Role of taurine deficiency in inducing green liver symptom and effect of dietary taurine supplementation in improving growth in juvenile red sea bream <Emphasis Type="Italic">Pagrus major</Emphasis> fed non-fishmeal diets based on soy protein concentrate

This study was conducted to investigate the mechanism of green liver symptom induction and the effect of dietary taurine supplementation on growth performance in juvenile red sea bream fed non-fishmeal diets based on soy protein concentrate (SPC). Juvenile fish (initial BW 72 g) were fed for 20 weeks on SPC diets supplemented with taurine at levels of 0, 1.0, and 2.0%. In the taurine-unsupplemented SPC diet group, specific growth rate (SGR) and feed conversion ratio (FCR) were significantly inferior (P < 0.001), and incidence of green liver was observed in 70% of fish. In this group, hepatopancreatic and plasma taurine concentrations were lowest (P < 0.05), hepatopancreatic content of bile pigments was highest (P < 0.05), and osmotic tolerance of erythrocytes was inferior (P < 0.05) among the dietary treatment groups. Serum osmolality of all treatment groups was at similar levels. These physiological abnormalities as well as SGR and FCR were improved by dietary taurine supplementation. These results indicate that the mechanism for induction of green liver symptom is bile pigment overproduction due to increased hemolysis because erythrocytes become osmotically fragile due to dietary taurine deficiency. Taurine supplementation of SPC diets is essential for maintaining normal physiological condition and growth performance in juvenile red sea bream.     

Taurine Supplementation of All-plant Protein Diets for Rainbow Trout (Oncorhynchus mykiss)

Abstract.— Taurine has been demonstrated to be conditionally indispensable for several carnivorous fish species. Current trends in trout production include decreasing levels of fish-meal content in feeds, along with faster growing strains of fish. Taurine may be a limiting nutrient in support of elevated planes of growth for rainbow trout. A 9-wk feeding trial was conducted using a factorial treatment design with protein source (fish meal or plant) and taurine supplementation (four levels) as the main effects. The fish-meal diet series included 23% herring meal and contained 1.76% total sulfur amino acids (TSAA). The plant diet series did not contain any animal proteins and substituted protein from soy protein concentrate in place of the herring-meal protein and contained 1.5% TSAA. Taurine was supplemented at 0, 5, 10, and 15 g/kg dry diet to each of the diets in the plant series and the fish-meal series of diets. All diets were formulated to contain 43.8% crude protein and 20% lipid with an estimated physiological fuel value of 4.2 kcal/g. Fifteen fish were stocked in each of 24 tanks with a mean initial weight of approximately 26.8 g per fish. The unsupplemented fish-meal diet contained 2 g/kg taurine, and the unsupplemented plant diet had taurine levels below the detection limit of 0.1 g/kg diet. Taurine supplementation improved growth, feed conversion ratios, protein retention efficiencies, and energy retention efficiencies of fish fed the plant protein diets. No effects of taurine supplementation were observed for these response factors in fish fed the fish-meal series diets. This study demonstrates that taurine supplementation may be necessary for rainbow trout fed plant-protein-based feeds.     

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.     

Replacement of fishmeal by soy protein concentrate with taurine supplementation in diets for golden pompano (Trachinotus ovatus)

