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 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.     

Effects of moderately oxidized dietary lipid and the role of vitamin E on the development of skeletal abnormalities in juvenile Atlantic halibut (Hippoglossus hippoglossus)

A study was conducted to characterize the effects of oxidized marine fish oil (MFO) on skeletal development in juvenile Atlantic halibut (Hippoglossus hippoglossus) and to determine the role of vitamin E on their bone health and antioxidant defense mechanisms. Juvenile halibut (4.5 ± 0.1 g) were fed six experimental diets containing untreated (peroxide value (POV)  =0.6 meq kg^− 1), mod`rately oxidized (POV = 7.5 meq kg^− 1) and highly oxidized (POV = 15 meq kg^− 1) MFO either with or without α-tocopherol acetate (0 or 300 IU kg^− 1) supplementation for 14 weeks. No significant effects on growth, survival, hepatosomatic indices, or hematocrit were observed among the dietary treatments. Fish fed diets without vitamin E and highly oxidized dietary lipids showed increased hepatic malonaldehyde concentrations indicating a response to oxidative stress. Both muscle and liver α-tocopherol concentrations were significantly lower in fish fed diets without vitamin E supplementation. Alkaline phosphatase levels in serum and bone were increased when vitamin E was present within the diet indicating higher bone formation activity by osteoblasts. Oxidized lipids and lack of dietary vitamin E significantly increased saturated and decreased polyunsaturated hepatic fatty acids. Liver lipids of fish fed diets without vitamin E also exhibited a lower ratio of 22:6n-3 to 22:5n-3 and n-3 fatty acids. The most frequent skeletal deformity observed was scoliosis, spanning the cephalic/prehemal regions, as well as the anterior hemal region of the vertebral column, which increased the frequency according to elevated levels of oxidized dietary lipid. Lordosis was also observed, with no specific pattern along the vertebral column. The pattern and type of abnormalities observed were similar to those reported in an earlier study in halibut from a commercial hatchery.     

Modulation of tissue α-tocopherol in African catfish, Clarias gariepinus (Burchell), fed oxidized oils, and the compensatory effect of supplemental dietary vitamin E

Juvenile African catfish, Clarias gariepinus (Burchell), of mean initial weight 15 g, were fed practical diets containing fresh or rancid oil (1:1 cod liver:corn oil) supplemented with either 20 or 100 mg all-rac-α-tocopheryl acetate per kg dry diet, at 0.03 × body weight per day for 8 weeks. After this time, catfish had grown by at least four times in body weight. Significant ( P < 0.05) inter-treatment differences in final body weight were noted. Clarias fed low-tocopherol: oxidized-oil diets performed least well with regard to growth, though elevated dietary vitamin E partially abrogated this effect. Growth of fish fed fresh-oil diets did not benefit from increased dietary α-tocopherol content. Muscle, liver, plasma, heart and spleen all responded significantly ( P < 0.05) to dietary vitamin E dose. Inclusion of oxidized oil in catfish diets decreased tissue α-tocopherol concentration. Hepatic α-tocopherol concentration (μg α-tocopherol per g liver) was observed to be lowered by 90% by the rancid oil diets. When fish previously fed fresh-oil diets were switched to oxidized: low-tocopherol diets, hepatic α-tocopherol concentration was significantly ( P < 0.05) lowered within 2 weeks. The results highlight the importance of dietary oil quality in modulating tissue α-tocopherol concentrations in African catfish.     

Growth,survival, and fatty acid composition of Indian white shrimp <Emphasis Type="Italic">Fenneropenaeus indicus</Emphasis> (Milne Edwards) fed diets containing different levels of vitamin E and lipid

The objective of this experiment was to determine the effects of two levels of vitamin E (100 and 300 mg/kg diet) along with two levels of lipid (9 and 14%) and their interaction on growth performance of Indian white shrimp and consequently to evaluate the fatty acid composition and lipid stability of its muscle tissue during frozen storage. Growth of juvenile Indian white shrimp was not significantly affected by dietary vitamin E and lipid levels. Muscle lipid content of shrimp fed diets with 14% lipid was significantly higher than that of with 9% lipid. Obvious effects of the increase in dietary lipid level on muscle fatty acid composition were significant decrease in proportion of 16:0 and increase in proportion of 20:5n-3. The content of vitamin E concentration in shrimp muscle reflected dietary vitamin E concentration and ranged from 6.68 to 14.8 mg/kg muscle corresponding to two (100 and 300 mg/kg) levels of vitamin E in fish diet, respectively. Subsequently, results showed that by increasing the concentration of vitamin E from 100 to 300 mg/kg in diet, the rate of lipid oxidation in the muscle tissue during frozen storage was reduced and, as a result, caused higher HUFA retention in muscle of shrimp fed diet with high lipid level.     

