Influence of dietary protein level on growth performance,digestibility and activity of immunity‐related enzymes of leopard coral grouper,Plectropomus leopardus (Lacépède, 1802)

An 8‐week feeding trial was conducted to assess the interaction between dietary protein levels and fish growth, digestibility and activity of immunity‐related enzymes of Plectropomus leopardus. Five diets with different protein levels (400 g/kg, 450 g/kg, 500 g/kg, 550 g/kg and 600 g/kg protein) were designed. P. leopardus fed with 500 g/kg, 550 g/kg and 600 g/kg dietary protein, showed higher weight gain rates than fish fed 400 g/kg and 450 g/kg dietary protein. Ingestion rate in fish fed with 500 g/kg dietary protein was significantly higher than those with other diets. P. leopardus fed with 500 g/kg, 550 g/kg and 600 g/kg dietary protein, showed that feed coefficients were significantly lower than those fed with 400 g/kg and 450 g/kg dietary protein. Net protein utilization was significantly lower in fish fed with 400 g/kg diet than those with other diets. Fish fed with 400 g/kg and 450 g/kg dietary protein had an apparent feed digestibility coefficient for dry matter that was significantly lower than that with other diets. Protease activity was highest in fish fed on 500 g/kg dietary protein. Fish fed with 500 g/kg dietary protein, had the highest superoxide dismutase activity. Fish fed with 600 g/kg dietary protein, had the highest alkaline phosphatase activity. Thus, a diet containing 500 g/kg protein is recommended for P. leopardus aquaculture.     

Effects of ferulic acid on growth performance,immunity and antioxidant status in genetically improved farmed tilapia (Oreochromis niloticus) fed oxidized fish oil

A study was conducted to characterize the effects of dietary oxidized fish oil on the growth performance, immunity and antioxidant status of genetically improved farmed tilapia (Oreochromis niloticus) and to determine the role of ferulic acid on the oxidative damage induced by the oxidized fish oil. The tilapia (13.73 ± 0.31 g) were fed four experimental diets containing untreated (peroxide value, POV: 2.2 meq/kg) and highly oxidized (POV: 120.6 meq/kg) fish oil either with or without ferulic acid (0 or 400 mg/kg) supplementation for 12 weeks. From the results, the oxidized fish oil treatments increased antioxidant enzyme activities and MDA values but decreased the weight gain and the immunological parameters in tilapia. Meanwhile, the serum biochemical indices were significantly affected by the oxidized fish oil. Besides, the addition of ferulic acid partially counteracted the free radical‐induced damage and improved the health status of tilapia. In conclusion, the oxidized fish oil may induce oxidative stress, destroy liver, dysregulate lipid metabolism as well as reduce non‐specific immunity, and eventually result in growth inhibition of tilapia. The ferulic acid supplementation partially offset the negative effects of the oxidized fish oil on tilapia.     

Effects of dietary coated protease on growth performance,feed utilization,nutrient apparent digestibility,intestinal and hepatopancreas structure in juvenile Gibel carp (Carassius auratus gibelio)

