Effect of dietary lipid source and vitamin E on growth,non‐specific immune response and resistance to Aeromonas hydrophila challenge of Chinese mitten crab Eriocheir sinensis

Six purified diets were formulated to contain three lipid sources, fish oil (FO), linseed oil (LO) and soybean oil (SO), at 6% diet lipid crossing two levels of vitamin E (100 and 300 mg α‐tocopheryl acetate/kg diet) for each lipid source (FO100, FO300, LO100, LO300, SO100, SO300). The juvenile Chinese mitten crab, Eriocheir sinensis, respectively, fed on these diets with four replicates for 6 weeks. The crab weight gain (WG) and specific growth rate (SGR) were significantly affected by dietary lipid sources. No difference was found between the crabs fed two levels of vitamin E, but the WG and SGR were numerically higher in crab fed 300 mg/kg vitamin E than those fed the other level of vitamin E. The lipid source and vitamin E level could affect fatty acid composition in the hepatopancreas. The contents of saturated fatty acids (SAFA) and n‐3HUFA were significantly higher in the crab‐fed fish oil. The highest contents of n‐6PUFA and n‐3PUFA were found in the crab‐fed soybean oil and linseed oil respectively. The contents of SAFA, n‐3HUFA and n‐3PUFA were higher in the 300 mg/kg vitamin E treatment. A lower malondialdehyde (MDA) content and higher phenoloxidase (PO) activity were observed in the crab fed 300 mg/kg vitamin E. The results of this study indicate that the Chinese mitten crab fed the diet with 6% fish oil and 300 mg/kg vitamin E showed better growth, antioxidant capacity and resistance to Aeromonas hydrophila.     

Effect of dietary lipids and vitamin E on growth performance,body composition,anti‐oxidative ability and resistance to Aeromonas hydrophila challenge of juvenile Chinese mitten crab Eriocheir sinensis

Vitamin E supplement is important in protecting lipid oxidation and enhancing immunity of aquatic animals. A 10‐week feeding trial was conducted to evaluate the effect of dietary lipid and vitamin E on juvenile Chinese mitten crab Eriocheir sinensis. The experimental diets included three levels of vitamin E (0, 100 and 300 mg kg^?1) and two levels of lipid (6% and 9%). The 9% lipid diet significantly enhanced the body lipid of crabs compared with the 6% lipid diet. The vitamin E concentration of hepatopancreas increased with the increase in vitamin E in the diets regardless of dietary lipid levels. The hepatopancreas fatty acids, especially polyunsaturated fatty acid and highly unsaturated fatty acid, were significantly enhanced by vitamin E supplement or 9% dietary lipid. Vitamin E supplement significantly increased the total antioxidant capacity, superoxide dismutase, lysozyme and phenoloxidase activities of crabs compared with those fed the diets without vitamin E supplement. The hepatopancreas malondialdehyde of crabs fed 100 mg vitamin E kg^?1 was significantly lower than those fed 0 or 300 mg vitamin E kg^?1. The phenoloxidase activity of crabs fed the 9% lipid diet was significantly higher than those fed 6% lipid, irrespective of vitamin E levels. Vitamin E supplementation increased the bacterial resistance of juvenile crab. This study indicates that dietary lipid and vitamin E supplement do not affect crab growth and survival, but vitatmin E supplement at 100 mg kg^?1 can enhance immunity and antioxidant capacity of crab fed 6% or 9% dietary lipids.     

Growth performance,vitamin E status,and proximate and fatty acid composition of channel catfish, <Emphasis Type="Italic">Ictalurus punctatus</Emphasis>, fed diets containing various levels of fish oil and vitamin E

