Effect of dietary oxidized fish oil on growth performance,body composition,antioxidant defence mechanism and liver histology of juvenile largemouth bass Micropterus salmoides

Four isonitrogenous and isolipidic diets containing fresh fish oil (peroxide value, POV: 11.5 meq kg^?1, diet FR) and three degrees of oxidized fish oil (POV: 132, 277 and 555 meq kg^?1, diet OX₁₃₂, OX₂₇₇ and OX₅₅₅, respectively) were formulated to investigate the effects of dietary oxidized fish oil on growth performance, body composition, antioxidant defence mechanism and liver histology of juvenile largemouth bass. After a 12‐week feeding trail, a proportion of approximately 9% of Micropterus salmoides showed inflammation and haemorrhage at the base of dorsal, pectoral and tail fin in both groups OX₂₇₇ and OX₅₅₅. Fish fed oxidized oil diets obtained significantly higher (P < 0.05) weight gain and specific growth rate because of their remarkable higher feed intakes, compared with the fresh oil receiving group. The analysis of biometric parameters and body composition indicated significant differences (P < 0.05) in various test diets. The activities of hepatic catalase and superoxide dismutase were significantly stimulated (P < 0.05) by oxidized oil ingestion. Hepatic glutathione peroxidase, glutathione reductase and glutathione‐S‐transferase activities were significantly higher (P < 0.05), and liver glutathione content was markedly lower (P < 0.05) in group OX₅₅₅ than the other treatments. Oxidized oil consumption resulted in marked depletion (P < 0.05) of vitamin E concentration in plasma, liver and muscle tissue, increased plasma and muscle malondialdehyde content along with decreased haematocrit value. Histological examinations indicated that hepatocytes with lipid vacuoles and nuclear migration were shown in groups OX₂₇₇ and OX₅₅₅. The overall results in this study suggested that an increased oxidative stress in M. salmoides fed oxidized lipid may account for their stimulated hepatic antioxidant defences, vitamin E depletion in plasma and certain tissues, and pathological changes. The detrimental effect of oxidation products on fish health and the unexpectedly enhanced feed intake of oxidized feeds in M. salmoides underline the importance that cares should be taken to minimize dietary oxidation products to the greatest extent possible.     

Effects of dietary supplementation with coconut oil on the growth,fatty acid profiles and some lipid metabolism relative gene expressions of orange‐spotted grouper Epinephelus coioides

This study investigated the effects of coconut oil as a dietary supplement on the growth, lipid metabolism and related gene expressions of juvenile orange‐spotted grouper Epinephelus coioides. Coconut oil at concentrations of 0, 10, 30 and 50 g/kg was used to replace dietary lipids in a basal diet containing 150 g/kg lipids. The four experimental diets were, respectively, fed to triplicate groups of juvenile groupers (initial weight: 8.53 ± 0.13 g) in a recirculating system for 8 weeks. Fish fed the diet containing 50 g/kg coconut oil exhibited lower (p < .05) weight gain than did fish fed the diet containing 30 g/kg coconut oil; however, no significant differences in weight gain were observed between fish fed diets containing 0 and 10 g/kg coconut oil. Hepatic carnitine palmitoyltransferase‐1, fatty acid synthase, fatty acid elongase, fatty acid desaturase and peroxisome proliferator‐activated receptor gamma gene expressions were all the highest in fish fed the diet containing 10 g/kg coconut oil. Fish fed the coconut oil‐free basal diet demonstrated upregulated gene expression of neuropeptide Y. The results suggest that dietary supplementation with 10 g/kg coconut oil exerted beneficial effects on lipid metabolism by E. coioides.     