This study was conducted to investigate the effects of dietary protease on growth performance, feed utilization, whole‐body proximate composition, nutrient digestibility, intestinal and hepatopancreas structure of juvenile Gibel carp, Carassius auratus gibelio (mean weight 8.08 ± 0.18 g). Six diets were prepared, including a positive control diet (dietary protein 350 g/kg, PC), one negative control diet (dietary protein 33 g/kg, NC) and four protease supplementations diets, which were 75, 150, 300 and 600 mg/kg protease NC diet. After 12 weeks of diet feeding in indoor recycle aquarium tanks, no significant difference (p > .05) was found on growth performance between fish fed diet with 75–600 mg/kg protease and the PC group. Compared with the fish fed the NC diet, the specific growth rate of fish fed 300 mg/kg protease increased significantly (p < .05), as well as protein efficiency ratios (p < .05), while feed conversion was the opposite (p < .05). The nutrient digestibility of crude protein and lipid was higher (p < .05) in fish fed 150 mg/kg protease diet than the PC diet. Whole‐body proximate composition of fish was not affected (p > .05) by the dietary treatment. Serum alkaline phosphatase and albumin were significantly affected by dietary protease (p < .05), while the content of total protein, glucose, triglyceride, total cholesterol, aspartate aminotransferase and alanine aminotransferase activities in serum was not affected (p > .05). Foregut muscular thickness was thinner (p < .05), when the fish fed diets supplementation of protease in 150 or 600 mg/kg diet than the NC diet. Protease activities in hepatopancreas and foregut were higher (p < .05), in the fish fed 150 or 300 mg/kg protease diet than the fish fed the PC diet, but those in the mid‐ and hindgut were not significantly affected (p > .05) by the dietary treatments. Based on the regression analysis of weight gain rate, the optimal dietary inclusion level of protease was 400 mg/kg in the diet for juvenile Carassius auratus gibelio.     

Partial substitution of fish oil with rapeseed, linseed and olive oils in diets for European sea bass (Dicentrarchus labrax L.): effects on flesh fatty acid composition, plasma prostaglandins E2 and F2α, immune function and effectiveness of a fish oil finishing diet

Triplicate groups of European sea bass (Dicentrarchus labrax L.), of initial weight 90 g, were fed four practical‐type diets in which the added oil was 1000 g kg^?1 fish oil (FO) (control diet), 600 g kg^?1 rapeseed oil (RO) and 400 g kg^?1 FO, 600 g kg^?1 linseed oil (LO) and 400 g kg^?1 FO, and 600 g kg^?1 olive oil (OO) and 400 g kg^?1 FO for 34 weeks. After sampling, the remaining fish were switched to the 1000 g kg^?1 FO diet for a further 14 weeks. Fatty acid composition of flesh total lipid was influenced by dietary fatty acid input but specific fatty acids were selectively retained or utilized. There was selective deposition and retention of docosahexaenoic acid (DHA; 22:6n‐3). Eicosapentaenoic acid (EPA; 20:5n‐3) and DHA were significantly reduced and linolenic (LNA; 18:3n‐3), linoleic (LA; 18:2n‐6) and oleic (OA; 18:1n‐9) acids significantly increased in flesh lipids following the inclusion of 600 g kg^?1 RO, LO and OO in the diets. No significant differences were found among different treatments on plasma concentrations of prostaglandin E₂ and prostaglandin F_2α. Evaluation of non‐specific immune function, showed that the number of circulating leucocytes was significantly affected (P < 0.001), as was macrophage respiratory burst activity (P < 0.006) in fish fed vegetable oil diets. Accumulation of large amounts of lipid droplets were observed within the hepatocytes in relation to decreased levels of dietary n‐3 HUFA, although no signs of cellular necrosis was evident. After feeding a FO finishing diet for 14 weeks, DHA and total n‐3 HUFA levels were restored to values in control fish although EPA remained 18% higher in control than in the other treatments. This study suggests that vegetable oils such as RO, LO and OO can potentially be used as partial substitutes for dietary FO in European sea bass culture, during the grow out phase, without compromising growth rates but may alter some immune parameters.     

Juvenile tilapia (Oreochromis niloticus×Oreochromis aureus) requires dietary myo-inositol for maximal growth