Two 7‐week feeding trials were conducted to evaluate the capacity of golden pompano (Trachinotus ovatus) to use soy protein concentrate (SPC) as a dietary fish meal substitute. In trial I, fish were fed with a control diet (C) containing 400 g kg^?1 fish meal and other four diets in which the fish meal in diet C was replaced by SPC at 20 (R20), 40 (R40), 60 (R60) and 80% (R80). In trial II, a 3 × 2 design was used, and 40 and 80% of the fish meal in diet C were replaced by SPC, with or without 5 g kg^?1 taurine supplementation (six diets, C + T, R40 + T, R80 + T, C, R40 and R80, were formulated). In trial I, no significant difference was found in the feed intake between feeding treatments. The weight gain and nitrogen retention efficiency (NRE) decreased, whereas the feed conversion ratio (FCR) and phosphorus retention efficiency (PRE) increased, with decreasing dietary levels of fish meal. No significant differences were found in the weight gain, FCR and NRE between fish fed diets C and R20, whereas fish fed diets C and R20 had higher weight gain than those fed diets R40, R60 and R80. In trial II, no significant differences were found in the feed intake, weight gain, FCR, NRE and PRE between fish fed diets C + T and C. No significant differences were found in the feed intake, weight gain and NRE between fish fed diets R40 and R40 + T or between fish fed diets R80 and R80 + T. At the end of trial II, no significant differences were found in the condition factor, hepatosomatic index and body composition between fish fed diets C and C + T, or between fish diets R40 and R40 + T, or between fish fed diets R80 and R80 + T, except that fish fed diet R40 had lower body protein content than that of fish fed diet R40 + T. The present study reveals that taurine supplementation can elevate fish meal replacement level by SPC in the golden pompano diets. Fish meal can be reduced from 400 to 320 g kg^?1, if fish meal is substituted by SPC without taurine supplementation, and can be further reduced to 240 g kg^?1, if fish meal is substituted by SPC with 5 g kg^?1 taurine supplementation.     

饲料中添加生物素对草鱼幼鱼生长、体成分和血清生化指标的影响

在纯化饲料中分别添加生物素0、0.05、0.10、0.20、0.40、0.80、1.60 mg/kg投喂初始质量为(5.92±0.25)g的草鱼(Ctenopharyngodon idellus)幼鱼8周,研究了不同生物素添加量对草鱼幼鱼生长性能、饲料系数、机体营养成分、血清生化指标的影响。试验结果显示:与对照组相比,添加生物素提高了草鱼幼鱼的增重率、特定生长率,降低了饲料系数。添加量为0.40 mg/kg时草鱼幼鱼的特定生长率和增重率最大,饲料系数最低,并与对照组存在显著差异(P<0.05);添加不同水平生物素对草鱼幼鱼全鱼水分、粗蛋白、粗脂肪含量无显著影响,但添加量为0.40 mg/kg时粗蛋白含量最大。0.10 mg/kg组和0.20 mg/kg组的全鱼灰分含量显著高于对照组(P<0.05);添加生物素对血清总蛋白(TP)、血糖(GLU)和总胆固醇(TC)无显著影响,但显著提高了血清甘油三酯(TG)含量,各添加组TG含量均显著高于对照组(P<0.05),1.60 mg/kg添加组的高密度脂蛋白胆固醇(HDL-C)和低密度脂蛋白胆固醇(LDL-C)含量显著高于对照组(P<0.05)。综合本试验结果,草鱼幼鱼饲料中生物素适宜添加量为0.40 mg/kg。     

Necessity of dietary taurine supplementation for preventing green liver symptom and improving growth performance in yearling red sea bream Pagrus major fed nonfishmeal diets based on soy protein concentrate

The necessity of dietary taurine supplementation for preventing green liver symptom and improving growth performance of red sea bream Pagrus major fed nonfishmeal (non-FM) diets was investigated. Yearling red sea bream (initial body weight, 580 g) were fed for 36 weeks on non-FM diets based on soy protein concentrate (SPC) supplemented with taurine at levels of 0%, 0.5%, 1.0%, 1.5%, and 2.0%. Specific growth rate (SGR) and feed conversion ratio (FCR) of fish fed the taurine-unsupplemented SPC diet were markedly inferior. In these fish, incidence of green liver was markedly higher and was accompanied by a decrease of tissue taurine concentration and an increase of hepatopancreatic bile pigment content. The green liver symptom was mainly caused by an increase of hemolysis since the erythrocytes became osmotically fragile due to taurine deficiency. Physiological abnormality and growth performance (SGR and FCR) were markedly improved by taurine supplementation to the SPC diets. These results indicate that dietary taurine supplementation is necessary for yearling red sea bream fed non-FM diet based on SPC to maintain normal physiological condition and growth performance.     