Effect of Crude Palm Oil Incorporation on Growth,Survival, Feed Efficiency,and Body Composition of Heterobranchus longifilis Fingerlings

An 8-week feeding trial was carried out to determine the effect of increasing dietary palm oil levels on African catfish juvenile growth and nutrient utilization. Six isonitrogenous diets were formulated to contain 0.5% to 15% crude palm oil with dietary lipid levels ranging from 5% to 20%. Growth performance and protein utilization efficiency of African catfish responded in a positive manner to palm oil addition up to 9% (diet 14% lipid). No further improvement in growth was observed with higher levels of palm oil in the diets, and lower survival was observed with inclusion of 15% palm oil (diet 20% lipid). Whole-body lipid content increased when fish were fed with increasing levels of dietary lipid. Under our experimental conditions, the best growth rate and nutrient utilization were observed with the inclusion of 9% crude palm oil in the diets for African catfish.     

Growth Performance and Proximate and Fatty Acid Compositions of Channel Catfish, Ictalurus punctatus, Fed for Different Duration with a Commercial Diet Supplemented with Various Levels of Menhaden Fish Oil

A 15‐wk study was conducted to evaluate the effect of supplemental menhaden fish oil levels and feeding duration on growth performance and tissue proximate and fatty acid (FA) compositions of juvenile channel catfish, Ictalurus punctatus. Dietary fish oil levels had no effect on final weight gain, feed efficiency, and survival of channel catfish. Tissue lipid contents were directly correlated to dietary lipid levels, while moisture contents were inversely related to dietary lipid levels. Fillet moisture contents progressively decreased, whereas fillet lipid increased with increasing feeding duration. Significant increase in saturated and total n‐3 FAs and decrease in monoenoic and total n‐6 FA in whole body and fillet were observed at each incremental level of dietary fish oil. Percentages of n‐3 and n‐3 highly unsaturated fatty acids in fillet of fish fed the control and 3% fish oil diets decreased with increasing feeding periods, whereas those of fish fed 6 or 9% added fish oil diets remained stable or increased. Ratios of n‐3/n‐6 were statistically comparable throughout the 15‐wk feeding. When expressed in terms of mg/g of fillet, the highest concentration of n‐3 was obtained in fillets of fish fed the 9% added fish oil diet for 15 wk.     

Effects of dietary vitamin E supplementation on growth performance, lipid peroxidation and tissue fatty acid composition of black sea bream (Acanthopagrus schlegeli) fed oxidized fish oil

A 9-week feeding experiment was conducted to evaluate the effects of dietary vitamin E supplementation on growth, lipid peroxidation and fatty acid composition of black sea bream fed oxidized oil. The FL and OL diets contained fresh fish oil and oxidized oil, respectively, without additional vitamin E supplementation. Another four α-tocopherol levels (150, 250, 450 and 800 mg kg⁻¹ diet) were used within the OL diet, giving a total of six experimental diets. Fish were hand-fed to apparent satiation twice daily. At end of the trial, the weight gain and survival rate of fish were significantly reduced by diets with oxidized oil, whereas hepatosomatic index was remarkably high in fish fed oxidized oil diet. However, vitamin E supplementation to diet significantly improved growth performance and increased vitamin E content in the liver. Although, liver thiobarbituric acid reactive substances and docosahexaenoic acid were significantly increased by dietary oxidized oil, their levels were reduced by dietary vitamin E supplementation. Our results indicate that the fish were performing the best at intermediate concentrations of α-tocopherol and a dose of >150 mg α-tocopherol kg⁻¹ diet could reduce lipid peroxidation and improve fish growth performance when oxidized oils exist in diet.     

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.     