An 8-week growth experiment was conducted to estimate the dietary requirement of myo-inositol (MI) for juvenile hybrid tilapia. MI was supplemented at 0, 150, 250, 350, 450, 600, and 1200 mg/kg diet in the basal diet providing 0, 167, 259, 367, 479, 612, and 1253 mg MI/kg diet. Basal diet without MI but with succinylsulfathiazole to suppress MI synthesis by intestinal bacteria was included for comparison. Each diet was fed to triplicate groups of tilapia (mean initial weight 0.51±0.01 g, n=3). Fish fed ≥367 mg MI/kg diet had significantly (P<0.05) higher weight gain, followed by fish fed 259 mg MI/kg diet, and lowest for fish fed the unsupplemented basal diet. Fish fed ≥367 mg MI/kg diet had higher feed efficiency than fish fed the basal diet. Supplementation of dietary inositol did not affect survival of tilapia. The MI concentrations in liver were highest in fish fed the ≥479 mg MI/kg diet, followed by fish fed the 259 and 167 mg MI/kg diets, and lowest in fish fed the basal diet. Hepatic lipid concentrations were higher in fish fed 367 mg MI/kg diet than fish fed ≤259 mg MI/kg diet. Weight gain percentage and MI concentrations in the liver for the different treatments were analyzed by broken-line regression and indicated that the requirement for dietary MI in growing tilapia is about 400 mg/kg diet. Addition of an antibiotic to basal diet did not affect the growth and hepatic inositol concentration of tilapia, suggesting that the intestinal microbial synthesis was not a significant source of inositol for tilapia.     

Influence of Dietary Levels of Magnesium on Growth, Tissue Mineral Content, and Resistance of Channel Catfish Ictalurus punctatus Challenged with Edwardsiella ictaluri

Juvenile channel catfish were fed purified diets supplemented with magnesium (Mg) from Mg sulfate at levels of 0, 200, 400, 600, 800, and 1,000 mg/kg and 0, 200, 400, 600, and 800 mg/kg in two separate feeding studies. In study I, the effect of dietary levels of Mg on growth response, vertebral mineral content, and macrophage chemotaxis were evaluated. Study II had similar objectives except that whole body mineral content was measured, and resistance of channel catfish to Edwardsiella ictaluri challenge was also determined. Fish with an average weight of 10.89 g were stocked at a rate of 50 fish/110‐L aquarium (study I). In study II, fish with an average weight of 4.14 g were stocked at rates of 40 fish/110‐L aquarium. Prior to stocking, each batch of fish was acclimated to laboratory conditions and fed the basal diet for 2 wk. The concentration of Mg in rearing water was 1.8 mg/L. Each diet was fed to fish in quadruplicate and triplicate aquaria to apparent satiation for 10 wk for studies I and II, respectively. Fish fed the basal diet started to die as early as 3 d after the study began (17 d of feeding the diet without Mg supplementation). In both studies, weight gain, survival, and feed efficiency were lowest for fish fed the basal diet but increased with increasing dietary levels of Mg. However, the differences between the values of each of these parameters for fish fed diets containing supplemental Mg were not always significant. Magnesium‐deficiency signs observed were anorexia, sluggishness, convulsions, deformed snout, vertebral curvature, muscle flaccidity, and high mortality. Vertebral and whole body ash concentrations were high, but Mg content was low for fish fed the basal and the 200‐mg Mg diets. Bone Ca content did not differ among fish fed different diets (study I), but whole body Ca tended to increase for fish fed the basal diet, suggesting the possibility of calcification of soft tissues. Macrophage chemotaxis in the presence of exoantigen was highest for fish fed diets supplemented with Mg at 400 and 200 mgkg for studies I and II, respectively. When expressed in terms of chemotaxis index, however, maximum or near maximum value was observed at a dietary Mg level of 400 mg/kg. Thus, a dietary level of Mg of 400 mg/kg from Mg sulfate was required for optimum growth and survival, maintaining high tissue levels of Mg, prevention of muscle flaccidity and skeletal deformity, and stimulating macrophage chemotaxis. Dietary levels of Mg had no effect on the resistance of juvenile channel catfish to Edwarsiella. ictaluri challenge.     