Feeding fermented soybean meal diet supplemented with taurine to yellowtail Seriola quinqueradiata affects growth performance and lipid digestion

Feeding experiment was conducted to determine whether fermentation and taurine supplementation of soybean meal (SBM) fed to yellowtail improve growth performance and lipid digestion. Six diets were formulated and designated as SBM, SBM supplemented with taurine (SBM + T), SBM fermented by Bacillus spp. (FSBM1), SBM fermented by Lactobacillus spp. (FSBM2), FSBM2 supplemented with taurine (FSBM2 + T), and fish meal (FM). Yellowtail fingerlings with an initial body weight of 42 g were stocked in 200‐L tanks. The fish were fed, each diet was fed twice daily in two separate tanks for 8 weeks. Results showed that lipid digestibility of the SBM diet was significantly lower than that of the FM diet, but SBM diet lipid digestibility was improved by taurine supplementation and fermentation. Lipase activity in anterior intestinal digesta, lipid contents in liver and muscle, and bile acid concentrations in gallbladder and anterior intestinal digesta were significantly lower in fish fed SBM diet than in fish fed FM diet; these parameters were not significantly different between fish fed SBM + T, FSBM2, FSBM2 + T diets and FM diet. Although taurine supplementation or fermentation improved lipid digestibility compared with FM diet, growth parameters were only improved in the fish fed FSBM2 + T diet, indicating that apart from a lack of taurine, SBM contains other factors responsible for inferior growth of yellowtail. These factors can be partially eliminated by Lactobacillus spp. fermentation.     

Effect of taurine supplemented practical diet on growth performance and taurine contents in whole body and tissues of juvenile Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

ABSTRACT:   The effect of dietary taurine on juvenile Japanese flounder was determined by feeding three taurine-supplemented experimental diets (TAU) and a commercial diet (CD) to evaluate a practical diet for juvenile Japanese flounder. Juvenile Japanese flounder were reared on the three experimental diets supplemented with taurine at 0, 0.5, 1.0% and CD. These diets were fed to juvenile Japanese flounder of an initial mean body weight of 0.2 g for 6 weeks at 20°C and the taurine contents of the whole body and tissues were analyzed. The final average body weight of juvenile Japanese flounder fed the 1.0% TAU was significantly higher than that of the other groups. Taurine contents in the whole body and tissues increased with the increase in dietary taurine level. These results indicate that juvenile Japanese flounder require at least 15 mg/g taurine in the diet, even though a combined mix of fish, krill and squid meal was the main protein source in the experimental diets.     

Dietary vitamin E requirement of sub‐adult genetically improved farmed tilapia strain of Nile tilapia (Oreochromis niloticus) reared in freshwater

A two‐factor orthogonal test was conducted to determine the dietary vitamin E (VE, dl ‐α‐tocopheryl acetate) requirement for sub‐adult GIFT strain of Nile tilapia (Oreochromis niloticus) at two lipid levels, and evaluate its effect on antioxidant responses. A basal diet containing 60 or 130 g/kg of soybean oil was supplemented with 0, 20, 40, 60, 120 and 240 mg VE/kg, respectively. Each diet was fed to three replicate groups of tilapia with initial weight (80.3 ± 0.7) g for 10 weeks. Results showed that the weight gain, feed efficiency and hepatic VE retention of fish were significantly increased by the increased VE in diets. In groups with 60 and 130 g/kg lipid, fish fed diets supplemented with VE had higher serum superoxide dismutase (SOD) and catalase activity, and lower malondialdehyde content than fish fed the VE un‐supplemented diet (p < .05). The proximate composition of fish had no significant difference in the group with 130 g/kg lipid, whereas crude lipid and ash content were significantly affected by dietary VE in the group with 60 g/kg lipid. Based on broken‐line regression analysis, dietary VE requirement to support the maximum weight gain and serum SOD were 43.2–45.8 and 66.0–76.1 mg/kg in diets with 60 and 130 g/kg lipid, respectively.     

