein concentration. However, fish fed 28% crude protein exhibited numerically higher PER (2.58) than fish fed other levels of crude protein. Muscle crude protein levels were lower in fish fed diets containing 24–28% crude protein than in fish fed 30% and higher concentrations. Quadratic regression analyses of weight gain and feed efficiency data indicated the optimal dietary crude protein concentration to be 29.65% and 28.33%, respectively, while broken line analyses indicated 27.5 and 27.3%, respectively. Based on weight gain, feed efficiency, PER, and proximate composition data, the authors recommend 28% dietary crude protein as the minimum for hybrid tilapia fed all-plant diets and reared in tanks.     

Total sulfur amino acid requirement of juvenile hybrid striped bass (Morone chrysops×M. saxatilis)

Two separate feeding trials were conducted to determine the total sulfur amino acid requirement of hybrid striped bass. Semipurified diets containing 35% crude protein from fish muscle and crystalline amino acids were supplemented with graded levels of methionine. Each diet was fed to juvenile fish in triplicate aquaria receiving freshwater for 8 weeks. Fish fed the basal diet which contained 0.38% methionine and 0.13% cystine experienced complete mortality within 1 week. Prior to death, some fish fed inadequate methionine were observed to have bilateral cataracts. Weight gain and feed efficiency of fish were significantly (P<0.01) affected by supplemental methionine. Regression analysis of weight gain data using the broken-line model indicated a total sulfur amino acid requirement (±s.e.) of 1.0% (±0.02%) of dry diet or 2.9% of dietary protein.     

Evaluation of Plant and Animal Source Proteins for Replacement of Fish Meal in Practical Diets for the Largemouth Bass Micropterus salmoides

Two feeding trials were conducted with juvenile largemouth bass Micropterus salmoides to evaluate alternative plant and animal source proteins for their ability to replace fish meal in practical diets. The first trial was designed to identify the most promising candidates. The second trial was conducted to evaluate how much of the fish meal could be replaced by those candidates. In Study 1, feed‐trained largemouth bass (3.1 ± 0.7 g) were randomly stocked into 18114‐L glass aquaria at 25 fish per aquarium. Fish were fed one of six experimental diets, each containing approximately 38% crude protein and 10% crude lipid, to apparent satiation twice daily. The control diet (CTL) contained 30% fish meal and 34.5% soybean meal. Diets 2–6 each contained 15% fish meal and at least 34.5% soybean meal with the remainder of the protein made up of either meat and bone meal (MBM), soybean meal (SBM), poultry by‐product meal (PBM), a 50150 mixture of blood meal and corn gluten meal (BM/CG), or 50150 mixture of hydrolyzed feather meal and soybean meal (FMISBM). There were three replicate aquaria per dietary treatment. After 12 wk, there was no significant difference (P > 0.05) among treatments in survival which averaged 92% overall. Only fish fed the PBM or BM/CG diets had average individual weights and feed conversion efficiencies that were not significantly different (P > 0.05) from the control diet (CTL). In Study 2, the formulation of the control diet (CTL) remained the same. Based on their performance in the first trial, PBM and BM/CG were chosen to now replace 75 or 100% of the fish meal. Fish were stocked at an average weight of 6.9 ± 1.7 g. After 11 wk, fish fed diets containing the BM/CG mixture at both levels were significantly smaller (P 5 0.05) than fish fed other diets and at 100% replacement survival was reduced. Fish fed diets containing poultry meal as the primary protein source performed as well as those fed the control diet (CTL). It appears that PBM can completely replace fish meal in diets for juvenile largemouth bass without adverse effects on growth, feed efficiency, or body composition.     