A study was conducted to determine the effect of increasing dietary levels of fish oil on vitamin E requirement and their effect on growth performance, liver vitamin E status, and tissue proximate and fatty acid compositions of channel catfish. Basal purified diets (42% protein and 3,800 kcal DE/kg) supplemented with 6, 10, and 14% menhaden fish oil were each supplemented with 50, 100, and 200 mg vitamin E/kg (3 × 3 factorial experiment). Each diet was fed to juvenile channel catfish in three random aquaria to apparent satiation twice daily for 12 weeks. Weight gain, feed intake, and feed efficiency ratio were not affected by dietary levels of fish oil, vitamin E, or their interaction. Survival rate at the end of week 12 was significantly lower for fish fed diets containing 14% fish oil, regardless of vitamin E content. Whole-body moisture significantly decreased and lipid increased when dietary lipid levels were increased to 10 or 14%. Dietary vitamin E levels had no effect on body proximate composition. Lipid content of liver was not influenced by dietary levels of fish oil and vitamin E or their interaction. Hepatosomatic index significantly decreased with increasing lipid levels but was not affected by dietary levels of vitamin E. Liver vitamin E increased with increasing dietary vitamin E but decreased with increasing fish oil levels. Fatty acid composition of whole body and liver reflected that of dietary lipid but was not influenced by dietary levels of vitamin E. Whole-body saturates increased, whereas MUFA decreased with increasing dietary levels of fish oil. Liver saturates were not affected by fish oil levels, but MUFA and n-6 decreased and increased, respectively, with increasing fish oil levels. Total n-3 and n-3 HUFA in both tissues increased with increasing fish oil levels in diets, but liver stored much higher levels of these fatty acids.     

Dietary choline improves growth performance,antioxidant ability and reduces lipid metabolites in practical diet for juvenile Pacific white shrimp,Litopenaeus vannamei

An 8‐week feeding trial was conducted to evaluate the effects of dietary choline levels on growth performance, antioxidant capacity and lipid metabolites in juvenile Pacific white shrimp. Six isonitrogenous and isolipidic diets were formulated to supply 0, 1,000, 2,000, 4,000, 6,000, 10,000 mg/kg choline chloride, and dietary choline levels were analysed to be 1,317 (basal diet), 1,721, 2,336, 3,294, 5,421 and 9,495 mg/kg, respectively. Dietary choline levels significantly influenced percent weight gain (PWG) and protein efficiency ratio (PER), with the highest PWG was observed in shrimp fed the 5,421 mg/kg choline diet. However, there were no significant differences in proximate composition of whole body and muscle. Shrimp fed the diet containing 2,336 mg/kg choline had lower HDL and LDL in haemolymph than those fed the basal diet (1,317 mg/kg diet). Dietary choline prevented the accumulation of free radicals and improved antioxidant capacity by increasing catalase activity and reducing malondialdehyde content. Based on broken‐line regression and quadratic regression analysis between PWG against dietary choline levels, the optimal choline requirements were estimated to be 3,254.1 and 6,488.3 mg/kg for juvenile L. vannamei, respectively.     

Optimal dietary lipid requirement of postlarval white shrimp,Litopenaeus vannamei in relation to growth performance,stress tolerance and immune response

A 25‐day experiment was conducted to evaluate the optimal lipid level for postlarval Litopenaeus vannamei. Shrimp (1.7 mg) were fed five isonitrogenous diets containing grade levels of lipid (96.6, 114.3, 128.5, 136.5 and 154.5 g/kg diet, respectively). Each diet was assigned to four tanks (500 shrimp), and shrimp were fed six times a day. Weight gain was increased with the increasing dietary lipid levels, and the highest weight gain was observed in shrimp fed diet with 154.5 g/kg lipid (p < 0.05). On the contrary, the survival was lowest in shrimp fed the L15.45 and highest in shrimp fed the L11.43. Triglyceride in hepatopancreas was increased, and cholesterol was decreased with the increasing dietary lipid. Pyruvate kinase and AMPK mRNA expression were highest in shrimp fed the L12.85. Malondialdehyde in whole body was positively correlated with the dietary lipid levels. The mRNA expression of SOD and Caspase 3 was highest in shrimp fed the L12.85. After hypoxia stress, shrimp fed the L12.85 showed highest survival. The mRNA expression of superoxide dismutase and Akirin was highest in shrimp fed the L11.43 and L15.45, respectively. Based on the survival after 25‐day feeding trail and after the hypoxia stress, the optimal dietary lipid for postlarval L. vannamei should be 118–124 g/kg.     