Effects of dietary choline on growth performance,lipid deposition and hepatic lipid transport of grouper (Epinephelus coioides)

The number of 360 individuals with an average initial weight of 87.8 ± 0.04 g was fed six diets containing graded levels of choline at 8.1 (control group), 602.5, 1119.0, 1511.5, 1970.0 and 4029.0 mg choline kg^?1 diet, respectively, to investigate the effects of dietary choline on growth performance, lipid deposition and hepatic lipid transport for grouper, Epinephelus coioides. Dietary methionine was estimated to be 10.02 g kg^?1, less than the requirement (13.10 g kg^?1). The results of 10‐week study period indicated that the best values of specific growth rate (SGR), feed conversion rate (FCR) and protein efficiency rate (PER) all occurred in 1119.0 mg choline kg^?1 diet (P < 0.05). The survival range increased from 8.1 to 1511.5 mg choline kg^?1 diet and then plateaued. Dietary choline supplementation significantly decreased the liver lipid content of grouper (P < 0.05), but the lipid content of the muscle tended to be increased firstly and then decreased (P < 0.05). Liver choline concentration reached a plateau in 1511.5 mg choline kg^?1 diet and then levelled off (P < 0.05). Serum high density lipoprotein‐cholesterol (HDL‐C) and total cholesterol (TCHO) levels were firstly decreased and then increased with dietary choline supplementation. A reversed tendency, however, was found in triglyceride. Broken‐line regression analysis of SGR and liver choline content indicated that choline requirement of grouper was 1093.7 and 1579.7 mg kg^?1 diet, respectively.     

Effects of alternative dietary oils on lipid metabolism and related gene expression in hybrid grouper (♀Epinephelus fuscoguttatus × ♂E. lanceolatu)

An 8‐week growth trial was conducted to evaluate effects of dietary oil sources on growth, enzymes activity and genes expression levels related to lipid metabolism of hybrid grouper (♀Epinephelus fuscoguttatus × ♂E. lanceolatu) juveniles. Seven iso‐lipid (97 g/kg of dry matter) and iso‐protein (503.5 g/kg of dry matter) experimental diets were formulated containing 50 g/kg fish oil (FO; acting as controls) or various vegetable oils (VOs): corn oil (CO), sunflower oil (SO), tea oil (TO), olive oil (OO), rice oil (RO) and mixed oil (MO; comprising equal amounts of these oils). Each diet was fed to triplicate groups of 40 fish for per repetition (15.09 ± 0.01 g) for 56 days. The results show that (a) alternative dietary oils had no significant effects on final weight compared with control group (p > .05); (b) compared with FO group, VOs significantly changed the contents of serum lipoproteins, cholesterol, triglycerides and the activity of liver lipid‐metabolizing enzymes (p < .05); (c) CO group had the least effect on the serum lipoproteins, triglycerides and cholesterol of grouper compared with control; the activity of liver lipid‐metabolizing enzymes in RO and control group was the closest; (d) the mRNA levels of Δ6 Fatty acid desaturase (Δ6Fad), hormone‐sensitive lipase (HSL) and lipoprotein lipase (LPL) were not significantly effected by lipid sources, but CO, TO, OO and MO significantly down‐regulated the expression of fatty acid synthetase (FAS) mRNA level in liver, while RO opposite (p < .05); (e) vegetable oil significantly up‐regulated peroxisome proliferator‐activated receptor α (PPARα) and peroxisome proliferator‐activated receptor β (PPARβ) mRNA levels, while TO and RO down‐regulated peroxisome proliferator‐activated receptor γ (PPARγ) mRNA levels (p < .05); and 6) MO significantly increased the mRNA levels of heart‐type fatty acid‐binding protein (H‐FABP) and adipocyte‐type fatty acid‐binding protein (A‐FABP) (p < .05), while other VOs had no effect on them (p > .05). In conclusion, dietary substitution of FO by VO in diet affected lipid metabolism of grouper, which may be regulated by PPARs.     

