Response of Largemouth Bass Micropterus salmoides to Dietary Supplementation of Lysine, Methionine, and Highly Unsaturated Fatty Acids

Abstract.— A 12-wk feeding trial was conducted in aquaria with juvenile (36.0 ± 1.2 g) largemouth bass Microptents salmoides to examine the effects of dietary supplementation of methionine, lysine, and long-chain polyunsaturated fatty acids (PUFA) on growth, feed conversion and body composition. Diets were formulated to increase dietary concentrations of methionine. lysine, and PUFAs to match levels found in whole body samples of largemouth bass. The control diet was formulated similar to diets previously tested for largemouth bass. Diets 2 and 3 were similar to the control diet hut were supplemented with 2% lysine and 1% methionine, respectively. Diet 4 was formulated to increase PUFAs, especially docosahexaenoic acid (DHA) (22:6n-3), by replacing menhaden fish oil with squid oil. Fish were fed all they would consume in 10 min, twice daily. At harvest, there were no statistically significant differences ( P > 0.05) in average individual weight or specific growth rate (SGR) among fish fed the four diets. The feed conversion ratio (FCR) of largemouth bass fed the diet supplemented with methionine (1.7) was significantly lower ( P ≤ 0.05) than fish fed the control diet (2.5). Fish fed the diet high in PUFA had significantly lower ( P ≤ 0.05) whole body lipid levels and significantly higher ( P ≤ 0.05) protein levels than fish fed the other three diets. These data indicate that the control diet in this study likely contained sufficient lysine, methionine and PUFA to meet the requirements of largemouth bass; however, additional methionine may improve feed conversion efficiency, and increased levels of PUFAs or other factors in squid oil may have a significant impact on body composition.     

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.     

大口黑鲈幼鱼对饲料中锰的需求量

为确定大口黑鲈幼鱼对饲料中锰的需求量,在含锰5.2 mg/kg的半精制饲料中分别添加0、4、8、16、32和64 mg/kg锰(以MnSO₄·H₂O形式),制成6种不同锰水平的饲料(5.2、9.6、13.5、20.7、 38.3和67.9 mg/kg),投喂初始体重(16.00±0.07) g的大口黑鲈幼鱼10周。结果显示,在基础饲料中添加锰,可显著提高大口黑鲈幼鱼的增重率,降低饲料系数,各组增重率与饲料系数在锰含量达到13.5 mg/kg后基本稳定。随饲料中锰含量的增加,血清T-SOD、Mn-SOD活性和全鱼、脊椎骨中的锰含量上升,并在饲料锰含量达到20.7mg/kg后趋于稳定,而血清丙二醛含量则表现为下降的趋势。全鱼铁、骨铁、骨锌和全鱼锰沉积率随饲料锰含量的增加而下降。研究表明,在半精制饲料中补充锰可以促进大口黑鲈幼鱼生长、提高饲料利用率、血清抗氧化能力、全鱼和骨锰的沉积。以增重率、饲料系数、全鱼锰和骨锰为评价指标,经折线回归分析,大口黑鲈幼鱼对饲料中锰的需求量分别为18.3、20.5、21.1和23.4 mg/kg干物质。     

