Effects of dietary n‐3 long‐chain unsaturated fatty acid on growth performance,lipid deposition,hepatic fatty acid composition and health‐related serum enzyme activity of juvenile Japanese seabass Lateolabrax japonicus

Studies were conducted to investigate the effects of dietary n‐3 long‐chain polyunsaturated fatty acid (n‐3 LC‐PUFA) on growth performance, lipid deposition, hepatic fatty acid composition and serum enzyme activities of juvenile Japanese seabass Lateolabrax japonicus (initial mean weight 29.2 ± 1.34 g). Triplicate groups of 30 Japanese seabass were fed with six diets containing grade levels of n‐3 LC‐PUFA (1.30, 2.98, 5.64, 10.31, 14.51, 24.13 g kg^–1 of dry weight) to apparent satiation twice daily for 9 weeks. The specific growth rate (SGR) was the highest in 10.31 g kg^–1 dietary n‐3 LC‐PUFA group. Crude lipid content of the fish decreased significantly with increasing dietary n‐3 LC‐PUFA. Meanwhile, the hepatic lipid content increased significantly in the 24.13 g kg^–1 group. Hepatic n‐3 LC‐PUFA content of total fatty acids was closely correlated with that in diet. No significant difference was observed in serum alanine transaminase (ALT) and aspartate aminotransferase (AST) activities. Moderate n‐3 LC‐PUFA level (10.31 g kg^–1 of dry weight) in the diet was beneficial to enhance the activity of lysozyme in serum. Based on SGR, the optimum dietary n‐3 LC‐PUFA content was estimated to be around 10.94 g kg^–1 of dry weight by second‐order polynomial regression method.     

Long‐chain polyunsaturated fatty acid metabolism in carnivorous marine teleosts: Insight into the profile of endogenous biosynthesis in golden pompano Trachinotus ovatus

Golden pompano Trachinotus ovatus is an important farmed carnivorous marine teleost. Although some enzymes for long‐chain polyunsaturated fatty acid (LC‐PUFA) biosynthesis have been identified, the ability of T. ovatus for endogenous biosynthesis is unknown. Here, we evaluated in vivo LC‐PUFA synthesis in a 56‐day culture experiment using six diets (D1–D6) formulated with linseed and soybean oils to produce dietary linolenic/linoleic acid (ALA/LA) ratios ranging from 0.14 to 2.20. The control diet (D0) used fish oil as lipid source. The results showed that, compared with the corresponding indices of fish fed D0, the weight gain rate and specific growth rate as well as the contents of eicosapentaenoic (EPA) and docosahexaenoic acids in tissues (liver, muscle, brain and eye) of D1–D6 groups were significantly lower (p < .05). These data suggested that T. ovatus could not synthesize LC‐PUFA from C₁₈ PUFA or such ability was very low. However, tissue levels of 20:4n‐3 in fish fed diets D1–D6 were higher than that of D0 fish (p < .05), and positively correlated with dietary ALA/LA ratio, while levels of EPA showed no difference among the D1–D6 groups. These results indicated that Δ5 desaturation, required for the conversion of 20:4n‐3 to EPA, may be lacking or very low, suggesting incomplete LC‐PUFA biosynthesis ability in T. ovatus.     

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 ascorbate on lipogenesis and lipolysis activities in black sea bream, <Emphasis Type="Italic">Acanthopagrus schlegelii</Emphasis>

To assess the effect of dietary ascorbate on lipid metabolism, 1-year black sea bream (Acanthopagrus schlegelii) were reared on a casein-based purified diet and an ascorbate fortified diet (1,100 mg of l-ascorbyl-2- monophosphate-Mg/kg diet). The fortified ascorbate was effectively incorporated into the fish body and elevated muscle carnitine content. Fortifications of dietary ascorbate depressed activities of glucose-6-phosphate dehydrogenase and NADP-isocitrate dehydrogenase as lipogenic enzymes in the hepatopancreas and intraperitoneal fat body. Starvation after feeding experiment activated carnitine palmitoyltransferase as a lipolysis enzyme in the hepatopancreas in both control and vitamin C(VC) groups, while the lipolysis activity was significantly higher in VC group. These results confirmed that dietary ascorbate depressed lipogenesis and activated lipolysis, i.e., influenced the lipid metabolism of black sea bream.     