Soy protein concentrate as an alternative in replacement of fish meal in the feeds of hybrid grouper,brown‐marbled grouper (Epinephelus fuscoguttatus) × giant grouper (E. lanceolatus) juvenile

Hybrid grouper juveniles (body weight, 6.1 ± 0.7 g) (brown‐marbled grouper, Epinephelus fuscoguttatus × giant grouper, E. lanceolatus) were fed with six isoproteic (50% crude protein) and isolipidic (12% crude lipid) feeds containing different levels of soy protein concentrate (SPC) in replacement of fish meal (SPC at 20%, 30%, 40%, 50% and 60% protein) and control feed (SPC0) for 6 weeks. Hybrid grouper juveniles were cultured in 100‐L fibreglass tank equipped with flow‐through water system and fed twice a day to apparent satiation level. The highest and lowest growth was recorded in fish fed SPC20 and SPC60 respectively. However, growth of SPC20 was not significantly higher than those fed SPC0, SPC30, SPC40 and SPC50 (p > .05). A decreasing growth trend was observed with the increasing level of SPC from feed SPC40 to SPC60. A noticeable better feed utilization was also observed in fish fed SPC0, SPC20, SPC30, SPC40 and SPC50 compared to fish fed SPC60 (p < .05). The fish condition factor, hepatosomatic index, viscerosomatic index and whole body proximate content of the fish were not affected by the graded levels of SPC. However, the body lipid content was significantly lower in fish fed SPC40 to SPC60 (p < .05). The apparent digestibility coefficient (ADC) of protein and lipid was significantly higher in fish fed SPC0 and SPC20 compared to other dietary treatments (p < .05). Based on the regression analysis on specific growth rate, the study suggests that the hybrid grouper grow best at 21.4% and can utilize up to 50% inclusion level of SPC in protein without significantly affect their growth and its body condition.     

Growth,feed utilization and body composition of Asian catfish (Pangasius hypophthalmus) fed at different dietary protein and lipid levels

This study examined the effect of dietary protein and lipid levels on growth, feed utilization and body composition of Asian catfish Pangasius hypophthalmus reared in cages. Eight test diets were formulated at four protein (340, 380, 420 and 460 g kg⁻¹ crude protein) and two lipid (50 and 90 g kg⁻¹ crude lipid) levels. Fish (initial weight 4.7 g fish⁻¹) were fed the test diets for 8 weeks. Final body weight, weight gain (WG), feed intake (FI), feed conversion ratio (FCR), contents of crude protein, lipid and energy in whole body were dependent on both dietary protein and lipid levels, while specific growth rate (SGR), hepatosomatic index and body moisture content were dependent on dietary lipid level. The WG and SGR increased with the increase in either dietary protein level (at the same lipid level) or lipid level (at the same protein level). The FI and FCR decreased with the increase in dietary protein level (at the same lipid level) or lipid level (at the same protein level). Protein sparing action occurred in case dietary lipid level increased. Fish fed the diet containing 453 g kg⁻¹ crude protein and 86 g kg⁻¹ lipid had the highest WG and SGR, but the lowest FI and FCR, among the diet treatments. There were no significant differences in the protein retention efficiency (PRE) and energy retention efficiency (ERE) among the diet treatments, although PRE and ERE were relatively high in fish fed the diet containing 453 g kg⁻¹ crude protein and 86 g kg⁻¹ lipid. At the end of the feeding trial, body protein content increased, while body lipid content decreased, with the increase in dietary protein content at the same lipid level. Our results suggest that dietary levels of 450 g kg⁻¹ crude protein and 90 g kg⁻¹ lipid are adequate to support fast growth of P. hypophthalmus reared in cages.     