叶黄素对七彩神仙鱼生长和体色的影响

为研究叶黄素对七彩神仙鱼体色和生长的影响,在"牛心汉堡"饲料中分别添加0、50、100、200、300和400 mg/kg叶黄素,饲喂初始平均体质量(10.3±0.3)g的七彩神仙鱼8周。结果显示,添加叶黄素50~200 mg/kg,对鱼体增重率无显著影响,但添加量达200 mg/kg后,饲料系数显著增大,添加量达300 mg/kg后,增重率显著降低。在养殖4周、8周时,鱼体皮肤亮度(L*)无显著变化,皮肤黄度(b*)和叶黄素含量随叶黄素添加量增加而显著升高;8周时,各叶黄素添加组的皮肤b*值和叶黄素含量显著高于4周时,当叶黄素添加量达300 mg/kg后,皮肤b*值(4周、8周)和全鱼叶黄素含量(8周)趋于稳定;4周时,各处理组间的皮肤红度(a*)无显著差异;8周时,当叶黄素添加量达100 mg/kg后,皮肤a*值显著降低;饲料中添加300 mg/kg叶黄素显著提高了七彩神仙鱼肝脏总抗氧化能力。研究表明,在饲料中添加叶黄素可有效改善七彩神仙鱼体表黄色,提高肝脏总抗氧化能力,但高添加量的叶黄素会降低鱼体生长性能,七彩神仙鱼饲料中的叶黄素添加量建议为200~300 mg/kg。     

Effects of dietary bovine lactoferrin on growth,haemato‐biochemical parameters,immune functions and tolerance to air exposure stress in the African cichlid Sciaenochromis fryeri

The effects of dietary bovine lactoferrin (LF) on the growth, haemato‐biochemical parameters, non‐specific serum immunity and stress responses were investigated in the African cichlid, Sciaenochromis fryeri. Four isocaloric diets containing 0 (control), 200, 400 and 800 mg LF kg^?1 diet were formulated and fed to juvenile fish for 8 weeks. The treatments had no effects on the survival rate, growth performance or haematological parameters. Nor were the serum levels of total protein, albumin and globulin significantly influenced. Serum iron levels and total iron binding capacity (TIBC), however, changed vigorously as the result of dietary LF. Dietary LF led to significant reductions in serum levels of alanine transaminase and alkaline phosphatase. The highest lysozyme and bactericidal activities were observed in the fish fed the diets with 200 and 800 mg/kg of LF, respectively, while no changes were observed in their ACH₅₀ levels. Recovery rates were measured after 10 min of air exposure stress. The rate was about twice higher (36% vs 20%) in fish fed on 400 mg LF than in those fed the control diet. Results revealed that adding 400 mg/kg LF could be beneficial as an iron discriminator, for liver function as well as an immune and stress resistance promoter.     

Effects of dietary chlorogenic acid on growth,flesh quality and serum biochemical indices of grass carp (Ctenopharyngodon idella)

The study was to investigate effects of dietary chlorogenic acid (CGA) on growth performance, flesh quality and serum biochemical indices of grass carp (95.1 ± 0.3 g) (Ctenopharyngodon idella) fed seven different diets, including control diet, Eucommia ulmoides (EU)‐supplemented diet (20 g kg^–1) and CGA‐supplemented diets containing 100, 200, 400, 600 and 800 mg/kg CGA. Contents of collagen and alkaline‐insoluble collagen in muscle and skin were significantly increased by dietary CGA and EU (p < .05). Total essential amino acids (TEAA) and total amino acids (TAA) in muscle of grass carp fed EU diet or 400, 600 and 800 mg/kg CGA diet were significantly higher than those of fish fed control diet and 100 and 200 mg/kg CGA diet (p < .05). Fish fed 200–800 mg/kg CGA showed significantly lower muscle crude lipid content than EU, control and 100 mg/kg CGA groups (p < .05). Fish fed CGA‐supplemented diets (100–800 mg/kg) had significantly higher muscle fibre density and lower muscle fibre diameter than control group (p < .05). In conclusion, supplementation of CGA improved flesh quality of grass carp, and supplemental level of CGA for improving flesh quality and growth was estimated to be 400 mg/kg diet.     