饲料中脂肪与蛋白质比对大口黑鲈生长、体组成和非特异性免疫的影响

为探讨大口黑鲈饲料中不同脂肪与蛋白质含量比对其生长、体组成和非特异性免疫的影响,实验设计了8种(D1~D8)不同脂肪与蛋白质含量比的总能递增饲料。D1~D8饲料的脂肪水平递增(9.0%～26.5%),而蛋白质水平递减(52.0%～31.0%)。用上述饲料饲养体质量为(10.06±0.02)g的大口黑鲈88 d,每饲料设3重复,每重复30尾鱼。结果显示,特定生长率、饲料效率、蛋白质消化率、脂肪消化率和脂肪沉积率均以D2组最高,但随饲料中脂肪与蛋白质含量比的进一步升高呈现显著下降趋势。D3~D5组的蛋白质效率显著高于D1和D8组。D2、D3组与D4组间的蛋白质沉积率差异不显著,但显著高于其他各组。D1~D4组间的总能消化率差异不显著,但显著地高于其他各组。饲料中脂肪含量过高对鱼体组成产生显著的影响,使体脂的积蓄显著增高。随着饲料中脂肪与蛋白质含量比的升高,成活率呈显著下降趋势,D1和D2组的成活率显著高于D5~D8组。非特异性免疫分析显示,D4组血清溶菌酶活力和D2组血清补体活性及头肾白细胞呼吸爆发活性为最高。以饲料为单因子作单因素方差分析得出,满足大口黑鲈最适生长和饲料利用的饲料蛋白质和脂肪水平分别为49.30%和11.50%。以饲料中蛋白质和脂肪水平为自变量,分别以特定生长率和蛋白质沉积率为因变量进行二元二次回归分析得出,特定生长率最大时,饲料中蛋白质、脂肪和脂肪与蛋白质含量比分别为48.20%、12.44%和0.26;蛋白质沉积率最高时,饲料中蛋白质、脂肪和脂肪与蛋白质含量比分别为46.42%、13.96%和0.30。以饲料蛋能比为自变量作一元二次回归分析得出,蛋白质沉积率最大时,饲料的蛋能比、蛋白质、脂肪和脂肪与蛋白质含量比分别为23.72mg/kJ、46.16%、14.18%和0.31。研究认为,饲料的脂肪和蛋白质水平对大口黑鲈的生长、体组成、饲料效率和免疫力有着不同程度的影响;饲料中过高的脂肪会抑制蛋白质的消化与利用,表明脂肪对蛋白质的节约作用有限。建议大口黑鲈实用饲料的蛋白质和脂肪水平分别保持在46%~49%和11.5%~14%范围内较为适当。     

Effects of lipid sources and lipid peroxidation on feed intake, growth, and tissue fatty acid compositions of largemouth bass (Micropterus salmoides)

A 12-week growth trial was conducted to study the effects of replacement of fish oil (FO) with four alternative lipid sources (soybean oil, SO; beef tallow, BT; poultry fat, PF and; palm oil, PO, respectively) on the growth performance, feed intake (FI), and fatty acid (FA) composition in muscle and liver of largemouth bass (Micropterus salmoides) with initial body weight of 6.6 ± 0.01 g. Five isonitrogenous and isoenergetic diets were formulated and added with 5.5 % of each lipid sources, and FO was used as a control group. Until week 8 of the experiment, fish were fed on diets that were conserved at ?20 °C, and fish were fed diets that oxidized at 28–30 °C with natural illumination for 4 weeks during 8–12 week. After 8 weeks of growth trial, specific growth rate and feed conversion of largemouth bass fed BT diet were significantly lower and higher, respectively, than that other dietary treatment (P < 0.05). The fish of PF group had the highest growth performance (P < 0.05). The lipid sources did not affected FI of largemouth bass (P > 0.05). However, growth performance precisely reversed during 8–12 week, and finally, no significant difference was found on growth during 1–12 week. The FA compositions of fish muscle and liver of each treatment reflected the corresponding dietary FA compositions. These results suggested that largemouth bass was sensitive to both of lipid sources and lipid oxidation. Fresh FO, SO, and PF could be optimal lipid sources. Likewise, slightly oxidation of these oils would negatively affected fish growth performance.     

Dietary Protein and Lipid Requirements for Juvenile Largemouth Bass,Micropterus salmoides

A feeding trial was conducted to evaluate dietary protein and lipid requirements for juvenile largemouth bass, Micropterus salmoides. A 4 × 2‐factorial layout included four protein (420, 450, 480, and 510 g/kg) and two lipid (80 and 120 g/kg) levels. Fish (initial weight 8.7 g) were fed the test diets for 8 wk. Weight gain, feed intake, feed conversion ratio, hepatosomatic index, and body composition were dependent on dietary protein level. Nitrogen retention efficiency was independent of dietary protein level, lipid level, and their interaction. Weight gain was higher in fish fed the diet containing 480–510 g/kg crude protein than in fish fed the diet containing 420–450 g/kg crude protein at two dietary lipid levels. The feed intake and weight gain were higher in fish fed the diet containing 484 g/kg crude protein and 115 g/kg crude lipid than in fish fed the diet containing 478 g/kg crude protein and 77 g/kg crude lipid. This study indicated that the suitable dietary protein and lipid levels for largemouth bass are 480–510 g/kg and 120 g/kg, respectively.     