Effects of dietary taurine levels on epidermal thickness and scale loss in red sea bream,Pagrus major

Taurine is often added to artificial fish diets to compensate for a reduction in fish meal (FM). However, the taurine content of FM‐based diets is typically lower than in diets consisting of raw fish, even in diets where FM is the only protein source. We evaluated the effects of dietary taurine in FM‐based diets on epidermal thickness and scale detachability in red sea bream Pagrus major. We compared the effect of diets containing 0% (control), 0.3% (Tau‐0.3%), 0.6% (Tau‐0.6%) and 1.0% (Tau‐1.0%) taurine. Red sea bream (average body weight, 39 g) were fed these diets for 7 weeks. Taurine supplementation had no effect on growth, feed intake, feeding efficiency, or survival. However, the epidermal thickness was higher in fish in the Tau‐0.6% and Tau‐1.0% groups than in the control and Tau‐0.3% groups. Similarly, scale loss was significantly higher in the control group than in the Tau‐0.6% and Tau‐1.0% groups. Our results suggest that supplementation with >0.6% taurine (1.0% in diet) improves skin condition.     

牛磺酸及相关氨基酸对鲈鱼(Lateolabrax japonicus)幼鱼生长及组织氨基酸含量的影响

以平均体重为(8.13±0.05)g的鲈鱼(Lateolabrax japonicus)幼鱼为研究对象,探讨了在低鱼粉饲料中添加牛磺酸、蛋氨酸和半胱氨酸对鲈鱼幼鱼生长及鱼体氨基酸组成的影响.分别在基础饲料中添加0(对照组T-0)、1.0％牛磺酸(T-1)、2.0％牛磺酸(T-2)、0.5％蛋氨酸(M-0.5)和0.5％半胱氨酸(C-0.5)制成5种等氮等脂的实验饲料,在室内流水养殖系统中进行为期70 d的养殖实验.结果显示,T-1、T-2、M-0.5和C-0.5组鲈鱼幼鱼的终末体重、特定生长率(SGR)、增重率(WGR)和摄食率(FI)均显著高于T-0组(P＜0.05);饲料中添加牛磺酸、蛋氨酸和半胱氨酸均可提高鱼体粗蛋白和粗脂肪含量(P＜0.05),鱼体水分含量则呈现出相反的变化趋势;T-I、T-2组肝脏、肌肉中的牛磺酸含量显著高于T-0组(P＜0.05),但M-0.5、C-0.5组肝脏、肌肉中牛磺酸含量与T-0组无显著差异(P＞0.05);T-1、T-2和C-0.5组肝脏的必需氨基酸及总氨基酸含量均高于T-0组(P＜0.05),但M-0.5组肝脏必需氨基酸及总氨基酸含量与T-0组无显著差异(P＞0.05);T-1、T-2、M-0.5和C-0.5组肌肉的必需氨基酸含量均高于T-0组,但只有M-0.5组显著高于T-0组(P＜0.05);T-1、T-2和M-0.5组肌肉的总氨基酸含量高于T-0组(P＜0.05),C-0.5组与T-0组无显著差异(P＞0.05).研究表明,饲料中添加牛磺酸、蛋氨酸和半胱氨酸均可提高鲈鱼幼鱼的生长,同时可以改善鲈鱼肝脏和肌肉中的氨基酸沉积.     

Effect of dietary taurine and cystine on growth performance of juvenile red sea bream Pagrus major