Effect of dietary l‐carnitine on growth performance and antioxidant response in Amur minnow (Phoxinus lagowskii Dybowskii)

l ‐carnitine (LC) is required for transporting long‐chain fatty acids into the mitochondria, where β‐oxidation takes place, and it works as an antioxidant molecule against reactive oxygen species. This study evaluated the effects of LC on the growth and antioxidant function of Amur minnow (Phoxinus lagowskii Dybowskii). Five isonitrogenous (380.4 g/kg) and isoenergetic (17.63 MJ/kg) diets were supplemented with five LC levels: control level (0 mg/kg) and treatment levels (50, 400, 750, or 1,100 mg/kg) were fed to fish (18.19 ± 0.56 g) for 120 days. The results showed that the growth performance of fish fed a diet containing 400 mg/kg of LC was significantly higher than that of the control and those fed other LC level treatments. Similarly, the 400 mg/kg treatment had the best feed efficiency. Further, the levels of total antioxidant capacity and total glutathione in the serum and hepatopancreas of fish fed a diet containing 750 mg/kg of LC were significantly increased; however, malondialdehyde levels were significantly reduced compared to those of the control group. The activities of antioxidant enzymes of 750 mg/kg treatments in the serum and hepatopancreas were significantly higher than those of the control group, including total superoxide dismutase, catalase, glutathione peroxidase and gamma‐glutamyl‐cysteine synthetase. Finally, 750 mg/kg treatment significantly upregulated the mRNA relative expression of antioxidant enzymes and nuclear factor erythroid‐2‐related factor 2 and inhibited the mRNA level of kelch‐like ECH‐associated protein 1 in the hepatopancreas. In conclusion, the dietary LC level of 400–750 mg/kg could improve the growth performance, feed utilization and antioxidant defense system of Amur minnow under the culture conditions.     

核苷酸对大黄鱼生长性能、肠道形态和抗氧化能力的影响

为探究饲料中添加核苷酸对大黄鱼生长性能、肠道形态和抗氧化能力的影响,实验选取初始体质量为(7.71±0.02)g的大黄鱼幼鱼为研究对象,设置2个对照组,即高鱼粉对照组FM(鱼粉含量为45.0%)和低鱼粉对照组N0(鱼粉含量为31.5%),在低鱼粉对照组基础上分别添加0、75、150、300、600和1 000 mg/kg的核苷酸,共配制出7种等氮等脂饲料,在海水浮式网箱中进行为期63 d的养殖实验。结果表明:饲料中添加核苷酸对大黄鱼的存活率、饲料效率、摄食率、鱼体组成和形体指标没有显著影响(P0.05);但增重率随着核苷酸添加量的增加呈先升高后下降趋势,在添加量为300~600 mg/kg时显著高于其他处理组(P0.05)。随着核苷酸添加量的增加,血清中超氧化物歧化酶(SOD)和总抗氧化力(T-AOC)的活力呈先升高后下降的趋势,并在300 mg/kg时显著高于低鱼粉对照组(P0.05)。核苷酸对大黄鱼肠道肌肉层厚度和微绒毛高度有显著影响(P0.05),分别在添加量为150和300mg/kg时出现最大值;而对肠道褶皱高度无显著影响(P0.05)。结果表明,饲料中添加核苷酸能促进大黄鱼生长,改善肠道形态结构和增强机体的抗氧化能力。以增重率为指标,利用折线模型计算得到大黄鱼幼鱼饲料中核苷酸的适宜添加量为194.91 mg/kg。     

Substitution effect of sea tangle (ST) (Laminaria japonica) with tunic of sea squirt (SS) (Halocynthia roretzi) in diet on growth and carcass composition of juvenile abalone (Haliotis discus,Reeve 1846)