大口黑鲈幼鱼对饲料中锌的需求量

为确定大口黑鲈幼鱼对饲料锌的适宜需求量,以酪蛋白、明胶和鱼粉为主要蛋白质源,以ZnSO_4·H_2O为锌源制作半精制基础饲料,分别向基础饲料中添加0、25、50、100和200 mg/kg锌,制成5种含不同锌水平饲料(24.8、48.8、78.9、126.1和223.6 mg/kg干物质)(命名为Zn-25、Zn-49、Zn-79、Zn-126和Zn-224),投喂初始体质量为(10.99±0.07) g的大口黑鲈幼鱼8周。结果显示,饲料中补充25 mg/kg锌(Zn-49)显著提高了大口黑鲈增重率,降低了饲料系数,进一步提高锌的添加量后,各组增重率和饲料系数趋于稳定。当饲料锌含量为25～49 mg/kg时,T-SOD和CuZn-SOD活性增加,锌含量达到49 mg/kg后,其活性保持基本稳定,而AKP活性在Zn-79组最高。大口黑鲈全鱼和脊椎骨中的锌含量随饲料中锌含量的增加而上升,当饲料锌含量达到126 mg/kg (Zn-126)后,全鱼和脊椎骨中的锌含量不再显著增加,而全鱼铁、骨铁、骨锰含量和全鱼铁、锌沉积率则随饲料锌含量的增加而下降。研究表明,在半精制饲料中补充锌可以显著改善大口黑鲈的生长和饲料利用,提高血清免疫能力、全鱼锌和骨锌的沉积,以增重率、饲料系数、全鱼锌和骨锌为指标,基于折线模型确定大口黑鲈幼鱼对饲料中锌的需求量分别为45.5、44.6、121.8和130.5 mg/kg干物质。     

Effect of protein and lipid dietary levels on the growth of juvenile meagre (Argyrosomus regius)

This study investigates the effects of dietary lipid and protein levels in the growth, feed utilization and body composition of meagre (Argyrosomus regius). Triplicate groups of juvenile fish (23.4 ± 4.9 g average weight ± SD) were fed four isolipidic diets (17.5% crude lipids) containing 40, 45, 50 and 54% of protein, while in a separate experiment, fish (21.8 ± 3.7 g average weight ± SD) were fed four isonitrogenous (50% crude protein, dry matter) each containing 12, 15, 17 or 20% of crude lipids. In the protein requirement experiment, the increase in crude protein in the diet from 40 up to 50% positively affected SGR (Specific growth rate) and FCR (Feed conversion ratio). The increase in crude lipids in the diet from 12 up to 17% showed a tendency for improvement in SGR and FCR. In both experiments, the fastest growing fish exhibited higher lipid depots. Overall, the present investigation showed that juvenile meagre has an estimated protein requirement of 50% and it does not seem to require high dietary lipid levels.     

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.     

Effect of Partial and Total Replacement of Fish Meal on Growth and Body Composition of Sunshine Bass Morone chrysops×M. saxatilis Fed Practical Diets