饲料中不同泛酸水平对凡纳滨对虾生长性能、饲料利用及血清指标的影响

为研究饲料中不同泛酸水平对凡纳滨对虾生长性能、饲料利用及血清指标的影响,实验配制6种等氮等脂(41%粗蛋白质和8%粗脂肪)的实验饲料,泛酸添加水平分别为0(对照组)、50、100、150、300和600 mg/kg,饲料中实测泛酸水平分别为20.9、69.3、99.0、150.2、304.4和513.6 mg/kg。选用初始体质量为(0.73±0.12)g的凡纳滨对虾720尾,随机分为6组(每组3个重复,每个重复40尾),进行为期8周的养殖实验。结果显示,饲料中不同泛酸水平对凡纳滨对虾增重率和特定生长率的影响不显著;对照组凡纳滨对虾成活率显著低于泛酸添加组,然而各泛酸添加组的成活率组间差异不显著。随着泛酸水平从20.9 m.g/kg增加到99.0 mg/kg时,饲料效率和蛋白质效率显著提高,而随着泛酸水平的进一步增加,饲料效率和蛋白质效率显著降低。饲料中泛酸水平对凡纳滨对虾全虾和肌肉主要成分无显著性影响。对照组对虾血清葡萄糖含量显著低于泛酸各添加组,然而泛酸各添加组之间无显著差异;投喂150.2 mg/kg泛酸组血清甘油三酯含量显著低于对照组和513.6 mg/kg;而血清总蛋白和胆固醇含量不受饲料中泛酸水平的影响。随着饲料中泛酸水平由20.9 mg/kg增至150.2 mg/kg,血清超氧化物歧化酶活力显著提高,而随着饲料中泛酸水平的进一步增加,血清超氧化物歧化酶活力显著降低;饲料中泛酸水平为99.0mg/kg组凡纳滨对虾血清总氧化能力显著高于其他各组;投喂对照组和泛酸水平为69.3mg/kg组的凡纳滨对虾血清丙二醛含量最高,投喂泛酸水平为150.2 mg/kg组血清的丙二醛含量显著低于其他各组。以凡纳滨对虾的饲料效率和蛋白质沉积率为评价指标,通过折线模型分析得到凡纳滨对虾泛酸最适需要量分别为113.40和119.87mg/kg。     

实用饲料添加肌醇对草鱼生长、脂质代谢及抗氧化机能的影响

为探讨肌醇对草鱼生长、脂质代谢及抗氧化机能的影响,以实用饲料配方为基础,分别添加0(对照)、50、100、150、200、300和400 mg/kg肌醇,配制成7组等氮等脂的饲料,每组饲料设4个重复,每个重复饲喂初始体质量为(15.00±0.15)g的草鱼25尾,养殖56 d。结果显示,饲料中添加100~150 mg/kg肌醇能显著提高草鱼终末均重(FBW)、增重率(WGR)、特定生长率(SGR)及饲料效率(FE);随饲料肌醇添加水平的上升,全鱼脂肪、肝脏脂肪和脂肪沉积率先升后降,在50~300 mg/kg均与对照组存在显著差异,且均在100 mg/kg达到最大值。肌肉脂肪则逐渐下降并趋于稳定,在100 mg/kg达到最小值,100~400 mg/kg差异不显著;肠脂肪酶、血浆总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)含量及高密度/低密度脂蛋白胆固醇(HDL-C/LDL-C)均呈先升后降的趋势,除LDL-C在各组间差异不显著外,其余指标均在100~150 mg/kg达到最大值;添加肌醇能显著增强肝脏和肌肉中肉碱脂酰转移酶(CPT-I)和乙酰辅酶A羧化酶(ACC)的活性。与对照组相比,100 mg/kg肝脏CPT-I的增幅比例低于ACC的增幅比例,肌肉则相反;当肌醇添加水平为100~150 mg/kg时,肝脏和肌肉中超氧化物歧化酶(SOD)的活性显著升高,丙二醛(MDA)含量及血浆中谷丙转氨酶(ALT)、谷草转氨酶(AST)均显著降低。研究表明,实用饲料添加适宜的肌醇能改善草鱼的生长、饲料转化和肝脏功能,促进脂肪消化,加快脂肪酸的合成与分解代谢,使全鱼和肝脏增脂、肌肉降脂,且能够提高肝脏和肌肉的抗氧化机能。以FE和SGR为效应指标,草鱼实用饲料肌醇适宜添加量为90.3~96.4 mg/kg。     