Substitution effect of sea tangle (ST) with tunic of sea squirt (SS) in diet on growth and carcass composition of juvenile abalone was determined. One thousand four hundred and seventy abalones were distributed into 21 containers. Six formulated diets in triplicate were prepared. A 200 g/kg ST was included into the ST0 diet. The 200, 400, 600, 800 and 1000 g/kg of ST were substituted with the same amount of tunic of SS, referred to as the ST200, ST400, ST600, ST800 and ST1000 diets, respectively. Finally, Undaria was prepared to compare effect of the formulated diets on performance of abalone. The experimental diets were fed to abalone for 16 weeks. Weight gain of abalone fed the ST400 diet was higher than that of abalone fed the ST0, ST600, ST800 and ST1000 diets and Undaria. Weight gain of abalone fed the formulated diets was higher than that of abalone fed the Undaria. The chemical composition of the carcass of abalone was affected by dietary substitution of ST with tunic of SS. In conclusion, ST could be completely substituted with tunic of SS without retardation in performance of abalone. Abalone fed the ST400 diet substituting 400 g/kg ST with tunic of SS achieved the best growth.     

Immunomodulatory Effects of Dietary β‐glucan and Vitamin C in Nile Tilapia,Oreochromis niloticus L., Subjected to Cold‐induced Stress or Bacterial Challenge

To determine the dietary β‐glucan and vitamin C levels that would enable the fish to cope with different stress, 252 tilapia (16.86 ± 0.24 g) were distributed in thirty six 250‐L aquaria and fed experimental diets for 60 d. Diets were supplemented with β‐glucan (0.1, 0.2, 0.4, and 0.8%) and vitamin C (400 and 600 mg/kg diet) and distributed in a factorial design that included a control diet (0 β‐glucan/125 mg vitamin C/kg). After growth performance analyses, a group of 108 fish were subjected to cold‐induced stress and another to Aeromonas hydrophila infection. Hematological and immunological parameters were determined before and after the stress. Growth performance was not affected. Red blood cells, hematocrit, mean corpuscular volume, total plasma protein, albumin : globulin ratio and leukocytes, lymphocytes, neutrophils, and monocytes were affected (P < 0.05) by stress and/or diets. The control diet resulted in higher post‐infection cortisol (P < 0.05). Liver vitamin C was directly proportional to dietary vitamin C (P < 0.05). The production of hydrogen peroxide and nitric oxide was also affected by diets and/or bacterial challenge (P < 0.05). In total, 0.1–0.2% β‐glucan and 600 mg/kg vitamin C increased fish resistance to stress and 0.8% β‐glucan resulted in reduced immune responses regardless of the vitamin C supplementation level.     

饲料中胆碱对大口黑鲈幼鱼生长性能、体成分和血清抗氧化机能的影响

为研究饲料中胆碱对大口黑鲈幼鱼生长性能、体成分以及血清抗氧化机能的影响，在基础饲料中分别添加0 (对照组)、700、1 400、2 100和2 800 mg/kg的氯化胆碱，配制成5组等氮等能的实验饲料(胆碱实测含量分别为2 369.57、2 716.90、2 993.49、3 443.60和3 799.05 mg/kg)，分别投喂初始体质量为(20.00±0.10) g的大口黑鲈幼鱼56 d。结果显示，实验鱼的增重率(WGR)和特定生长率(SGR)随着饲料中氯化胆碱添加量的提高呈先升后降的变化，在添加量为2 100 mg/kg的饲料组均达到最大值，显著高于对照组；饲料中添加氯化胆碱对实验鱼的存活率(SR)、肝体比(HSI)、脏体比(VSI)和肥满度(CF)无显著影响。当氯化胆碱添加量达到2 100 mg/kg饲料及以上时，鱼体肌肉和肝脏的粗脂肪含量均显著低于对照组。相比于对照组，添加1 400～2 800 mg/kg氯化胆碱组的鱼体血清中总抗氧化能力(T-AOC)、超氧化物歧化酶(SOD)活性和过氧化氢酶(CAT)活性显著提高，血清中丙二醛(MDA)的含量显著降低；氯化胆碱添加量为2...     