With the increasing emphasis to replace fish meal (FM) with less expensive protein sources in aquaculture diets without reducing weight gains, an 8-wk feeding trial was conducted with juvenile (15 g) sunshine bass Morone chrysops×M. saxatilis) to evaluate growth and body composition when fed diets with different levels of FM (0, 7.5, 15, and 30%). Six practical floating diets were formulated to contain 40% protein and similar energy levels, with various percentages of FM, meat-and-bone meal (MBM), soybean meal (SBM), poultry by-product meal (PBM), and/or distillers grains with solubles (DGS). Ten fish were stocked into each of 24 110-L aquaria and were fed twice daily ad libitum (0730 and 1600 h). At the conclusion of the feeding trial, final weights of fish fed diet 2 (0% FM, 29% SBM, 29% MBM, and 10% DGS), diet 3 (0% FM, 32% SBM, and 28% PBM), diet 5 (15% FM and 44% SBM), and diet 6 (30% FM and 26% SBM) were not significantly different (P > 0.05) and averaged 72 g. However, final weights of sunshine bass fed diet 1 (0% FM, 30% SBM, and 31% MBM) and diet 4 (7.5% FM and 54% SBM) were significantly lower and averaged 55 g. Specific growth rate (SGR) of sunshine bass fed diet 4 was significantly lower (2.14) than fish fed diet 2 (2.70), diet 3 (2.80), diet 5 (2.68), and diet 6 (2.84), while feed conversion ratio (FCR) of fish fed diet 4 was significantly higher than sunshine bass fed diets 2, 3, 5, and 6. Carcass (fish were decapitated) composition of sunshine bass fed diet 4 had a significantly higher percentage of moisture (70%) and protein (54% on a dry-matter basis) than fish fed all other diets. Percentage lipid was similar among fish fed all diets and averaged 41% (dry-matter basis). Results from the present study indicate that diets in which all of the FM is replaced with a combination of animal- and plant-source proteins can be fed to sunshine bass without adverse effects on weight gain, growth rate, and body composition. Further feeding trials are needed to refine diet formulations used in the present study and should be conducted in aquaria and ponds.     

Replacement of Fishmeal with a Blend of Poultry Byproduct Meal and Soybean Meal in Diets for Largemouth Bass,Micropterus salmoides

A feeding trial was conducted to evaluate the potential of replacing fishmeal with poultry byproduct meal (PBM) and soybean meal in diets for largemouth bass, Micropterus salmoides. A reference diet (C) contained 400 g/kg fishmeal, and 40 or 60% of the fishmeal was replaced with a blend of pet‐food‐grade PBM and soybean meal (diets PP1 and PP2) or a blend of feed‐grade PBM and soybean meal (diets PF1 and PF2). No significant differences were found in weight gain, nitrogen retention efficiency (NRE), condition factor, and body composition among fish fed diets PP1, PP2, PF1, and PF2. Feed intake and feed conversion ratio (FCR) were higher in fish fed diet PF1 than in fish fed diet PP1. No significant differences were found in weight gain, NRE, condition factor, and body composition between fish fed diet C and diets PP1, PP2, PF1, and PF2. The feed intake and FCR were lower in fish fed diet C than in fish fed diets PP2, PF1, and PF2. This study reveals that dietary fishmeal level for largemouth bass could be reduced to 160 g/kg by inclusion of PBM and soybean meal in combination.     

饲料中可消化淀粉对大口黑鲈生长、体组成和非特异性免疫指标的影响

配制6种不同可消化淀粉水平(5.93%、8.71%、11.96%、15.11%、18.16%、21.74%)的等氮和等脂肪的饲料,以试验鱼的生长、饲料效率、体组成、血糖及非特异性免疫和血液学参数作指标,评定大口黑鲈饲料中可消化淀粉的适宜水平。用上述6种饲料饲喂初始体质量(28.36 ± 0.10)g 的大口黑鲈48 d,每饲料设3个重复,每重复35尾鱼。采用表观饱食投喂,每天饲喂2次(8:00和16:00)。结果显示,饲料中可消化淀粉水平为21.74%时,大口黑鲈成活率最低;可消化淀粉水平超过8.71%时,鱼体终末体质量、特定生长率和摄食量均显著下降;但饲料效率和蛋白质效率在可消化淀粉水平为11.96%时达到最高。随着饲料中可消化淀粉水平的升高,饲料的蛋白质消化率差异不显著,但脂肪和淀粉的消化率显著降低;全鱼、肌肉、内脏及肝脏的蛋白质含量均显著降低,而水分含量显著升高,脂肪含量在8.71%组达到最高后又显著降低;肝体比、脏体比、肝糖原及血清谷丙转氨酶和谷草转氨酶的活性均显著升高。饲料中可消化淀粉水平高于11.96%时,试验鱼餐后6至12 h呈现持续的高血糖症状;血清蛋白质含量和血清补体活性在可消化淀粉为8.71%时达到最高;而血清溶菌酶活性和头肾白细胞呼吸爆发活性在11.96%组达到最高。另外,红细胞数和红细胞压积未受到饲料中可消化淀粉水平增高的显著影响,但血红蛋白含量显著降低。综合大口黑鲈的生长、饲料效率、体组成、血糖和非特异性免疫指标得出,大口黑鲈对饲料中可消化淀粉的利用与耐受力有限,饲料中可消化淀粉的适宜水平为8.71% ~ 11.96%。     