不同储存条件的鱼油对斜带石斑鱼幼鱼生长性能和抗氧化指标的影响

为研究不同储存时间、温度、抗氧化剂添加量处理的鱼油对斜带石斑鱼生长性能和抗氧化指标的影响,实验鱼油采用如下条件进行氧化处理:储存温度:4℃、环境温度(ambienttemperature,AT):(31.5±3.5)℃;抗氧化剂添加量:30 mg/kg(EQ)、300 mg/kg(HEQ);储存时间:45、90和135 d。根据鱼油储存方式的不同共分为14个处理组,分别为T_(F+EQ)(正对照组,新鲜鱼油+EQ)、T_F(负对照组,新鲜鱼油未加EQ)、T_(4℃+45d+EQ)、T_(4℃+45d+HEQ)、T_(4℃+90d+EQ)、T_(4℃+90d+HEQ)、T_(4℃+135d+EQ)、T_(4℃+135d+HEQ)、T_(AT+45d+EQ)、T_(AT+45d+HEQ)、T_(AT+90d+EQ)、T_(AT+90d+HEQ)、T_(AT+135d+EQ)、T_(AT+135d+HEQ),配制等氮等脂饲料。选择健康幼鱼[初重(18±0.02)g]进行实验,养殖8周。结果显示,T_(4℃+45d+EQ)组增重率与T_(F+EQ)组相比无显著差异,但是显著高于T_(AT+135d+EQ)组。T_(4℃+45d+EQ)、T_(4℃+45d+HEQ)、T_(AT+45d+EQ)和T_(AT+45d+HEQ)组饲料系数较低,与T_(F+EQ)、T_F组比差异不显著,但显著低于T_(AT+135d+EQ)、T_(AT+135d+HEQ)组。T_(F+EQ)、T_(4℃+45d+HEQ)组细胞结构明显,细胞内脂肪粒大小正常,T_(AT+135d+EQ)和T_(AT+135d+HEQ)组鱼油氧化程度较高,肝细胞中脂肪淤积现象明显。T_(4℃+135d+EQ)、T_(AT+135d+EQ)和T_(AT+135d+HEQ)组的CAT活力显著高于T_(F+EQ)、T_F组,SOD和GSHPx均在T_(AT+135d+EQ)组达到最高且显著高于T_(F+EQ)、T_F组。T_(4℃+45d+EQ)、T_(4℃+45d+HEQ)、T_(AT+45d+EQ)和T_(AT+45d+HEQ)组肝脏中MDA含量与T_(F+EQ)、T_F组对比无明显差异,但是显著低于其余各组。研究表明,T_(4℃+45d+EQ)、T_(4℃+45d+HEQ)、T_(AT+45d+EQ)和T_(AT+45d+HEQ)组斜带石斑鱼鱼油生长性能和抗氧化指标相对良好,T_(4℃+45d+EQ)和T_(4℃+45d+HEQ)组更优于T_(AT+45d+EQ)和T_(AT+45d+HEQ)组,说明短期、添加抗氧化剂有利于鱼油的保存,4℃比环境温度保存效果更好。     

Effects of dietary blend of fish oil with corn oil on growth and non-specific immune responses of grouper, Epinephelus malabaricus

A growth trial was conducted to investigate the effects of fish oil and corn oil on the growth and non‐specific immune responses of juvenile grouper, Epinephelus malabaricus. Five semi‐purified diets were supplemented with 40 g kg⁻¹ of either fish oil (F4), corn oil (C4) or blend of fish oil with corn oil at ratio of 3 : 1 (F3C1); 1 : 1 (F2C2) and 1 : 3 (F1C3). Each diet was fed to triplicate groups of grouper (mean initial weight: 10.26 ± 0.14 g) in a recirculating rearing system for 8 weeks. Weight gain and feed efficiency of fish fed the F4, F3C1 and F2C2 diets were the highest (P < 0.05), followed by fish fed the F1C3 diet, and the lowest in fish fed the C4 diet. Fish fed the C4 diet had a lower survival rate than fish on other dietary treatments. Fatty acid composition of liver and muscle in fish generally reflected the composition of the diet. Leukocyte superoxide anion (O⁻₂) production ratio was the highest in fish fed the F3C1 and F2C2 diets, followed by fish fed the F4 and F1C3 diets, and the lowest in fish fed the C4 diet. Fish fed the F3C1 and F2C2 diets had higher plasma lysozyme activities than fish fed the F4 and C4 diets. Plasma alternative complement activity was higher in fish fed the F3C1, F2C2 and F1C3 diets than fish fed the F4 and C4 diets. These results suggest that grouper fed diets with 3 : 1 or 1 : 1 of fish oil to corn oil ratio had similar growth to the fish fed diet with fish oil. Blend of fish oil with corn oil in diet significantly enhanced non‐specific immune responses of grouper when the fed diet contained fish oil as the only lipid source.     