Effect of dietary protein reduction with synthetic amino acids supplementation on growth performance,digestibility, and body composition of juvenile Pacific white shrimp, <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

Two experiments were conducted to evaluate the effect of lowering crude protein level and fish-meal inclusion rate by using commercially available synthetic amino acid supplements in practical diets on the growth performance of Litopenaeus vannamei. In experiment 1, three diets were formulated to assess whether 50% of fish meal could be replaced by soybean meal with synthetic amino acid supplementation. Diet 1 was formulated as the normal control with 20% fish meal and 36% crude protein; diet 2 was the negative control with 34% crude protein and half of the fish meal was replaced with soybean meal; and diet 3 was similar to diet 2 but was supplemented with amino acids to ensure the level of lysine, methionine plus cystine, and threonine similar to that in the diet 1. After a 70-day feeding trial, weight gain and specific growth rate of shrimps fed diet 2 were significantly lower than those fed diet 3, and numerically lower than those fed diet 1. Feed intake of shrimps fed diet 3 was significantly higher than those fed diets 1 and 2. There were no significant differences in feed conversion ratio among shrimps fed different diets. In experiment 2, four diets were prepared with diet 1 as the normal control with 41.26% crude protein, diets 2–4 were formulated to contain 39.81, 38.40, and 35.52% of crude protein with synthetic amino acids were added to simulate the amino acid levels of the diet 1. After a 70-day feeding trial, it was found that reducing dietary crude protein from 41.26 to 35.52% did not affect weight gain or feed conversion ratio. The survival of crude protein 35.52% treatment was significantly lower than other treatments. No difference was observed in body protein, lipid composition, and apparent digestibility coefficient among dietary treatments. Results of this study suggested that dietary crude protein could be reduced from 41.26 to 35.52% in the diets of L. vannamei as long as synthetic amino acids were supplemented.     

The Effects of Substituting Selected Oilseed Protein Concentrates for Fish Meal in Rainbow Trout Oncorhynchus mykiss Diets

Three oilseed protein concentrates (soybean, canola, and sunflower) were evaluated to determine their potential, when supplemented with deficient essential amino acids, to partially or completely replace fish meal in diets fed to rainbow trout Oncorhynchus mykiss . Triplicate aquaria of juvenile trout (average weight of 12 g) were fed the experimental diets for 10 wk, at which time the average weight of the fish was approximately sixfold higher than the initial weight. Average fish weight gains on diets in which the protein component was 100% fish meal; 75% fish meal, 25% soybean protein concentrate; 50% fish meal, 50% soybean protein concentrate; and 75% fish meal, 25% sunflowerseed protein concentrate were not significantly different ( P < 0.05). The average weight of fish fed a commercial feed was significantly lower than that of fish fed the 100% fish meal diet, but not significantly different from fish fed the three other formulations mentioned above. Fish fed diets containing 50% fish meal, 50% canola protein concentrate; and 25% fish meal, 75% sunflowerseed protein concentrate had significantly lower average final weights than those of fish fed the other diets. Feed conversion ratio patterns among the dietary treatment groups reflected those of weight gain. Fish survival exceeded 95% on all diets. Apparent protein digestibility coefficients ranged from 79.5% (75% soybean protein concentrate, 25% canola protein concentrate) to 90.6% (100% soybean protein concentrate). The results of this study demonstrated that certain oilseed protein concentrates have good potential as protein sources in rainbow trout feeds when properly supplemented with essential amino acids.     

Dietary Zinc Requirement of Hybrid Striped Bass,Morone chrysops×Morone saxatilis,and Bioavailability of Two Chemically Different Zinc Compounds