Diet,size and location as determinants of n‐3 long‐chain polyunsaturated fatty acid content in farmed Atlantic Salmon (Salmo salar)

We explored how currently manufactured feeds, under real‐world conditions and across geographically distinct locations, promoted flesh n‐3 long‐chain polyunsaturated fatty acid (LC‐PUFA, i.e. 20:5n‐3 + 22:6n‐3) levels in various life stages of farmed Atlantic Salmon (Salmo salar). Potential effects on flesh LC‐PUFA included: (1) diet and fish weight at one Canadian east coast farm, (2) diet and farm location across six east coast farms, and (3) diet and farm location between east and west coast farms. For objectives 1 and 2, salmon were fed a currently manufactured feed (labelled as feeds A, B or C) and harvested at 1, 3 and 5 kg. LC‐PUFA levels in 5 kg (harvest size) fish were then compared to previously published values for west coast farmed Atlantic Salmon (Obj. 3). Combined results revealed that variability in LC‐PUFA levels was better explained by diet than by fish weight or farm location. Fish size, however, was also important for two reasons. First, feeding a high LC‐PUFA diet early in life appeared important for ensuring high LC‐PUFA levels at harvest size. Second, salmon flesh LC‐PUFA levels increased with fish size, but only when dietary LC‐PUFA was provided above an apparent threshold value (~3000 mg per 100 g or 10% of total fatty acids) that likely promoted LC‐PUFA incorporation and storage. Overall, our comparison makes new recommendations for feed manufacturers and demonstrates that farmed Atlantic Salmon reared under real‐world conditions on currently available salmon feeds were good sources of n‐3 LC‐PUFA to consumers.     

Effect of dietary saturated and monounsaturated fatty acids in juvenile barramundi Lates calcarifer

Barramundi (Lates calcarifer), a catadromous teleost of commercial interest, perform well when fed a wide range of dietary oils. However, the range of alternative oils now being explored is typically rich in saturated and monounsaturated fatty acids (SFA and MUFA). In this study, the response of juvenile barramundi (47.0 g per fish initial weight) fed isolipidic and isoenergetic diets with 82 g kg^?1 added oil was tested. The experimental test diets had a 2 : 1 or 1 : 2 ratio of SFA to MUFA (SFA‐D and MUFA‐D, respectively) compared to a control diet (CTRL‐D) fed for 8 weeks. The diets containing mostly olive oil (dietary MUFA‐D) and mostly refined palm oil (dietary SFA‐D) did not impact the growth performance or feed utilization parameters of the barramundi. The in vivo beta‐oxidation activity was consistent with the dietary fatty acid composition, with the most dominant FA being heavily beta‐oxidized. Together, the in vivo whole‐body mass balance of fatty acids showed that n‐3 long‐chain polyunsaturated fatty acids (LC‐PUFA) were most efficiently utilized in the SFA‐D‐ and MUFA‐D‐fed fish. This study provides evidence that additional dietary MUFA and SFA are suitable lipid classes for juvenile barramundi and they are both equally efficient at sparing LC‐PUFA from an oxidative fate.     

Effect of dietary canthaxanthin on the growth and lipid composition of red porgy (Pagrus pagrus)

A 24‐week feeding trial was conducted to study the possible effect of dietary canthaxanthin on red porgy growth and lipid composition. Two triplicate groups were established to test two experimental diets: (1) Control group fed a diet with no added carotenoids, and (2) canthaxanthin group (CTX100) fed a diet with 100 mg of synthetic canthaxanthin per kilogram of diet (CTX). Final and eviscerated weight were increased (P < 0.05) in the CTX100 treatment. The rest of growth performance parameters were not affected by the CTX diet. Whole‐fish total lipid content was decreased (P < 0.05) in CTX100 fish. In the liver, total lipids were not affected; however, saturated fatty acids in CTX100 treatment were significantly lower together with a higher n‐3 PUFA and a lower n‐6 PUFA, therefore increasing the n‐3/n‐6 ratio. Liver histology of CTX100 fish revealed decreased lipid vacuolization thus, significantly lowering hepatocyte area. In the muscle, total lipids were not affected. Similar to the liver, an increase of n‐3 PUFA and decrease n‐6 PUFA, led to a significant increase of the n‐3/n‐6 ratio. Concerning plasma, only total cholesterol (TC) was significantly affected by the CTX diet. Dietary canthaxanthin has an effect on red porgy lipid composition.     