Effects of dietary fish oil replacements with three vegetable oils on growth,fatty acid composition,antioxidant capacity,serum parameters and expression of lipid metabolism related genes in juvenile Onychostoma macrolepis

Five isonitrogenous and isoenergetic diets with soybean oil (SO), linseed oil (LO), algae oil from Schizochytrium sp. (AO), mixed oil (MO, SO:LO:AO = 1:1:1) and fish oil (FO; control group) were selected to feed juvenile Onychostoma macrolepis (initial weight 1.86 ± 0.07 g) for eight weeks. The results showed that in the LO and FO groups fish grew best. There was no significant difference in specific growth rate (SGR) and feed efficiency (FE) between the MO and FO groups (p > .05). The highest contents of 18:2n‐6, 18:3n‐3 and 22:6n‐3 in liver and muscle were found with the SO, LO and AO groups, respectively (p < .05). There appeared the highest malondialdehyde (MDA) content and the lowest superoxide dismutase (SOD) activity in the fish liver of the AO group. There appeared the highest concentrations of serum glucose (GLU), cholesterol (CHOL) and triglycerides (TG) in the SO group. The expressions of lipid anabolism genes were significantly up‐regulated by dietary SO and LO (p < .05). The expressions of lipid catabolism genes were significantly higher with the AO, MO and FO groups (p < .05). This study recommended that LO or MO as a better vegetable oil source for juvenile O. macrolepis.     

Effects of dietary fish oil substitution with linseed oil on growth,muscle fatty acid and metabolism of tilapia (Oreochromis niloticus)

This study was conducted to evaluate the effect of linseed oil (LO) replacing different levels of fish oil (FO) on growth, muscle fatty acid composition and metabolism of gift tilapia (Oreochromis niloticus) (mean initial weight 22 ± 0.5 g) in indoor recycle aquarium tanks for 8 weeks. Fish fed the diet with 50% of the oil as LO had higher final body weight (FWG), specific growth rate (SGR) and protein efficiency ratio (PER) than the other groups (P < 0.05). Hepatopancreas lipid content of fish fed 50% LO was lower than the other groups. Total n‐3 and n‐6 PUFA contents in the dorsal muscle and superoxide dismutase (SOD) activity in serum increased with increasing dietary LO level. Fish fed 50% LO had higher alanine transaminase (ALT), aspartate transaminase (AST) and lipoprotein lipase (LPL) activities in hepatopancreas and total antioxidant capacity (T‐AOC) and alkaline phosphatase (AKP) activities in serum than the other groups (P < 0.05). However, malate dehydrogenase (MDH) activities and malondialdehyde (MDA) contents in hepatopancreas were lower than other groups (P < 0.05) with a 50% substitution level. Results of this study indicated that LO could substitute <50% FO without influencing the growth of tilapia. The higher substitution levels of LO induced negative influences on growth, feed utilization and antioxidant ability of tilapia, but could promote DHA synthesis in tilapia muscle.     