Use of supplemental amino acids on the success of reducing dietary protein levels for Jian carp (Cyprinus carpio var. Jian)

A feeding trial was conducted to investigate the effects of essential amino acids (EAA) supplementation on the success of dietary protein reduction for Jian carp (Cyprinus carpio var. Jian). Five diets were formulated including a positive control (Diet 1, 378.4 g/kg protein), a negative control (Diet 5, 289.8 g/kg protein) and three test diets (Diet 2‐Diet 4, 340.4–299.0 g/kg protein supplemented with EAA). No significant decline of growth performance in fish fed decreased dietary protein with EAA supplementation, which were significantly higher than the negative control. The apparent digestibility coefficients (ADC) of protein and most EAAs were not significantly affected by the dietary treatments. Dietary treatments did not affect whole‐body composition, but influenced protein and EAAs retentions. Total ammonia nitrogen (TAN) excretion decreased with the decreasing dietary protein, and the highest plasma ammonia content was observed in fish fed Diet 5. Plasma glucose concentration increased with the decreasing dietary protein reduction, while other plasma parameters were not affected by dietary treatments. These results indicated that low‐protein diets (299.0 g/kg) supplemented with EAA can maintain protein, EAA digestibility and retention in Jian carp, and also has benefit in the reduction of TAN excretion.     

不同脂肪源日粮补充维生素E对罗氏沼虾生长、免疫及肉品质的影响

本研究旨在完善罗氏沼虾（）饲料配方,降低罗氏沼虾饲料成本。研究采用3×2双因素设计,配制6组饲料,分别包含鱼油（fish oil,FO）、豆油（soybean oil,SO）、菜籽油（rapeseed oil,RO）三种脂肪源;200 mg/kg（200VE）和600 mg/kg（600VE）两个维生素E（VE）水平。养殖实验在温室水泥池中进行,每个处理3个重复,养殖期8周,每天定点定量投喂3次。结果显示,相对于FO组,SO和RO组增重率、特定生长率显著升高,饵料系数显著下降（>0.05）。对于血淋巴抗氧化指标,在相同VE水平下,FO组血淋巴总抗氧化能力（T-AOC）和超氧化物歧化酶（SOD）活性均显著低于SO和RO组,谷胱甘肽过氧化物酶（GPX）活性均显著高于SO和RO组（<0.05）。在相同脂肪源下,600VE可显著提高FO组T-AOC活性,RO组GPX活性以及SO和RO组SOD活性（>0.05）。对于血淋巴生理生化指标,谷草转氨酶（AST）、总蛋白（TP）、白蛋白（ALB）和甘油三酯（TC）受日粮影响显著（<0.05）。此外,日粮脂肪源和VE水平对肉质也有显著影响。其中,SO组肌肉鲜度和滋味强度较高;RO组鱼腥味较低;FO组肌肉亮度较高,气味强度较低。在200 mg/kg VE水平下,FO组肌肉硬度、胶黏性、耐咀性、黏性和回复性显著高于植物油组（<0.05）,而对肌肉蒸煮损失和滴水损失无显著影响（>0.05）。上述结果表明,相对于鱼油,豆油和菜籽油等植物油是罗氏沼虾更优质的脂肪源,VE在以鱼油为单一脂肪源的饲料中有一定的促生长和缓解应激的作用,且脂肪源和VE均显著影响肌肉品质。本研究结果将为降低鱼油在罗氏沼虾饲料中的使用提供数据支持。     

Effects of dietary orange peel on growth performance,antioxidant activity,intestinal microbiota and liver histology of Gilthead sea bream (Sparus aurata) larvae