Effect of dietary vitamin E on growth,immunity and regulation of hepatopancreas nutrition in male oriental river prawn,Macrobrachium nipponense

We evaluated the effects of dietary vitamin E on growth, immunity and regulation of the hepatopancreas in male oriental river prawn, Macrobrachium nipponense. Shrimps were fed 0, 40, 80, 160, 320 or 640 mg vitamin E/kg for 60 days. The 80 mg/kg group had the highest weight gain rate, specific growth rate and lowest feed conversion rate while there were no significant differences in survival rate and hepatosomatic index. The highest crude fat and lowest crude protein content were observed in the 160 mg/kg group. In the hepatopancreas, lysozyme, acid phosphatase and alkaline phosphatase activities were highest in the 160 mg/kg group, while superoxide dismutase, catalase and glutathione peroxidase activities decreased with increasing vitamin E levels. Malondialdehyde content initially decreased then increased with vitamin E levels, whereas the reverse was seen with total antioxidant capacity. Linoleic acid, DPA, DHA, total n‐3 polyunsaturated fatty acid and total polyunsaturated fatty acid first increased then decreased, while EPA and total saturated fatty acid rose with vitamin E levels. Total n‐6 polyunsaturated fatty acid content declined while there were no significant differences in linolenic and total monounsaturated fatty acid content. Following a toxicity test with Aeromonas hydrophila, hepatopancreas ultrastructure revealed that appropriate vitamin E levels promote an increase in mitochondria, endoplasmic reticulum and Golgi bodies, but excess vitamin E can damage cell structure. These results provide evidence that 80–160 mg/kg dietary vitamin E has a positive impact on growth, immunity and regulation of the hepatopancreas in male shrimp.     

维生素E及脂肪源对大菱鲆非特异性免疫的影响

在大菱鲆饲料中分别添加鲤鱼鱼油及花生油作脂肪源,每种脂肪中添加两个水平的维生素E（8mg／kg和300mg／kg维生素E醋酸酯）,饲养大菱鲆84d,探讨其对大菱鲆非特异性免疫的影响。结果发现,（1）以鲤鱼鱼油为脂肪源的添加高剂量的维生素E能提高大菱鲆血清补体活性,而以花生油为脂肪源的饲料添加高剂量的维生素E不影响大菱鲆血清补体活性;（2）以鲤鱼鱼油和花生油为脂肪源的饲料添加高剂量的维生素E不影响大菱鲆中性粒细胞的吞噬率及白细胞总数;（3）以鲤鱼鱼油为脂肪源的饲料添加高剂量的维生素E能提高大菱鲆的溶茵酶活性,但随着时间推移其影响减弱;（4）饲喂n-3HUFA含量高的饲料,对大菱鲆腹水病的抵抗能力高于n-3HUFA含量低的饲料。     

The vitamin E requirement of rainbow trout (Salmo gairdneri) given diets containing polyunsaturated fatty acids derived from fish oil

Groups of rainbow trout (mean initial weight 14 g) were given diets containing 10% of fatty acids derived from a white fish offal oil together with graded levels of vitamin E (2–10 mg/100 g) for 16 weeks. Fish increased in weight by eight-fold over the course of the experiment but there were no differences in weight gain between treatments, food conversion was similar in all treatments, no pathologies were observed and few mortalities occurred. In trout given the lowest dietary vitamin E intake, tissue levels of vitamin E were lowest in skeletal muscle, concentrations in most other soft tissues were about threefold that in muscle but higher levels were found in brain. Increased erythrocyte fragility occurred in those fish given diets low in vitamin E, and ascorbic acid-Fe³⁺-stimulated lipid peroxidation in liver microsomes decreased with increasing dietary vitamin E. Little or no malonaldehyde was formed in microsomes from trout fed diets containing 5 mg vitamin E/100 g or more. This was taken to be an adequate or safe concentration under the dietary conditions employed. Microsomes prepared from the muscle of trout given low levels (2 mg/100 g diet) of vitamin E were more susceptible to peroxidation in vitro than those obtained from gill, heart or liver. Microsomal susceptibility to peroxidation is determined by the ratio of vitamin E: peroxidizable unsaturated fatty acids in the microsomal membrane. Some of these ratios were measured and the results are discussed.     