Effects of dietary docosahexaenoic acid sources,microalgae meal and oil,on growth,fatty acid composition and docosahexaenoic acid retention of orange‐spotted grouper,Epinephelus coioides

This study evaluated the effects of Aurantiochytrium spp. microalgae meal and oil as dietary docosahexaenoic acid (DHA) sources on the growth, fatty acid composition and DHA retention of orange‐spotted grouper, Epinephelus coioides. Dietary fish oil was replaced with microalgae meal or oil to provide an equal amount of DHA as a fish oil‐containing basal diet. In total, three experimental diets were fed to triplicate groups of fish (initial wt: 8.48 ± 0.06 g) in a recirculating system for 8 weeks. The weight gain and feed efficiency of the fish did not differ significantly among the experimental diets. The fatty acid composition of the whole body of the fish generally reflected the composition of their diet. The concentration of eicosapentaenoic acid in the whole body was higher in the fish fed the fish meal control diet than in those fed the two experimental diets The fish fed the control diet and those fed the diet containing microalgae oil exhibited higher DHA concentrations than did the fish fed the diet containing microalgae meal. The whole‐body DHA retention was the highest in the fish fed the diet with microalgae oil, followed by the fish fed the control diet. The lowest whole‐body DHA retention was observed in the fish fed the diet containing microalgae meal. The results suggested that the oil from Aurantiochytrium spp. microalgae can be used as DHA source for the grouper. DHA utilization by the fish was higher when the diet was supplemented with microalgae oil than with dry microalgae meal.     

Effect of dietary L‐carnitine supplementation on growth performance and lipid metabolism in Rhynchocypris lagowski Dybowski fed oxidized fish oil

Lipid content of a diet is very susceptible to oxidation, which has many negative effects on farmed animals. Therefore, this study studied the protective effect of L‐carnitine (LC) on fish body stimulated by oxidized fish oil (OFO) from lipid metabolism. Lipid content of the diet was replaced by OFO in 0, 100 and 400 meq/kg. L‐carnitine was added to the diet in two levels, 500 and 1,000 mg/kg, giving a total of seven experimental diets. A total of 735 healthy Rhynchocypris lagowski Dybowski with an initial weight of 4.48 ± 0.14 g after 2‐week adaptation randomly divided into 15 glass aquariums. Fish were fed satiated three times daily. After 8 weeks, biometry was done to evaluate growth performance, and hepatopancreas and muscle samples were taken for biochemical analysis. The result showed that feeding with OFO had negative growth. However, in fish received both OFO and LC, growth indices improved slightly (p > .05). Feeding with OFO and LC, the content of EPA, DHA and PUFA in the muscle of R. lagowski was significantly higher than that in the control group (p < .05), which reached the maximum value in the OFO100 + LC500 group. The content of SFA, MUFA, ∑n‐6 and PUFA in hepatopancreas increased significantly (p < .05), and the content of SFA reached the maximum in OFO100 + LC500 group. Feeding with OFO increased hepatopancreas total cholesterol, triacylglycerol, HDL/LDL ratio, FAS and ACCα that involved in lipid synthesis enzymes, while reduced HL and HSLα enzyme activity and gene expression that associated with lipid decomposition. Dietary LC moderated the effects of OFO on lipid metabolism. According to the result of the present study, it can be argued that feeding of R. lagowski with OFO has negative effects on growth performance and lipid metabolism, whereas LC dosages used in this study have increased the oxidation rate of fatty acids in the hepatopancreas of R. lagowski and improved the accumulation of fat in hepatopancreas cells induced by oxidized fish oil.     

Effects of fishmeal replacement by Tenebrio molitor meal on growth performance,antioxidant enzyme activities and disease resistance of the juvenile pearl gentian grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀)