This study investigated the effects of dietary orange peel (OP) on growth performance, feed utilization, antioxidant activity, intestinal microbiota and liver histology of Gilthead sea bream (Sparus aurata) larvae (0.32 ± 0.01 g/fish) (mean ± SD). Fish fed iso‐nitrogenous (480 g/kg protein) and iso‐energetic (23 MJ/kg) diets supplemented with OP at concentrations of 0, 1, 3 or 5 g/kg diet, for 60 days. Growth performance and feed utilization parameters were significantly improved by the elevation of dietary OP level, and the optimum level was 5 g/kg diet. The maximum activity of the total antioxidant capacity, superoxide dismutase, glutathione peroxidase, catalase, alkaline phosphatase enzyme and malondialdehyde in the liver was found at 5.5, 4.6, 3.4, 2.9, 3.7 and 3.8 g OP/kg diet, respectively. All tested bacteria (Staphylococcus spp., Vibrio spp. and Salmonela spp) and total bacterial count decreased significantly in the gut of fish fed high levels of OP (3.0 or 5.0 g/kg). No differences were found in the liver histo‐architecture among treatments after 60 days feeding on OP diets. In summary, dietary OP improved growth rate, antioxidant activity and intestinal microbiota of S. aurata larvae with an optimum range from 2.9 to 5.5 g/kg diet.     

军曹鱼幼鱼日粮锌最适添加量的研究

在以卵白蛋白为蛋白源的基础饲料（Zn含量为5．65mg／kg）中添加10、20、30、40、50mg／kg以ZnSO4为Zn源的Zn，使饲料中总Zn含量为15．97、25．66、33．90、45．85、55．88mg／kg。投喂军曹鱼幼鱼8周。试验结果表明，基础饲料组鱼出现生长不良、厌食、皮肤糜烂和白内障等症状，其成活率、增重率、血清碱性磷酸酶活性（AKP）显著低于添加Zn组（P〈0．05），骨骼、肌肉、血清和肝脏Zn含量也表现出相同趋势。10mg／kg和20mg／kgZn添加量组鱼仍出现缺Zn症状，各项测定指标随Zn添加量的增加而增大。当饲料中Zn添加量达到30mg／kg时，各项指标趋向稳定，与添加量40mg／kg和50mg／kg组无显著差异。以增重率和骨骼Zn含量为主要评价指标，通过回归分析表明，以ZnSO4为Zn源时，军曹鱼幼鱼日粮Zn的最适添加量为42．86mg／kg。     

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.     

Ferulic acid: A natural compound as an efficient feed additive for GIFT (Oreochromis niloticus)

This study aimed to investigate the effect of dietary ferulic acid (FA) supplementation on growth performance, antioxidant capacity and some physical characteristics of flesh in genetic improvement of farmed tilapia (GIFT) juveniles. Five diets supplemented with 0, 50, 100, 200 and 400 mg/kg FA were prepared. Weight gain was significantly increased, while feed conversion ratio, viscerosomatic index and hepatosomatic index were significantly decreased in fish fed FA diet at 100 mg/kg feed (p < .05). FA supplementation improved hepatic and serum superoxide dismutase and catalase activities, but decreased the malondialdehyde content (p < .05). Furthermore, with the addition of FA, serum triacylglycerol, cholesterol, low‐density lipoprotein cholesterol contents, alanine aminotransferase and aspartate transaminase activities were reduced, whereas serum high‐density lipoprotein cholesterol content, alkaline phosphatase and lysozyme activities were enhanced. The texture profile analysis parameters and water‐holding capacity tended to increase while cooking loss was decreased by dietary FA supplementation (p < .05). These results suggested that dietary FA supplementation increased the growth performance and antioxidant capacity of GIFT, and improved some physical characteristics of flesh and serum biochemical parameters. The optimum dietary FA level was 100 mg/kg in diet.