Two experiments were conducted to investigate the effect of dietary taurine and cystine on growth and body composition of juvenile red sea bream Pagrus major. In Experiment I, a casein-based semi-purified diet included a small amount of fish meal were supplemented with taurine at the levels of 0 (control) and 1.0%. The experimental diets in Experiment II were without fishmeal and supplemented with taurine at 0 (control), 0.5, 1.0 and 2.0% or cystine at 1.0 and 2.0%. These diets were fed three times a day for 6 weeks to fish (average body weight: 2.3 g in Experiment I and 2.5 g in Experiment II). In Experiment I, fish fed the taurine-supplemented diet showed significantly (P < 0.05) improved growth, feed efficiency and feed consumption relative to fish fed the unsupplemental diet. The whole body taurine content increased, whereas the non-essential amino acid contents decreased, in fish fed the taurine-supplemental diet compared to fish fed the unsupplemented diet. In Experiment II, the growth, feed efficiency and feed consumption of fish fed the taurine-supplemented diets, irrespective of the dietary taurine levels, were significantly higher than those of fish fed the control diet and the cystine-supplemented diets. Taurine content in the whole body increased with the dietary taurine level, while the taurine contents did not increase by the supplemental cystine. Other free amino acid contents in the taurine-supplemented diet groups followed similar trends to those in Experiment I. These results indicate that supplemental taurine to a casein-based semi-purified diet at more than 0.5% improved the growth and feed performance of juvenile red sea bream. It is also suggested that juvenile red sea bream cannot metabolize cystine into taurine.     

Dietary threonine requirement of juvenile large yellow croaker,Larmichthys crocea

A feeding trial was conducted to determine the dietary threonine requirement of juvenile large yellow croaker (Larmichthys crocea). Six diets were formulated containing 45% crude protein with six graded levels of threonine (0.71–2.46% in about 0.35% increment). Each diet was randomly assigned to triplicate groups of 60 juvenile fish (initial body weight 6.00 ± 0.10 g). Fish were fed twice daily (05:00 and 16:30) to apparent satiation for 8 weeks. The result indicated that significant difference was observed in the weight gain among all treatments. Specific growth rate (SGR), feed efficiency (FE), protein efficiency ratio (PER) and nitrogen retention (NR) increased with increasing levels of threonine up to 1.75% diet (P < 0.05), and thereafter, declined. No significant differences in body dry matter, crude protein, crude lipid or ash content were found among dietary treatments. Theronine contents of fish muscle were significantly affected by dietary threonine levels (P < 0.05). Fish fed the diet with 0.71% threonine showed the lowest threonine content (2.94%) in fish muscle, while fish fed the diet with 1.75% threonine had the highest value (3.16%). Other essential amino acid contents of muscle were not significantly different among the dietary treatments. On the basis of SGR, FE or NR, the optimum dietary threonine requirements of juvenile L. crocea were estimated to be 1.86% of diet (4.13% of dietary protein), 1.90% of diet (4.22% of dietary protein) and 2.06% of diet (4.58% of dietary protein), respectively, using second‐order polynomial regression analysis.     

Effect of 5′‐inosine monophosphate (IMP) and 5′‐guanosine monophosphate (GMP) on the growth,immunity and muscle composition of turbot,Scophthalmus maximus (Linnaeus, 1758)

We evaluated the effect of different concentrations of 5′‐inosine monophosphate (IMP) and 5′‐guanosine monophosphate (GMP) on the growth, immunity and muscle composition of turbot Scophthalmus maximus. Eight diets (containing no IMP or GMP, or 0.5 g/kg IMP, 1.0 g/kg IMP, 2.0 g/kg IMP, 0.5 g/kg GMP, 1.0 g/kg GMP, 2.0 g/kg GMP, or 0.5 g/kg IMP plus 0.5 g/kg GMP) were prepared. A total of 360 fish (average body weight of 105 g) were randomly selected and placed in groups into 24 plastic aquaria (8 treatments × 3 replicates × 15 individuals per plastic aquaria). The tanks were maintained at the temperature of 15 ± 2°C. The experimental diets were fed for 60 days. The specific growth rate (SGR) was significantly higher in S. maximus fed with IMP or GMP compared with fish fed neither IMP nor GMP. The highest SGR was observed in fish fed with 1.0 g/kg IMP. Supplementation with these dietary nucleotides had a positive, but not significant effect on the activity of superoxide dismutase, alkaline phosphatase and acid phosphatase. There was a significant difference in the moisture and crude lipid content of muscle from S. maximus fed the different diets compared with control fish. The highest moisture content was 83.44 for a diet of 0.5 g/kg IMP plus 0.5 g/kg GMP, which was also significantly higher when compared to fish fed alternative diets. The crude lipid content of S. maximus fed diets containing either IMP or GMP was significantly higher than those fed diets without IMP or GMP. Thus, according to these results, the optimal level of dietary IMP is 1.0 g/kg, which correlates with the largest increase in growth performance of S. maximus.     