A 50‐day feeding trial was conducted for juvenile pearl gentian grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀) to determine the optimal amount of Tenebrio molitor meal (TM) that could replace fishmeal (FM) in feeds without reducing growth performance, antioxidant enzyme activities and resistance. Six isonitrogenous and isolipidic diets were formulated with TM replacing 0% (T0), 6.25% (T6), 12.5% (T12), 18.75% (T18), 25% (T25), 31.25% (T31) FM respectively. Each diet was randomly divided into triplicate groups with 30 juveniles (initial weight 6.60 ± 0.00 g). After feeding trail, fish were challenged by Vibrio harveyi for 7 days. The results showed that each treatment had better survival rate between 96.67% and 100%. Fish fed with control and T6 diet showed lower final weight and weight gain rate as compared to other diets. The feed conversion ratio of fish fed on T12 and T18 diet had no significant difference compared to control diet. As compared to control diet, other diets had no significant differences on specific growth rate and temperature growth coefficient. Fish fed with T6 diet had highest liver glutathione reductase activities. No significant differences were observed in liver superoxide dismutase activities in fish fed with T6, T12, T25, T31 and control diet. Fish fed on T18 diet had lowest hepatic malondialdehyde contents and a highest relative per cent survival. According to a broken‐line model, the recommended substituted ratio of TM for FM was estimated to be 12.3% for grouper obtaining maximum WGR, corresponding to additive amount of TM is 4.92%.     

Effects of salinity, aeration and light intensity on oil globule absorption, feeding incidence, growth and survival of early-stage grouper Epinephelus coioides larvae

ABSTRACT: A series of experiments were conducted to examine the effects of salinity, aeration and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage Epinephelus coioides larvae. Newly hatched larvae were transferred to 40-L aquaria at a density of 1500 individuals/aquarium. Larvae were exposed to different levels of aeration (0 mL/min per L, 0.62 mL/min per L, 1.25 mL/min per L, 2.50 mL/min per L, or 3.75 mL/min per L); salinity (8 ppt, 16 ppt, 24 ppt, 32 ppt, or 40 ppt); and light intensity (0 lx, 120 lx, 230 lx, 500 lx, or 700 lx) for 4–6 days. Twenty larvae were sampled daily at 11:00 hours to measure for total length (TL), oil globule volume, and feeding incidence. Survival rates were determined by counting the total number of larvae remaining in each aquarium at the end of the experiment. Significantly higher survival rates ( P   <  0.05) were observed at aeration levels of 0.62 mL/min per L and 1.25 mL/min per L, at salinity levels of 16 ppt and 24 ppt, and at light intensities of 500 lx and 700 lx. The influence of aeration level, salinity and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage grouper larvae are discussed.     

Effects of dietary levan on growth performance,nonspecific immunity,pathogen resistance and body composition of orange‐spotted grouper (Epinephelus coioides H.)

This study investigated the effects of levan produced by Bacillus licheniformis FRI MY‐55 on growth performance, intestinal count of viable bacteria, immune status, pathogen resistance and body composition of orange‐spotted grouper (Epinephelus coioides). Orange‐spotted grouper were fed diets supplemented with levan at concentrations of 0 (control), 5.0, 10.0, 25.0 and 50.0 g kg^?1 for 12 weeks. The final weight and per cent weight gain were significantly higher in the 25.0 g kg^?1 levan‐supplemented group than in the control group (p < 0.05). All levan‐supplemented diets significantly decreased the count of total viable aerobic bacteria and Vibrio spp. in the intestines of groupers (p < 0.05). Serum total protein levels, globulin levels, lysozyme activity and survival rate of orange‐spotted grouper after challenge with V. harveyi were significantly higher in the 25.0 g kg^?1 levan‐supplemented group than in the control group (p < 0.05). This study also found that the 10.0, 25.0 and 50.0 g kg^?1 levan‐supplemented diets significantly increased the crude protein level in the body composition of orange‐spotted grouper. Overall, the results of this study indicate that dietary levan (25.0 g kg^?1) could be an effective method for enhancing the growth performance and disease resistance in orange‐spotted grouper.     