Zinc is a trace mineral element that plays an essential role in numerous biochemical processes, and has been shown to affect growth and health of several fish species. However, the dietary zinc requirement of hybrid striped bass has not been defined. Therefore, a feeding trial was conducted to determine the dietary requirement for zinc by this fish and to compare zinc bioavailability of two chemically different forms (zinc sulfate and zinc proteinate). Six experimental diets were formulated with purified ingredients and supplemented with ZnSO₄ to provide total zinc concentrations of 7, 12, 16, 26, 42, and 80 mg/kg diet which were determined by analysis. Each diet contained 32% crude protein, 6% lipid, and approximately 14.2 kJ of digestible energy per gram. The experimental diets were fed twice daily for 10 wk to triplicate groups of 15 hybrid striped bass initially weighing 0.86 ± 0.05 g/fish in 38‐L glass aquaria, connected as a recirculating system. Finally, after the feeding period, the fish were evaluated for weight gain, feed efficiency, protein efficiency ratio, and survival, as well as blood serum zinc, bone zinc, and hematocrit. All fish thrived during the feeding trial and not even the fish fed the basal diet displayed any apparent deficiency signs, although weight gain steadily increased with escalating levels of dietary zinc up to 42 mg/kg diet. On the basis of the most responsive indicators–bone zinc and serum zinc–the minimum dietary zinc requirement of hybrid striped bass was determined to be 17.0 and 17.3 mg Zn/kg diet, respectively, based on broken‐line regression. This estimate is similar in magnitude to dietary zinc requirements reported for other fish species. In addition, the bioavailability of zinc proteinate versus that of ZnSO₄ was estimated by deriving the ratio of the slopes of the regression lines fitted to bone zinc and serum zinc data. This analysis indicated that hybrid striped bass utilized zinc proteinate ～1.7 times more efficiently than ZnSO₄.     

Minimizing Fish Oil and Fish Meal with Plant‐based Alternatives in Sunshine Bass Diets without Negatively Impacting Growth and Muscle Fatty Acid Profile

We determined whether canola oil could spare menhaden oil (MO) in diets containing minimal fish meal without affecting sunshine bass, Morone chrysops × Morone saxatilis, production. Seven isonitrogenous, isocaloric (41.7% crude protein and 14.6% crude lipid) diets containing graded levels (0, 20, 40, 60, 80, or 100%) of menhaden to canola oils with 20% menhaden meal (MM) or 100% canola oil with 20% lipid‐extracted MM were fed to sunshine bass (initial weight 9.3 ± 0.16 g; mean ± SD) twice daily to apparent satiation for 10 wk. Sunshine bass fed less than 40% of their dietary lipid as MO exhibited significantly (P < 0.05) lower feed intake and growth rates. Increased concentrations of saturated, n‐3, and n‐3 highly unsaturated fatty acids (FA) in the fillet were associated with MO‐rich diets, while monounsaturated and n‐6 FA were most common in fillets from fish fed diets rich in canola oil. Reducing MO to 40% of the dietary lipid in diets containing minimal fish meal allows for efficient utilization of marine resources without negatively impacting juvenile sunshine bass production.     

Apparent digestibility coefficients of feed ingredients and their predictability in compound diets for gilthead seabream, Sparus aurata L.

Apparent digestibility of crude protein, amino acids, lipid, carbohydrate and energy was measured for a range of feed ingredients fed to gilthead seabream, Sparus aurata L. — fish meal, poultry meal, meat meal, blood meal, squid meal, extracted soyabean and wheat flour. Chromic oxide was used as a non-absorbed reference substance and faeces were collected by stripping. Diets compounded from mixtures of these ingredients were then used to examine the possibility of predicting the digestibility of formulated diets.
Apparent digestibility of crude protein ranged from 79% to 90%, lipids from 83% to 95% and energy from 72% to 88% in the different ingredients. Apparent digestibility of carbohydrates was lower and ranged from 49% to 77%. Apparent digestibility of amino acids was higher than that of crude protein and differences were found among digestibilities of individual amino acids.
Tests conducted using five compound diets indicated that ingredient digestibility was additive for protein, amino acids, lipids and energy, whereas the digestibility of carbohydrates in the compound feeds was slightly lower than predicted.
Diets for Sparus aurata may thus be formulated on the basis of digestibility of individual ingredients.     