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.     

Growth performance, feed intake and morphology of juvenile European catfish, Silurus glanis (L.) fed diets containing different protein and lipid levels

The study was carried out with juvenile European catfish to evaluate the effects of commercial diets on growth, feed utilization and changes of selected morphometric traits of fish. Three diets containing different levels of crude protein and lipid: 37 and 12 %, 45 and 15 %, 45 and 20 %, respectively, were fed to triplicate groups of European catfish for 50 days. The fish were fed continuously (24 h day^?1) by automatic belt feeders for fish with a clock drive. Biometric characteristics of fish included the determination of plasticity traits using modified Pravdin method. Fish growth rate and final body weight were statistically higher in variant 45/20 diet (specific growth rate of 2.6 % day^?1). The intergroup significant differences were recorded for food conversion ratio (FCR) and protein efficiency ratio (PER), during the particular decades of the experiment. For the whole period of the growth test, no significant differences in FCR were observed, but the most favorable values of PER were obtained in variant 37/12. Protein retention in fish body ranged from 18.7 to 21.0 %, and fat retention was significantly more variable, ranged from 87.5 to 121.3 %. Fish survival rate recorded during the growth test was higher in all variants (above 95 %). Statistically significant increases in protein and lipid content were found in fish fed diets 45/15 and 45/20. The tested diets have no effect on changes in fish body proportions. The most effective in juvenile European catfish rearing was diet with 45 % of crude protein and 20 % of lipid.     

Dietary Protein Requirements of Juvenile Black Sea Bass,Centropristis striata

A feeding trial was conducted in a recirculating system to determine the dietary protein requirement for juvenile black sea bass. Six isocaloric diets were formulated to contain varying levels of crude protein (CP) ranging from 36 to 56% (36, 40, 44, 48, 52, and 56%) by substituting a mixture of carbohydrates and lipid for fish meal. The feeding experiment was carried out in 18‐75 L aquaria stocked at a density of 15 juveniles (initial average weight 6.7 g) per tank. Fish were fed test diets in triplicate tanks to apparent satiation twice a day for 8 wk. Whole‐body proximate composition was analyzed after the feeding trial. After the feeding trial, weight gain and specific growth rate of fish fed the 44% CP diet were not significantly different from those fed the 48, 52, and 56% CP diets, but were significantly higher (P < 0.05) than those fed the 36 and 40% CP diets. Feed conversion efficiency and protein efficiency ratio were significantly affected by dietary protein level. The dietary requirement of protein for maximum growth of black sea bass juveniles, estimated using broken‐line regression analysis on weight gain, was 45.3% and maximum weight gain occurred at 52.6% based on polynomial regression analysis.     

Dietary cholesterol and lecithin have limited effects on growth and body composition of hybrid striped bass (Morone chrysops × M. saxatilis)