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.     

Effects of replacement of dietary fish oil with soybean oil on growth performance and tissue fatty acid composition in marine herbivorous teleost Siganus canaliculatus

Fish oil (FO) substitution has been studied in many marine carnivorous fish, but seldom in marine herbivorous or omnivorous species. To evaluate the feasibility of using soybean oil (SO) as a dietary lipid and confirm its capability of converting C₁₈ polyunsaturated fatty acid (PUFA) into long chain polyunsaturated fatty acid (LC‐PUFA) in the marine herbivorous teleost Siganus canaliculatus, juvenile fish were fed with four formulated diets differing in lipid composition, with SO accounting for 0.76% (SO0), 23% (SO23), 45% (SO45) and 67% (SO67) of total dietary lipid respectively. After feeding for 8 weeks, growth performance including weight gain, specific growth rate, feed conversion ratio and protein efficiency rate were better in the SO23 and, especially, SO45 groups than in the SO0 and SO67 groups (P < 0.05). Tissue fatty acid compositions were affected by diet, with the liver contents of eicosapentaenoic (EPA), docosapentaenoic (DPA), docosahexaenoic (DHA) acids and total n‐3 PUFA displaying parallel changes with the corresponding dietary fatty acids. While the muscle contents of EPA, DPA and total n‐3 PUFA between SO0 and SO23 groups, and the liver contents of arachidonic acid (ARA) and 20:4n‐3, as well as the muscle content of 20:3n‐6 between SO0 and SO45 groups showed no difference, confirming the biosynthesis of LC‐PUFA from C₁₈ precursors in vivo as the contents of corresponding fatty acids in diets SO23/SO45 were much lower than those in diet SO0 (P < 0.05). The results indicate that SO may be a suitable dietary lipid source for S. canaliculatus, and can replace up to 67% or 45% of total dietary FO without negatively compromising growth performance or nutritional quality of fish respectively. Moreover, the study increases our knowledge of FO substitution in marine herbivorous fish.     

Dietary protein requirement of the high altitude's representative teleost juveniles Schizopygopsis younghusbandi (Cypriniformes: Cyprinidae)

A 60‐day trial was conducted to investigate the effect of dietary protein on growth, whole‐body composition, hepatopancreas enzymes, digestion and absorption in the juveniles of Schizopygopsis younghusbandi. Six graded levels of dietary protein (200.0, 248.7, 303.5, 351.2, 395.8 and 449.3 g/kg diet) were formulated and assigned to triplicate groups of 60 fish (8.16 ± 0.02) for each aquarium. Results showed a significantly increased specific growth rate (SGR) in fish fed protein containing 351.2 g/kg diet (p < .05). Besides, intestinal ratio (IR), intestinal somatic index (ISI) and hepatosomatic index (HSI) were decreased and the condition factor (CF) was increased with dietary protein up to 351.2 g/kg diet, then altered reversely. Fish fed the optimal dietary protein showed the highest crude protein calcium, phosphorous and lowest crude lipid contents of the whole body in fish. Additionally, plasma ammonia content (PAC), and activities of GOT and GPT were enhanced by dietary protein levels (p < .05). The digestive enzymes of hepatopancreas were generally increased with the quadratic response to dietary protein levels. Optimal dietary protein level increased the intestinal enzyme activities of Na⁺, K⁺‐ATPase (NKA), alkaline phosphatase (AKP), gamma‐glutamyl transpeptidase (γ‐GT) and creatine kinase (CK). Based on the 2‐slope broken‐line model analysis of PWG, dietary protein requirement was determined to be 349.6 g/kg diet.     