Requirement of vitamin E of growing sea cucumber Apostichopus japonicus Selenka

This feeding trial was conducted to determine the vitamin E requirement of growing sea cucumber Apostichopus japonicus Selenka. Six isonitrogenous and isoenergetic experimental diets were formulated to contain graded levels of vitamin E (6.7, 81.2, 159.3, 237.8, 314.6, 395.9 mg/kg diet). Each diet was assigned randomly to 30 growing sea cucumber with initial body weight 15.43 g in triplicates for 8 weeks. Survival rate was not affected by dietary vitamin E; meanwhile, both the weight gain (WG) and specific growth rate were presented the trend of increasing first and then kept stable. With the increasing of dietary vitamin E, crude lipid content of body wall was evaluated firstly and dropped afterwards. When dietary vitamin E contents were lower than 159.3 mg/kg, vitamin E contents of body wall were increased by dietary vitamin E levels, but there were no more differences when dietary vitamin E higher than 159.3 mg/kg. There were minor effects on digestive enzymes of intestine by dietary vitamin E. Contents of malondialdehyde were decreased, while the total superoxide dismutase activity was increased first and then decreased with the increasing of dietary vitamin E. Activities of intestinal alkaline phosphatase were increased, and glutamic oxaloacetic transaminase were decreased first and then increased with the increasing of dietary vitamin E. In conclusion, analysis by a linear regression equation of WG or vitamin E contents in body wall indicated that the optimum requirement of vitamin E for growing sea cucumber (initial body weight 15.43 g) was 165.2–187.2 mg/kg diet.     

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.     

Re-evaluation of vitamin E supplementation of practical diets for channel catfish, Ictalurus punctatus, production

A 10-month feeding trial was performed with channel catfish, Ictalurus punctatus , to re-evaluate the minimum level of dietary vitamin E supplementation required under conditions of commercial production. Four levels (0, 15, 30 and 60 mg kg⁻¹ diet) of supplemental vitamin E were added as DL -α-tocopherol acetate to a typical commercial catfish diet. Sixteen 0.04-ha ponds were stocked in July, at a rate of 25 000 fish ha⁻¹, with two size classes (averaging 18 and 265 g fish⁻¹) of fingerling channel catfish, and each diet was fed to fish in four replicate ponds once daily to satiation. After 10 months of feeding, a total harvest was performed to obtain final production data, and samples were obtained from fish in all ponds. Liver and plasma samples were obtained for α-tocopherol determination, and liver, heart and muscle samples were processed for histological evaluation.
No discernible differences occurred among fish fed the different diets with respect to weight gain or survival. Mean production rate was 9734 kg ha⁻¹, with a final average fish weight of 0.53 kg. A significant ( P < 0.05) effect of diet was noted in plasma and liver α-tocopherol levels, which increased with dietary supplementation. An effect of size also was apparent, with plasma and liver α-tocopherol levels being higher in larger fish compared with smaller fish within a dietary treatment. Histological evaluation revealed no differences among fish fed the different dietary treatments. Based on the lack of overt histological signs of deficiency, it appears that the current level of vitamin E supplementation of commercial catfish diets may be reduced considerably with no detriment to channel catfish health or production.     

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。     

Dietary lipid level and source affect metabolic responses in hybrid catfish (Pseudoplatystoma reticulatum × Leiarius marmoratus)

This study was undertaken to evaluate the effect of dietary lipid source [linseed oil (LO, rich in 18:3 n?3); corn oil (CO, rich in 18:2 n?6); olive oil (OO, rich in 18:1n?9); and fish oil (FO, rich in LC‐PUFA)] and level (9% L and 18% L) on growth, body composition and selected plasma biochemistry parameters in hybrid catfish (Pseudoplatystoma reticulatum × Leiarius marmoratus) juveniles. Moreover, liver histology (lipids, glycogen, cell vacuolization) and key metabolic enzyme activities were also evaluated. After 8 weeks of feeding, there were no differences in growth performance and whole‐body composition between groups. Plasma lipoprotein, muscle and liver composition, and G6PD and ME activity were affected by lipid level and source. No differences were observed between groups in hepatic ALT activity; however, AST activity was lower in fish fed the 9% L diets. Overall, liver and muscle fatty acid composition reflected that of diet FA composition, with increased n3/n6 ratio, high HUFA and low MUFA in fish fed FO compared with the VO diets. Higher liver glycogen content was observed in fish fed the 18% L than the 9% L diets, except for fish fed FO diet. Considering the experimental diets used, these results indicate that hybrid catfish can efficiently utilize VO supplementation as an energy source, without affecting growth performance and fillet composition.     