Effects of dietary vitamin E supplementation on growth performance,fatty acid composition,lipid peroxidation and peroxisome proliferator-activated receptors (PPAR) expressions in juvenile blunt snout bream <Emphasis Type="Italic">Megalobrama amblycephala</Emphasis>

A 9-week feeding experiment was conducted to evaluate the effects of dietary vitamin E (VE) supplementation on growth performance, liver fatty acid composition, lipid peroxidation and peroxisome proliferator-activated receptors (PPAR) genes expressions in blunt snout bream juveniles. Fish (average initial weight: 0.59 g) were fed diet supplemented with 0, 50, 100, 300 and 500 mg α-tocopherol acetate/kg in triplicates, which were found to, respectively, contain 11.2, 56.3, 114.6, 306.5 and 588.4 mg α-tocopherol/kg diet. Results showed that final weight, body weight gain and specific growth rate significantly increased with increasing dietary VE supplemented level from 11.2 to 56.3 mg/kg. When the broken-line model was employed to estimate the adequate requirement of vitamin E based on body weight gain, the optimal level was 55.5 mg/kg in diet. Hepatosomatic index value significantly decreased with incremental dietary VE levels. However, liver VE concentration showed a direct relationship with the dietary VE level. The percentages of 20:5n-3, 22:6n-3 and total n-3 long chain polyunsaturated fatty acids in liver increased with increasing dietary VE supplementation. Meanwhile, the expressions of PPAR-α, PPAR-β and PPAR-γ in liver were down-regulated by supplementation of dietary VE level from 56.3 to 588.4 mg/kg. In conclusion, supplementation of more than 55.5 mg/kg vitamin E may improve growth and increase n-3 LC-PUFA content in blunt snout bream, which is beneficial to human consumer.     

Effects of dietary astaxanthin supplementation on survival,growth and stress resistance in larval and post‐larval kuruma shrimp,Marsupenaeus japonicus

Two trials were conducted to evaluate the effects of chemically synthesized astaxanthin (Ax) on growth performance, survival, and stress resistance in larval and post‐larval kuruma shrimp (Marsupenaeus japonicus). Six dietary levels of Ax (0, 50, 100, 200, 400 and 800 mg/kg diet) were added to a baseline diet. As a first study, an 8‐day feeding trial was conducted on larval kuruma shrimp, with results showing that larvae‐fed diets supplemented with different Ax levels exhibited better performance during developmental and metamorphosis to postlarvae. Broken‐line regression analysis indicated that the optimal levels for growth and stress resistance of larvae were 168.9 mg/kg and 82.1 mg/kg diet, respectively. Second, a 30‐day feeding trial was conducted on post‐larval shrimp. Supplementation with 100 and 200 mg/kg Ax yielded significantly higher final body weight, body weight gain and specific growth rate than that in a control group. A cumulative mortality index for osmotic stress revealed significantly better performance in a group fed 200 mg/kg supplementation than in controls. Broken‐line regression analysis indicated that the optimal levels for growth and stress resistance of postlarvae were 108.7 mg/kg and 178.1 mg/kg diet, respectively. Based on these results, we suggest that carefully dosed Ax supplementation is a beneficial nutritional strategy for the early developmental stages of kuruma shrimp.     

Replacement of fish oil with a DHA‐rich Schizochytrium meal on growth performance,activities of digestive enzyme and fatty acid profile of Pacific white shrimp (Litopenaeus vannamei) larvae