The effects of cholesterol and lecithin on growth and body composition of juvenile hybrid striped bass ( Morone chrysops  ×  M. saxatilis ) were investigated by feeding juvenile hybrids (initial weight 5.0 g) diets containing cholesterol at either 0 or 1% and lecithin at either 0, 2, 4, or 6% in a 2 × 4 factorial design. Each of the eight diets was fed to fish in triplicate 38-L aquaria maintained as a brackish water recirculating system for 8 weeks. Weight gain, feed efficiency, muscle ratio and hepatosomatic index were not significantly ( P  > 0.05) affected by dietary supplementation of cholesterol or lecithin. Supplementation of the diet with lecithin at 4 and 6% significantly ( P  < 0.05) decreased intraperitoneal fat accumulation regardless of dietary cholesterol level. Neither muscle nor liver lipid levels were significantly altered by dietary supplementation of cholesterol or lecithin although both liver and plasma lipid classes were affected. Dietary cholesterol decreased concentrations of liver and plasma free fatty acids and liver phospholipids while increasing concentrations of liver triglycerides and plasma phospholipids. Dietary lecithin did not consistently affect plasma and liver lipid classes although changes in phospholipid levels approaching significance ( P =0.0502 and P =0.0513, respectively) were observed. Thus it is concluded that dietary supplementation with cholesterol or lecithin had no substantial beneficial effects on growth or body composition of juvenile hybrid striped bass.     

High dietary starch inclusion impairs growth and antioxidant status,and alters liver organization and intestinal microbiota in largemouth bass Micropterus salmoides

Five diets (D1, D2, D3, D4 and D5) containing 0, 50, 100, 150 and 200 g starch per kg diet were formulated to investigate the effects of starch level on largemouth bass, Micropterus salmoides. Fish (initial weight: 22.00 ± 0.02 g) were fed the five diets for 90 days. Results indicated that weight gain, specific growth rate and survival of fish fed higher dietary starch level (200 g/kg) were lower than those of fish fed the lower dietary starch levels (0–50 g/kg). Higher dietary starch levels (150–200 g/kg) have a negative effect on antioxidant ability (total superoxide dismutase: T‐SOD; malonyldialdehyde: MDA; total antioxidant capacity: T‐AOC; glutathione peroxidase: GSH‐Px) and liver health (cellular contents leaked, nucleus deformed, endoplasmic reticulum and golgi body disappeared) of largemouth bass. Lower dietary starch levels (0–50 g/kg) modified intestinal microbiota of largemouth bass represented by increasing the relative abundance of beneficial bacterial such as Bacilli, Lactobacillales and Bacteroidales. These results indicated that dietary starch level above 50 g/kg had a negative effect on growth performance and antioxidant status of largemouth bass. Moreover, high dietary starch levels are potentially associated with negative alterations in liver structure and function, and decrease of beneficial gut microbes.     

A Comparative Study of the Dietary Lysine Requirement of Juvenile Striped bass Morone saxatilis and Sunshine bass M. chrysops x M. saxatilis

Previous reports have indicated there are significant differences in both the dietary lysine requirement and the metabolic rate of striped bass and its hybrids. However, there is very little directly comparative data to confirm these suggestions. A series of experiments was conducted to comparatively assess efficiency of protein and energy retention between striped bass Morone saxatilis and sunshine bass M. chrysops♀×M. saxatilis♂ grown under identical culture conditions. In experiment one, a dose response study was conducted using digestible energy (DE) levels of 3,200 kcal/kg and 3,600 kcal/kg. At each level of DE, six levels of dietary lysine were fed to striped bass and sunshine bass. Ten sunshine bass weighing 3.48 ± 0.08 g or six striped bass weighing 3.23 ± 0.14 g were stocked into 15-L tanks supplied with single-pass flow-through fresh water. After 12 wk on the experimental regime, feed conversion ratios (FCR), weight gain, and % nitrogen (N) retention were determined. Nonlinear regression analysis indicated that the dietary lysine requirement of both bass groups was similar. The dietary lysine requirement was determined to be 2.0 ± 0.08% of dry diet (or 6.0 ± 0.26 g lysine/1,000 kcal DE), and 1.7 ± 0.08% of dry diet (or 4.7 ± 0.22 g lysine/1,000 kcal DE), for the 3,200 and 3,600 kcal DE/kg diets, respectively. A second experiment comparatively assessed growth, metabolism, and energy partitioning between striped bass and sunshine bass. Two diets were formulated to be isonitrogenous and isocaloric with a calculated DE level of 3462 kcal/kg and contained lysine concentrations approximating the published dietary requirements of sunshine bass (low lysine = LL diet) and striped bass (high lysine = HL diet). The diets were fed at an average rate of 2% of body weight/d to 25 juvenile striped bass or hybrid bass held separately in eight 2000-L single-pass flow-through tanks supplied with freshwater. In general, growth performance of sunshine bass was superior to striped bass. Both bass groups performed better when fed the HL diet. Mean FCRs were 1.19 ± 0.12 and 1.94 ± 0.29, respectively, for hybrids and striped bass fed the LL diet (P= 0.066); and 1.17 ± 0.07, and 1-58 ± 0.08, respectively, for hybrids and striped bass fed the HL diet (P = 0.011). Mean % gain/d values were significantly higher (P= 0.001) for hybrids (2.77 ± 0.85) than for striped bass (1-30 ± 0.27) when fed the LL diet. When fed the HL diet, mean % gain/d was significantly higher (P = 0.003) for sunshine bass (2.72 ± 0.83) compared to striped bass (1.51 ± 0.25). Additionally, when fed the HL diet, sunshine bass had significantly higher percent nitrogen (P= 0.006) and energy retention (P= 0.014) when compared to striped bass. These results further document that sunshine bass are more efficient at protein and energy retention compared to striped bass in freshwater.     