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 oxidized oil and vitamin E on the growth,blood parameters and body composition of juvenile Atlantic cod Gadus morhua (Linnaeus 1758)

The effects of oxidized dietary lipid and the role of vitamin E on the growth performance, blood parameters and body composition of juvenile Atlantic cod (Gadus morhua) were evaluated over a 9‐week feeding period. Four isonitrogenous experimental diets containing fresh or oxidized fish oil with or without added vitamin E (α‐tocopherol or mixed tocopherols) were fed to juvenile cod. The oxidized lipid used had a peroxide value of 94 mEq kg^?1 oil. No significant (P>0.05) differences in growth performance (weight gain and specific growth rate) or feed utilization (feed consumption and feed efficiency ratio) were observed when oxidized dietary lipid was used. The hepatosomatic index (HSI), viscerosomatic index (VSI) and haematocrit did not show any significant (P>0.05) differences among the treatments. However, erythrocyte osmotic fragility (EOF), referred to as susceptibility to haemolysis, of fish fed oxidized oil without added vitamin E was high in comparison with those fed unoxidized oil. Supplementation with α‐tocopherol appeared to decrease haemolysis, but mixed tocopherols had no significant (P>0.05) effect on EOF. The proximate composition of fish whole body was also affected by diet treatment. Fatty acid composition of liver total lipid reflected that of dietary lipid. Variations in tissue (liver and muscle) fatty acid composition among the treatments followed the same trend as those of the dietary fatty acids. Fish fed fresh oil had a higher proportion of polyunsaturated fatty acids (PUFA) in muscle and liver lipid than those fed oxidized oil. The results suggest that oxidized dietary oil affected juvenile Atlantic cod in certain tissues and that these effects could be alleviated by supplementation of sufficient amounts of vitamin E in the diet.     

Replacement of fish oil with soybean oil in diets for juvenile Chinese sucker (<Emphasis Type="Italic">Myxocyprinus asiaticus</Emphasis>): effects on liver lipid peroxidation and biochemical composition

This study was designed to evaluate the effect of the replacement of fish oil (FO) by soybean oil (SO) on growth performance, liver lipid peroxidation, and biochemical composition in juvenile Chinese sucker, Myxocyprinus asiaticus. Fish (13.7 ± 0.2 g) in triplicate were fed five experimental diets in which 0% (FO as control), 40% (SO40), 60% (SO60), 80% (SO40), and 100% (SO100) FO were replaced by SO. The body weight gain of fish fed SO40, SO60, or SO80 diet was similar to FO group, but diets that have 100% soybean oil as dietary lipid significantly reduced fish growth (P < 0.05). Although the level of SO resulted in increasing crude lipid content of the liver, the level of SO did not significantly alter the hepatosomatic index (HSI). Indicators of peroxidation, such as vitamin E (V_E) and thiobarbituric acid-reactive substance (TBARS) contents, were changed as increasing dietary SO. It was shown that the inclusion of SO in the diets increased V_E concentrations, but reduced TBARS in the liver and total cholesterol (T-CHO) in the plasma. Linoleic acid (LA) and linolenic acid (LNA) significantly increased in fish liver fed diets that contained SO, but eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and the ratio n-3/n-6 were significantly reduced by the inclusion of dietary SO (P < 0.05). Our results indicated that the inclusion of SO increased the hepatic V_E content and reduced lipid peroxidation in fish. However, diet containing 100% SO as dietary lipid could reduce growth performance. Thus, we recommended that 40–80% SO can be used as dietary lipid to replace FO for juvenile Chinese sucker.     

Influence of dietary protein levels on growth performance, carcass composition and liver lipid classes of juvenile Spinibarbus hollandi (Oshima)

A feeding trial was conducted to investigate the influence of dietary protein levels on growth performance, carcass proximate composition and liver lipid classes of juvenile Spinibarbus hollandi (Oshima), a cyprinid fish. White fish meal was the primary protein source in the study. Eight experimental diets containing 13–55% crude protein were fed to three replicate groups of six fish weighing nearly 8.5 g each for 10 weeks. Both percentage weight gain and feed efficiency ratio increased significantly with increasing dietary protein levels up to 31%, but there was no further increase for protein levels from 31% to 55%. Application of broken‐line regression analysis to the percentage weight gain provided an estimate of 32.7±1.5% dietary protein for maximum growth. The protein efficiency ratio and productive lipid value were inversely correlated with dietary protein level. The hepatosomatic index and the viscerosomatic index were also inversely related to dietary protein level. The carcass protein of fish fed lower protein diets was significantly lower than that of the fish fed higher protein diets. Carcass lipid content decreased with increasing dietary protein levels, whereas moisture was inversely related to lipid content. Both liver glycogen and liver lipid contents decreased with increasing dietary protein levels. Triglyceride was the major component in the liver lipid, and the amount of triglyceride deposited in the liver also decreased with dietary protein levels. The results indicated that both carcass proximate composition and liver lipid class of juvenile Spinibarbus hollandi were affected by dietary treatments.     