This trial was conducted to evaluate the effects of replacing dietary fish oil with Schizochytrium meal for Pacific white shrimp (Litopenaeus vannamei) larvae (initial body weight 4.21 ± 0.10 mg). Six test microdiets were formulated using Schizochytrium meal to replace 0 g/kg, 250 g/kg, 500 g/kg, 750 g/kg, 1000 g/kg or 1500 g/kg fish oil DHA. No significant differences were observed in survival, growth, final body length and activities of digestive enzyme among shrimp fed different diets (p > .05). No significant differences were observed in C20:5n‐3 (EPA) in muscle samples (p > .05). C18:3n‐3 and C20:4n‐6 in muscle increased as Schizochytrium meal replacement level increased (p < .05). No significant differences were observed in C22:6n‐3 (DHA) and n‐3 fatty acids among shrimp fed diets that algae meal replaced 0 g/kg ‐ 1000 g/kg of fish oil. Shrimp fed diet R150 had higher DHA content than other groups and had higher n‐3 fatty acids than that of shrimp fed diets R50, R75 and R100 (p < .05). C18:2n‐6, PUFA and n‐6 fatty acids in muscle increased, while n‐3/n‐6 ratio decreased with increasing algae meal replacement level from 0 g/kg to 1000 g/kg (p < .05). In conclusion, Schizochytrium meal could replace 1500 g/kg fish oil DHA in the microdiets without negatively affecting shrimp larvae survival, growth and activities of digestive enzyme.     

Effect of dietary oxidized oil and vitamin E on growth performance,lipid peroxidation and fatty acid profile of Labeo rohita fingerlings

A 3 × 3 factorial experiment was conducted on Labeo rohita fingerlings to evaluate the effect of dietary oxidized oil and vitamin E. Nine experimental diets were made, based on three degrees of oil oxidation (fresh oil, low oil oxidation and high oil oxidation), and each level of oxidation was further supplemented with three levels of vitamin E (0, 100 and 1,000 mg/kg). Weight gain% and specific growth rate (SGR) of fish fed fresh fish oil and low oil oxidation level were significantly higher than highly oxidized oil. Moreover, vitamin E supplemented fish also showed better growth performance. Oil oxidation caused a significant reduction in the concentrations of α‐tocopherol and increase in TBARS level and antioxidant enzyme activities in fish liver and muscles. However, increasing the dietary vitamin E abrogated these effects. Dietary vitamin E supplementation improved the fatty acid, more specifically polyunsaturated fatty acids profile of oxidized oil fed fish. In conclusion, dietary oxidized fish oil increased the oxidative stress condition of fish but supplementation of high dose of vitamin E prevented lipid oxidation, improved growth performance and fatty acid profile of L. rohita.     

Effects of α‐lipoic acid on growth performance,body composition,antioxidant profile and lipid metabolism of the GIFT tilapia (Oreochromis niloticus) fed high‐fat diets

The wide use of lipid as a non‐protein energy substitute has led to lipid metabolic problems in cultured tilapia. Therefore, studies that reduce the effects of high‐fat diets in genetically improved farmed tilapia (GIFT) are required. This study evaluated the optimum level and effects of dietary α‐lipoic acid (α‐LA) on growth performance, body composition, antioxidant capacity and lipid metabolism of GIFT tilapia. The basal diet (120 g/kg lipid) was supplemented with six concentrations of α‐LA at 0 (control), L300, L600, L900, L1200 and L2400 mg/kg diet to make the experimental diets, which were fed to GIFT tilapia juveniles (initial body weight: 0.48 ± 0.01 g) for 8 weeks. The weight gain of fish improved significantly in the L300 than other dietary treatments. The intraperitoneal fat index and lipid content of fish fed on the L2400 diet decreased significantly than those fed on the control diet. The activities of superoxide dismutase and glutathione peroxidase (GSH‐Px) in serum and liver were significantly higher in fish fed on the L300 diet than the control. The reduced GSH content of fish fed on the L300 in serum and liver was significantly higher than those fed on control diet. The malondialdehyde content in serum and liver was significantly lower in L300 than in the control. The adipose triglyceride lipase gene was significantly up‐regulated in fish fed on the L2400, but the diacylglycerol acyltransferase 2 gene was down‐regulated in adipose. The liver‐type fatty acid‐binding protein gene in the liver was significantly up‐regulated in fish fed on the L300 and L600 diets. Moreover, the acyl‐coenzyme A oxidase gene in liver was significantly up‐regulated in fish fed on the L300, L600, L900 and L1200 diets. Polynomial regression analysis indicated that 439–528 mg/kg α‐LA is an appropriate dosage in high‐fat diet to improve growth performance and relieve lipid oxidative damage by accelerating lipid catabolism and reducing lipid synthesis in GIFT tilapia.     