Evaluation of Poultry By‐product Meal in Commercial Diets for Hybrid Striped Bass,Morone chrysops ♀ × Morone saxatilis ♂, in Pond Production

The efficacy of replacing fish meal with petfood‐grade poultry by‐product meal (PBM) on an ideal protein basis in commercial diets for hybrid striped bass (HSB) was evaluated under production conditions in pond 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 fish meal 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, 70, or 100% of fish meal in the GEN diet with PBM on a digestible protein basis and then supplementing with Met and Lys (designated 35PBM, 70PBM, and 100PBM, respectively) as needed to maintain concentrations equal to those in the GEN + AA diet. Diet formulation and extrusion were conducted by a commercial mill, and all diets met or exceeded known nutritional requirements for HSB. Twenty 0.10‐ha ponds (4 ponds/diet) were randomly stocked with juvenile HSB (76 ± 10 g; mean ± SD) at a density of 7400/ha and fed for 600 d (October 2004 to May 2006). Diets were fed once daily to apparent satiation to a maximum of 95 kg feed/ha. Total weight and number of fish in each pond were determined at harvest. Weight distributions in each pond were estimated by selecting every 15th fish during harvest. Subsets of ten fish from each of these samples were selected randomly for the determination of body composition and nutrient and energy retention. The availability of indispensable amino acids as well as ammonia production from the commercial test diets were determined in separate tank trials. Most production characteristics were not statistically different (P > 0.10) among dietary treatments. Distributions of individual fish weights from each of the ponds were not affected by poultry by‐product level in the diet. Multivariate analysis of body compositional indices grouped diets into two clusters composed of GEN, GEN + AA, 35PBM vs. 70PBM, and 100PBM mainly because fish fed the 70PBM and 100PBM diets had greater (P = 0.001) body fat (visceral somatic indices) than fish fed the other diets. Ammonia production in tanks was not different among diets and peaked 6–8 h after feeding when fish were fed at 1.5% of body weight; ammonia‐N excretion ranged from 197 to 212 mg/kg/d and 18.5–21.5% of nitrogen intake. Some imbalances in the levels and ratios of selected amino acids to Lys were found in the diets containing higher amounts of PBM and were attributed to a lack of accurate availability coefficients during formulation for some dietary proteins. These imbalances in essential amino acids may have been the predominant factor in the somewhat fattier fish observed fed diets containing the two highest levels of PBM. Nevertheless, these results from fish stocked at commercial densities and raised to market size in ponds suggest that formulating diets on an available amino acid basis for all protein sources while balancing limiting amino acids, particularly Met, Lys, Thr, and Trp, on an ideal protein basis will yield significant improvements in HSB performance when fed commercial diets in which all fish meal is replaced with PBM.     

The effect of dietary protein level on the apparent digestibility coefficient of two selected feed ingredients for Nile tilapia,Oreochromis niloticus L.

The effect of dietary protein level on the apparent digestibility coefficient (ADC) of meat and bone meal and rapeseed meal for Nile tilapia Oreochromis niloticus L. was examined. Three reference diets were formulated to contain 240 (RD24), 350 (RD35) and 450 (RD45) g kg^?1 crude protein, and chromic oxide was added at 10 g kg^?1 in the reference diets as an inert indicator. Six test diets were formulated by mixing one of the reference diets with each test ingredient at a ratio of 70:30. Fish (initial body weight 101.0 ± 0.6 g) were fed reference diets for 3 days and then fed test diets in the following 4 days cyclically for 4 weeks. Faeces of fish fed each reference diet or test diet was collected from the third day of each diet conversion. Dietary protein level significantly affected the ADC of protein and energy of reference diets, test diets and test ingredients. The ADC of protein and energy of meat and bone meal and rapeseed meal was the highest when these ingredients were mixed with diet RD35. The scope of variation in the ADC of protein and energy of meat and bone meal was 8% (from 69.9% to 78.3%) and 8% (from 70.2% to 78.0%), and the scope of variation in the ADC of protein and energy of rapeseed meal was 4% (from 79.8% to 83.3%) and 5% (from 56.0% to 60.7%) when the dietary protein level was increased from 300 to 480 g kg^?1. This indicates that the ADC of protein and energy of meat and bone meal and rapeseed meal for Nile tilapia varied considerably at different dietary protein levels.