Effect of dietary iron supplement on growth, haematology and microelements of juvenile grouper, Epinephelus coioides

An experiment was conducted to investigate the effect of dietary iron supplement on growth, haematology and microelements of juvenile grouper, Epinephelus coioides. Casein–gelatine‐based diets supplemented with 0, 50, 100, 150, 200 and 250 mg kg⁻¹ iron from ferrous sulphate were fed to grouper (mean initial weight: 21.0 ± 0.2 g) for 8 weeks. Weight gain was highest in fish fed the diet supplemented with 100 mg kg⁻¹ iron, intermediate in fish fed diets with 50, 150, 200 and 250 mg kg⁻¹ iron and lowest in fish fed the basal diet. Feed efficiency followed a similar trend except that the lowest value was in fish fed the basal diet and the diet supplemented with 250 mg kg⁻¹ iron. Hepatic iron was highest in fish fed diets supplemented with iron ≥100 mg kg⁻¹, followed by fish fed diet with 50 mg kg⁻¹ iron and lowest in fish fed the basal diet. The whole‐body iron was lowest in fish fed the basal diet but not significantly different from other groups, as judged by anova . Iron supplement to the basal diet had no significant effect on haematological parameters (red blood cell count, haematocrit and haemoglobin), hepatic copper concentration or manganese, zinc concentration in liver and whole body. Broken‐line analysis of hepatic iron indicated that iron supplementation of 100 mg kg⁻¹ satisfied the hepatic iron storage and that further supplementation did not expand the iron status.     

Effects of dietary fish oil replacement with blended vegetable oils on growth,lipid metabolism and antioxidant capacity of subadult swimming crab Portunus trituberculatus

A 120‐day trial was conducted to assess the effects of dietary fish oil replacement with vegetable oils on growth, lipid metabolism and antioxidant capacity of subadult swimming crab Portunus trituberculatus. Five isonitrogenous and isolipidic diets were formulated to replace 0, 250, 500, 750 and 1000g/kg of fish oil with a mixture of soybean and rapeseed oil (defined as D1–D5), and each treatment had 30 replicate crabs. Dietary fish oil replacement had no significant effects on growth of the crabs, while the D3 had the highest hepatosomatic index and total lipids in hepatopancreas. The triglyceride and lipase activities in hepatopancreas increased significantly with increasing dietary fish oil replacement. The D4 had the highest levels of alkaline phosphatase (ALP) and acid phosphatase (ACP) in the hepatopancreas, as well as the haemolymph ALP, ACP and peroxidase. The highest levels of haemolymph total antioxidant capacity, catalase and malondialdehyde were detected in D1. Total n‐3 polyunsaturated fatty acids levels in hepatopancreas decreased significantly with increasing dietary fish oil replacement. In conclusion, dietary fish oil replacement had no significant effects on growth of P. trituberculatus, and 500g/kg of fish oil replacement could improve antioxidant capacity, but excessive replacement level will enhance lipid accumulation and peroxidation in the hepatopancreas.     

饲料中添加氧化鱼油对黑鲷幼鱼生长的影响

研究了饲料中添加氧化鱼油对黑鲷（Acanthopagrus schlegeli）生长性能、脂质过氧化及肝组织结构的影响。分别以新鲜鱼油（过氧化物值POV，1．27meq O2·kg^-1油）与氧化酸败鱼油（POV，45meq O2·kg^-油）为脂肪源配制等蛋等能的两种配合饲料，投喂平均体重18．9g的黑鲷幼鱼9周。结果显示，氧化鱼油显著降低了黑鲷幼鱼的增重率（WG）、饲料效率（FE）及蛋白质效率（PER）（P〈0．05）。饲料中添加氧化鱼油导致鱼体蛋白质含量极显著降低（P〈0．01）、肝脏与肌肉中脂肪含量显著升高（P〈0．05），而对鱼体、肝脏及肌肉中的水分及灰分含量无显著影响（P〉0．05）。氧化鱼油组肝脏中脂质过氧化产物丙二醛（MDA）含量显著高于对照组，而维生素E含量则显著低于对照组（P〈0．05）。饲料中添加氧化鱼油显著影响黑鲷肝脏内主要抗氧化酶活性，氧化鱼油组肝脏中超氧化物歧化酶（SOD）与过氧化氢酶（CAT）活性显著高于对照组（P〈0．05）；组织学结果显示氧化鱼油组肝脏出现明显病变，细胞核多集中在肝细胞边缘，肝细胞变大。统计分析表明，氧化酸败油脂显著降低了黑鲷的生长性能，加重了组织中脂质过氧化的程度，并导致肝脏组织发生病变。     