Effect of dietary iron (Fe) levels on growth performance,hepatic lipid metabolism and antioxidant responses in juvenile yellow catfish Pelteobagrus fulvidraco

This study was conducted to determine effects of dietary Fe levels on growth performance, hepatic lipid metabolism and antioxidant response for juvenile yellow catfish Pelteobagrus fulvidraco. Yellow catfish were fed six isonitrogenous and isolipidic diets containing Fe levels of 16.20, 34.80, 54.50, 76.44, 100.42 and 118.25 mg/kg for 8 weeks. Weight gain (WG) and specific growth rate (SGR) increased with dietary Fe levels from 16.20 to 54.50 mg/kg diet and then plateaued over the level. Feed conversion rate (FCR) was highest and protein efficiency rate (PER) was lowest for fish fed the lowest Fe levels of diet. Fe contents in whole body and liver increased with increasing dietary Fe levels. Hepatic lipid content was lowest, but mRNA levels of carnitine palmitoyltransferase (CPT‐1) and peroxisome proliferator‐activated receptor α (PPARα) were highest for fish fed 54.50 mg Fe/kg diet. Fish fed adequate dietary Fe levels reduced hepatic malondialdehyde (MDA) level and increased activities of antioxidant enzymes Superoxide dismutase (SOD), Catalase (CAT) and GS. Based on the broken‐line regression analysis of WG against dietary Fe levels, optimal dietary Fe requirement for yellow catfish was 55.73 mg Fe/kg diets. Fe‐induced changes in MDA levels and antioxidant enzymatic activities paralleled with the change in hepatic lipid content, suggesting the potential relationship between oxidative stress and hepatic lipid accumulation in yellow catfish.     

Effects of dietary vitamin E on antioxidant defence mechanisms of juvenile turbot (Scophthalmus maximus L.), halibut (Hippoglossus hippoglossus L.) and sea bream (Sparus aurata L.)

In order to enhance growth, survival and quality during early juvenile stages of marine fish it is important to avoid lipid oxidation problems that are known to cause pathologies and disease. The aim of the present study was to characterize and compare the antioxidant systems in juvenile marine fish of commercial importance in European aquaculture, namely turbot (Scophthalmus maximus), halibut (Hippoglossus hippoglossus) and gilthead sea bream (Sparus aurata). The experiment investigated the interaction of the dietary antioxidant micronutrient, vitamin E, with antioxidant defence systems. Fish were fed with diets of identical unsaturation index supplemented with graded amounts of vitamin E. The relationships between dietary and subsequent tissue vitamin E levels were determined as well as the effects of vitamin E supplementation on lipid and fatty acid compositions of both liver and whole fish, on the activities of the liver antioxidant defence enzymes, and on the levels of liver and whole body lipid peroxidation products, malondialdehyde (thiobarbituric acid reactive substances, TBARS) and isoprostanes. Growth and survival was only significantly affected in sea bream where feeding the diet with the lowest vitamin E resulted in decreased survival and growth. A gradation was observed in tissue vitamin E and polyunsaturated fatty acid (PUFA)/vitamin E levels in response to dietary vitamin E levels in all species. The activities of the main radical scavenging enzymes in the liver, catalase, superoxide dismutase and glutathione peroxidase generally reflected dietary and tissue vitamin E levels being highest in fish fed with the lowest level of vitamin E. The indicators of lipid peroxidation gave consistent results in all three species, generally being highest in fish fed with the unsupplemented diet and generally lowest in fish fed with the diet with highest vitamin E. In this respect, isoprostane levels generally paralleled TBARS levels supporting their value as indicators of oxidative stress in fish. Overall the relationships observed were logical in that decreased dietary vitamin E led to decreased levels of tissue vitamin E, and generally higher activities of the liver antioxidant enzymes and higher levels of lipid peroxides.