Pigmentation of Pacific White Shrimp,Litopenaeus vannamei,by Dietary Astaxanthin Extracted from Haematococcus pluvialis

This study investigated the effectiveness of dietary supplementation of astaxanthin (Ax) from the Haematococcus pluvialis on growth, survival, and pigmentation in Pacific white shrimp. Ten test diets were processed to contain five levels of Ax (25, 50, 75, 100, and 150 mg/kg as fed basis) by adding the natural or synthetic Ax to a basal diet containing no Ax. Each diet and a commercial shrimp feed were fed to four replicate tanks of shrimp (12 shrimp/tank) for 8 wk. Neither the natural nor synthetic Ax affected shrimp growth or survival. After cooking, shrimp fed the diets containing the natural Ax exhibited a strong red color, compared to the light pink color of shrimp fed the remaining diets. Colorimetric readings and Ax content in cooked shrimp demonstrated that the natural esterified Ax had greater pigmentation efficiency than synthetic free Ax (P < 0.05). The Ax contents in shrimp tail muscle demonstrated significant correlation with the levels of dietary Ax. The supplementation level of the natural Ax for optimum pigmentation efficiency is in a range of 75–100 mg/kg diet. The Ax product used in this study contained only a small amount (ca. 5.0%) of other carotenoids, indicating that the high pigmentation efficiency was mainly due to algal esterified Ax.     

Effects of dietary vitamin C and vitamin E on the growth,antioxidant defence and digestive enzyme activities of juvenile discus fish (Symphysodon haraldi)

A 56‐day experiment was carried out to investigate the effects of dietary vitamin C and vitamin E on the growth, antioxidant status and digestive enzyme activities of discus fish (Symphysodon haraldi; initial body weight: 7.96 ± 0.61 g and body length: 5.45 ± 0.65 cm). Animals were fed with 13 different diets including one control diet and 12 treatment diets containing four levels of vitamin C (magnesium‐L‐ascorbyl‐2‐phosphate; 40, 80, 120 and 160 mg/kg) crossed with three levels of vitamin E (DL‐α‐tocopheryl acetate; 40, 80 and 120 mg/kg). The results showed that the fish fed diets containing additional vitamin C (40 mg/kg) and vitamin E (80 mg/kg) showed higher specific growth rate, length growth rate, total antioxidant capacity and protease activity but had lower feed conversion ratio and total superoxide dismutase activity than those fed the control diet. Collectively, these findings suggest that the inclusion of additional 40 mg/kg of vitamin C and 80 mg/kg of vitamin E in the basal diet could have beneficial effect on the growth, antioxidant defence and digestion of S. haraldi.     

Effect of dietary vitamin C on growth performance,body composition and biochemical parameters of juvenile Chu's croaker (Nibea coibor)

Vitamin C is an essential micronutrient for normal physiological and immune functions of fish. However, its requirements and effects in Chu's croaker (Nibea coibor) are currently unknown. A 56‐day feeding trial was conducted to evaluate the optimal dietary vitamin C requirements based on its effects on growth performance, body composition and biochemical parameters in juvenile Chu's croaker (14.17 ± 0.1 g). Six isoproteic (450 g/kg crude protein) and isolipidic (100 g/kg crude lipid) diets were formulated to contain 2.24 (basal diet), 39.03, 85.01, 171.16, 356.49 and 715.46 mg/kg of vitamin C. The results showed that fish fed on 171.16 mg/kg vitamin C diet had the highest growth performance and feed utilization. Fish fed on the basal diet had higher malondialdehyde (MDA) content and lower activities of antioxidant enzymes in the serum and liver as compared with those fed on vitamin C diets. Polynomial analysis indicated that the optimal dietary vitamin C requirements of juvenile Chu's croaker were 102.28, 98.21, 150.26, 165.38, 71.46, 176.19, 84.84 and 103.78 mg/kg based on weight gain, specific growth rate, liver storage, muscle storage, liver MDA content, liver alanine aminotransferase activity, liver alkaline phosphatase activity and liver superoxide dismutase activity, respectively. We recommend an inclusion level in the range of 71.46–150.26 mg/kg vitamin C in the diets of juvenile Chu's croaker for optimum growth performance, liver function, antioxidant capacity and innate immunity functions.     

Canola oil,as a good alternative dietary lipid source in sturgeon: Effects on growth,physiology and fatty acid profile in Beluga sturgeon Huso huso L.