Digestibility of plant protein-based diets by largemouth bass Micropterus salmoides

Commercial farming of carnivorous fish demands the reduction of environmental impact of feeds; that requires minimal use of dietary animal protein. This study investigated the digestibility of diets formulated exclusively out of plant protein, added feed attractants, by the carnivore largemouth bass, Micropterus salmoides . Juvenile largemouth bass (14.0 ± 1.0 cm) conditioned to accept artificial, dry feed were confined in polypropylene cages and fed ad libitum in three daily meals, seven experimental diets containing varying levels of vegetable and animal protein sources, added of different feed stimulants. After last daily meal, cages were transferred to cylindrical–conical-bottomed, 200-L aquaria, where faeces were collected by sedimentation into refrigerated containers, preserved and later analysed for chemical composition. Soybean meal can be used as partial substitute of animal protein in diets for largemouth bass; the poultry by-product meal shows as a good option as animal protein source in these rations. Control treatment – 50PP : 50AP – yielded best performances; the need for the use of fish meal in the formulation for carnivorous diets is, at least, questionable. Results of the digestibility trials demonstrated the importance of determining the diet digestibility, if precision in the formulation of least-cost feeds for carnivorous fish is the ultimate goal.     

Effects of Dietary Carbohydrate: Lipid Ratio on Growth and Body Composition of Hybrid Striped Bass

A study was conducted to determine the ability of juvenile hybrid striped bass, Morone crysops ♀× M. saxatilis ♂ , to utilize dietary carbohydrate and lipid for energy. Four semipurified diets containing 35% crude protein were formulated to be isocaloric with various levels of dextrin and menhaden fish oil 50 the carbohydrate: lipid ratio (CHO:L) ranged from 2510 to 42:2.5. Diets were fed in triplicate to groups of hybrid striped bass initially averaging 1.5 g/fish in 38 L aquaria receiving a constant supply of hard (> 180 mg/L as CaCO₃) freshwater for a period of eight weeks. Weight gain, feed and protein efficiencies were similar among all dietary groups. Hepatosomatic index (liver weight × 100/body weight), muscle ratio (whole muscle weight × 100/body weight) and condition factor were also similar, while intraperitoneal fat (IPF) ratio (IPF weight × 100/ body weight) was significantly ( P × 0.05) increased as CHO:L decreased. Proximate composition of muscle did not show any effects of diet. However, dry matter and lipid of whole-body increased significantly as CHO:L decreased; conversely whole-body protein was significantly reduced. Moreover, liver glycogen significantly increased as CHO:L decreased. These data indicate hybrid striped bass are able to efficiently utilize carbohydrate for energy; and dietary lipid, which generally caused increased lipid deposition in various tissues, could be partially replaced with carbohydrate to improve fish quality and productivity.