Dietary lysine requirement of juvenile dusky kob,Argyrosomus japonicus

To determine dietary lysine requirement of dusky kob, Argyrosomus japonicus, six isonitrogenous and isoenergetic diets (431 g/kg crude protein, 141 g/kg lipid and 20 kJ/kg) were formulated with graded levels of crystalline L‐lysine (18–42 g/kg of the dry diet). The protein source in the basal diet comprised fishmeal and soya, where a combination of L‐aspartic and L‐glutamic acids was maintained at a ratio of 1:1, and all diets were supplemented with a mixture of crystalline essential amino acids to simulate the amino acid profile in dusky kob. Dietary treatments were randomly assigned to triplicate groups of 12 fish (4.5 ± 0.2 g, mean weight; 66.5 ± 1.1 mm, total length ± SD), which were fed to apparent satiation three times daily for 12 weeks. The fish fed dietary L‐lysine at 21, 29 and 33 g/kg dry diet showed the highest specific growth rates (SGR) and the lowest feed conversion ratio. For most amino acids, retention in the body of the fish increased with an increase in dietary lysine from 18 to 21 g/kg, and it reached a maximum somewhere between 21 and 33 g/kg, where after amino acid retention decreased with increasing dietary lysine. Based on SGR and using segmented broken‐line analysis, the dietary L‐lysine requirement of juvenile dusky kob was estimated at 31.7 ± 1.6 g/kg dry diet corresponding to 73.5 g lysine per kg protein.     

脱脂亮斑扁角水虻幼虫粉替代鱼粉对黄颡鱼幼鱼生长性能、营养素沉积率、血清生化指标和消化酶活性的影响

为研究脱脂亮斑扁角水虻幼虫粉(DBSFLM)替代鱼粉对黄颡鱼幼鱼生长性能、营养素沉积率、血清生化指标和消化酶活性的影响,本实验选用平均体质量为(1.67±0.01) g的黄颡鱼幼鱼480尾,随机分为4个处理组,分别投喂基础饲料(T0)和实验饲料[脱脂亮斑扁角水虻幼虫粉分别替代鱼粉20%(T20)、40%(T40)和60%(T60)],每个处理组3个重复,每个重复40尾鱼,养殖8周。结果显示,随着DBSFLM替代量的增加,黄颡鱼生长呈先增加后降低的趋势;T20组的终末均重、增重率和特定生长率最高,且显著高于T60组;实验组T20和T60的摄食量显著高于对照组和T40组;实验组的腹脂指数、灰分和钙沉积率呈下降趋势,其中T60组的腹脂指数、T40和T60组的灰分和钙沉积率达到显著水平;与对照组T0相比,实验组的肥满度、脏体比、肝体比、肠体比和胃体比、蛋白质、脂肪和磷沉积率及黄颡鱼体蛋白、体脂肪和灰分均没有显著差异;血清胆固醇和甘油三脂显著降低,高密度/低密度脂蛋白胆固醇显著升高,实验组T40的胃蛋白酶活性有增加趋势、肠道胰蛋白酶活性显著增加。研究表明,在本实验条件下,脱脂亮斑扁角水虻幼虫粉替代鱼粉不影响黄颡鱼幼鱼的生长性能和体组成含量,并可降低腹脂指数、血清甘油三酯、胆固醇含量及灰分、钙的沉积率,还可增加蛋白酶活性,以20%替代比例生长最佳,且优于对照组。     