An 8‐week feeding trial was conducted on juvenile beluga sturgeon Huso huso to evaluate the effects of different dietary lipid levels and sources on growth performance, physiological indices, proximate composition and fatty acid (FA) profile. Four practical diets, which had either low level (120 g/kg) of canola oil (LCO) and fish oil (LFO) or high level (240 g/kg) of canola oil (HCO) and fish oil (HFO), were fed to triplicate groups of 25 beluga (mean initial body weight 207 ± 0.5 g). The growth performance of beluga was improved by replacing dietary fish oil with canola oil and increasing dietary lipid level. Except the number of red blood cells, lymphocytes, neutrophils and eosinophils, the rest of haematological factors including the values of haemoglobin, haematocrit, number of white blood cells, mean corpuscular haemoglobin concentration, cholesterol and triglyceride concentrations and the number of basophils and monocytes were not significantly affected by dietary lipid sources or levels. Results showed that both moisture and crude fat of the beluga muscle were affected by dietary lipid. The highest moisture and the lowest fat contents were found in the muscle of beluga fed fish oil (LFO). Moreover, the lowest moisture and the highest fat contents were observed in the muscle of beluga fed canola oil (HCO) (p < .05). The FA profile of the beluga muscle was significantly influenced by dietary treatments. The highest monounsaturated fatty acids, total n‐6 fatty acids containing linoleic acid and arachidonic acid, and total unsaturated fatty acids were found in fish fed canola oil (LCO and/or HCO) (p < .05). However, n‐3 fatty acids containing linolenic acid, eicosapentaenoic acid and docosahexaenoic acid were not affected by the diet (p > .05). FA profile of the beluga muscles reflected the proportions of CO and FO in the diet except that there was a decrease in oleic acid and linolenic acid, but an increase in arachidonic acid (C20:4n‐6), eicosapentaenoic acid and docosahexaenoic acid. The obtained data showed that canola oil is an excellent source of supplemental dietary lipid in a practical fish‐meal‐based diet of beluga sturgeon under the experimental conditions. Moreover, the data demonstrated that increasing dietary lipid up to 240 g/kg in beluga sturgeon resulted to improve growth performance and haematology.     

Effects of dietary vitamin E and astaxanthin on growth,skin colour and antioxidative capacity of large yellow croaker Larimichthys crocea

A 10‐week feeding trial was conducted to evaluate the effect of dietary vitamin E and astaxanthin on growth performance, skin colour and antioxidative capacity of large yellow croaker Larimichthys crocea. Six practical diets were formulated in a 2 × 3 factorial design to supplement with two levels of astaxanthin (25 and 50 mg/kg) and three levels of vitamin E (0, 120 and 800 mg/kg). The results showed that both the highest final body weight and specific growth rate were found in fish fed diets with 120 mg/kg vitamin E supplementation. No significant differences were found in survival rate, feed conversion ratio and protein efficiency ratio among all the treatments (p > .05). Skin lightness (L*) was not significantly affected by dietary treatments (p > .05). Ventral skin redness (a*) of fish fed diet with 25 mg/kg astaxanthin and 0 mg/kg vitamin E supplementation was significantly lower than that of fish fed with other diets. Yellowness (b*) and carotenoid contents both in the dorsal and in the ventral skin were found to be significantly increased with increasing dietary astaxanthin or vitamin E (p < .05), but no significant interactions were found (p > .05). The vitamin E content in liver reflected the dietary vitamin E content. Level of vitamin E content in fish fed diets with 800 mg/kg vitamin E supplementation was significantly higher than that in fish fed with the other diets (p < .05). Liver superoxide dismutase activity and thiobarbituric acid reactive substance levels were found to be decreased with increasing dietary astaxanthin and vitamin E levels, respectively. Levels of reduced glutathione in the liver were found to be increased with increasing dietary vitamin E contents. The total antioxidative capacity in the liver was found to be decreased with increasing dietary vitamin E or astaxanthin contents. In conclusion, adequate dietary vitamin E can improve the growth of large yellow croaker, and the supplementation of astaxanthin and vitamin E benefited the skin coloration and antioxidative capacity of large yellow croaker.