饥饿对斜带石斑鱼肝脏和肌肉脂肪酸组成的影响

在室外水泥池(4m×1.5m×1m)进行石斑鱼(62.3±0.6g)的饥饿实验,每池放养35尾,设3个重复,实验时间分别为0、1、2、3和4周。随着饥饿时间的延长,体重减轻,肥满度和肝体比显著降低;肌肉水分显著增加而蛋白质含量显著下降(P<0.05),脂肪含量在第1周下降后基本保持稳定。肝脏饱和脂肪酸在饥饿前3周基本保持不变,第4周显著下降。单不饱和脂肪酸在饥饿第1周保持不变,然后呈下降趋势。多不饱和脂肪酸和高不饱和脂肪酸的总和随着饥饿时间的延长,含量显著增加。与肝脏相比,肌肉中脂肪酸变化程度较小。随着饥饿时间的延长,肌肉中140减少而205增加。饥饿使肌肉中DHA/EPA比率呈下降趋势,但肝脏DHA/EPA比率显著上升;肌肉和肝脏中DHA EPA的百分比都随饥饿时间的延长而显著上升。     

Effects of dietary inclusion of soybean meal and cholesterol on the growth,cholesterol status and metabolism of the giant grouper (Epinephelus lanceolatus)

The study evaluated effects of cholesterol supplementation in a diet with high soybean meal (SBM) on the growth and cholesterol metabolism of giant grouper (Epinephelus lanceolatus). All‐fish‐meal diet was used as control. The diet including SBM (replaced 50% of the fish meal protein, SBM diet) and the SBM diet supplemented with 10 g/kg cholesterol (SBM + cholesterol) were used as experimental diets. Three diets were each fed to triplicate groups of juvenile grouper (initial body weight: 12.39 ± 0.36 g) in a recirculating aquaculture system for 8 weeks. Grouper fed the control diet showed higher (p < .05) weight gain, feed intake, feed efficiency and protein efficiency ratio than the other two dietary treatments. Hepatic cholesterol concentrations and 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase gene expressions were higher in fish fed the control diet than fish fed the control diet and SBM + cholesterol diet. Hepatic cholesterol 7α‐hydroxylase gene expression was higher in fish fed the SBM + cholesterol diet than that in fish fed the control diet. Results indicate that giant grouper on a diet low in cholesterol can regulate cholesterol synthesis, suggesting that the reduced dietary cholesterol intake in the fish fed diet containing SBM is sufficiently compensated by increased cholesterol synthesis.     

Effect of oxidized fish oil on growth performance and oxidative stress of Litopenaeus vannamei

A 4‐week feeding trial was conducted to determine the effects of oxidized fish oil (OFO, POV: 234.84 meq kg^?1) on growth performance and oxidative stress of Litopenaeus vannamei. Five diets containing various OFO levels (0, 25, 50, 75 and 100 g kg^?1) with the same dietary lipid level were fed to L. vannamei. The results showed that the body weight gain and the specific growth rate of the shrimp fed with 50, 75 and 100 g kg^?1 of OFO diets decreased significantly (P < 0.05), whereas the hepatosomatic index increased significantly (P < 0.05). The malondialdehyde concentrations in the serum and muscle of the shrimp fed with 50, 75 and 100 g kg^?1 of OFO diets were significantly higher than that of the shrimp fed with fresh fish oil (P < 0.05). The total antioxidant competence decreased significantly compared with the control group. Therefore, dietary OFO affects the growth performance and increases the oxidative stress of shrimp.