Comparative study on the effect of dietary lipid level on growth and feed utilization for gibel carp (Carassius auratus gibelio) and Chinese longsnout catfish (Leiocassis longirostris Günther)

An 8‐week growth trial investigated the effect of dietary lipid level on growth performance of a carnivorous fish, Chinese longsnout catfish (Leiocassis longirostris Günther) and an omnivorous fish, gibel carp (Carassius auratus gibelio). For each species, seven isonitrogenous semi‐purified diets (455 g kg^?1 crude protein for Chinese longsnout catfish and 385 g kg^?1 crude protein for gibel carp) were formulated to contain 30, 60, 90, 120, 150, 180 or 210 g kg^?1 lipid. For Chinese longsnout catfish, feed intake (FI) decreased with increasing dietary lipid and there was no significant difference in feed intake from 90 to 210 g kg^?1 lipid. Specific growth rate (SGR) increased with dietary lipid level (P < 0.05) and the 150 and 180 g kg^?1 groups were the best. Feed conversion efficiency (FCE), protein retention efficiency (PRE) and energy retention efficiency (ERE) were higher at 180 g kg^?1 lipid. For gibel carp, FI decreased with increased dietary lipid and 180 and 210 g kg^?1 lipid groups showed lower values. SGR increased with dietary lipid level and the 150 and 180 g kg^?1 were the best. FCE was higher at 180 g kg^?1 lipid level. PRE increased with dietary lipid level and there was no significant difference in groups from 120 to 210 g kg^?1 dietary lipid. ERE increased with increasing dietary lipid level, and groups fed 120, 150 and 180 g kg^?1 lipid showed the highest values. In Chinese longsnout catfish, increase in dietary lipid level, resulted in increased carcass dry matter, crude protein, crude lipid and gross energy. In gibel carp, dry matter, crude protein, and crude lipid increased with dietary lipid level. Based on regression between SGR and dietary lipid, dietary lipid requirements for Chinese longsnout catfish and gibel carp were 142.6 and 140.5 g kg^?1, respectively.     

Taurine is an essential nutrient for yellowtail Seriola quinqueradiata fed non-fish meal diets based on soy protein concentrate

The requirement of dietary taurine in yellowtail fed a non-fish meal (FM) diet based on soy protein concentrate (SPC) was examined by a feeding trial. A recovery test (RCT) was also conducted to confirm the requirement of dietary taurine in yellowtail fed the SPC diet. The non-FM diet including 58% SPC as the protein source was supplemented with 0% (NTS) and 4.5% taurine (TS). A diet including 58% FM was also included as a reference. Juvenile fish (initial BW; 470 g) were fed one type of experimental diet for 39 weeks. The RCT group was fed the taurine un-supplemented SPC (NTS) diet for the first 23 weeks, and then fed the taurine supplemented SPC (TS) diet for 16 weeks. Tissue taurine concentration of the NTS group was significantly lower (P < 0.05) than that of the FM group. Specific growth rate (SGR) and feed conversion ratio (FCR) of the NTS group was significantly inferior compared to the FM group. In the NTS group, green liver syndrome was observed in all the samples. In contrast, tissue taurine concentration of the TS group increased to a similar level to that of the FM group. Compared to the NTS group, SGR and FCR of the TS group were significantly improved (P < 0.05) by taurine supplementation to the SPC diet. Moreover, yellowtail of this group could be reared for a long term without any physiological abnormalities, and their physiological condition and performance were comparable to the fish fed the FM diet. Although the physiological condition and performance of the RCT group was markedly inferior as the NTS group at the 23rd week (wk23) of the feeding trial, the physiological condition and performance of the RCT group markedly improved by the switch of the NTS diet to the TS diet at the end of feeding trial on the 39th week (wk39). These results indicate that yellowtail fed a non-FM diet based on SPC require taurine as an essential nutrient for maintaining normal physiological condition and growth performance.