Aurantiochytrium sp. meal as DHA source in Nile tilapia diet,part II: Body fatty acid retention and muscle fatty acid profile

Nile tilapia juveniles (8.35 ± 0.80 g) were fed on four levels (0.0%; 0.5%; 1.0%; 2.0%, 4.0%) of Aurantiochytrium sp. meal (ALL‐G‐RICH?), a source of docosahexaenoic acid (DHA). The 1% Aurantiochytrium sp. meal diet was compared to a control diet, which contained the same amount of DHA as cod liver oil (CLO) at 1.7% diet. Groups of 25 fish were stocked in 100 L tanks and fed twice daily until apparent satiation, for 57 days, at 28°C. Increasing dietary Aurantiochytrium sp. meal reduced the body retention of DHA and n‐3 polyunsaturated fatty acids (n‐3 PUFA) but increased the body retention of alpha‐linolenic (α‐LNA), linoleic (LOA) and n‐6 polyunsaturated fatty acids (n‐6 PUFA). Fatty acid profile in tilapia muscle was affected by increasing dietary inclusions of Aurantiochytrium sp. meal, with an increase in DHA, α‐LNA, n‐3 PUFA and n‐3 long chain‐polyunsaturated fatty acids (n‐3 LC‐PUFA) but a decrease in monounsaturated fatty acids (MUFA), n‐6 PUFA and n‐6 long‐chain polyunsaturated fatty acids (n‐6 LC‐PUFA). There was a larger body retention of DHA, α‐LNA, LOA, n‐3 PUFA and n‐6 PUFA fatty acids and a higher percentage of DHA, n‐3 PUFA and n‐3 LC‐PUFA in muscle fatty acid profile in fish fed on CLO diets than in those fed on 1% Aurantiochytrium sp. Therefore, Aurantiochytrium sp. meal is an alternative source of DHA for Nile tilapia diets.     

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.     

Effects of totally replacing dietary fish oil by linseed oil or soybean oil on juvenile hybrid sturgeon,Acipenser baeri Brandt♀×A. schrenckii Brandt♂

The growth performance, body composition, fillet fatty acid content, serum hepatic enzymes and postprandial changes in serum lipid metabolism of hybrid sturgeon (70.8 ± 0.5 g) were investigated to determine the effects of total replacement of 80 g kg^‐1 fish oil (diet A) with linseed oil (diet B) and soybean oil (diet C), respectively. No significant differences in weight gain rate and specific growth ratio were observed among all fish groups (p > .05). Diet A fish group had the highest, but diet B fish group had the lowest feed intake (p < .05). Feed efficiency of fish fed diet A was significantly lower than the other two fish groups (p < .05). Fish fed diet A had the lowest fillet and liver lipid contents (p < .05). Serum lactate dehydrogenase, alanine aminotransferase and aspartate aminotransferase activities of fish fed diet A were significantly lower than those of fish fed diets B and C (p < .05). The contents of linoleic acid (C18:2n6) and linolenic acid (C18:3n3) in fillets showed a significantly positive linear correlation with the diets. Serum glucose and non‐esterified fatty acid were just affected by the time point (p < .05). The lipid source, time point and interaction of both factors had significant effects on serum triglyceride, high‐density lipoprotein cholesterol and low‐density lipoprotein cholesterol (p < .05). Serum total cholesterol was only affected by interaction of time point and lipid source (p < .05), and ketone body was not affected by lipid source, time point or interaction of both factors (p > .05). In summary, total replacement of fish oil with linseed oil or soybean oil had no significant adverse effects on hybrid sturgeon growth during 84‐day period, and linoleic acid and linolenic acid in fillet were modified by dietary treatments.     

Effects of different dietary lipid sources on growth performance,antioxidant enzyme activities and biochemical composition of juvenile swimming crab,Portunus trituberculatus

An 8‐week feeding trial was conducted to evaluate the effects of dietary lipid sources on growth performance, antioxidant enzyme activities and biochemical composition of juvenile swimming crab Portunus trituberculatus of initial weight 2.34 ± 0.08 g. Four different diets were formulated to contain fish oil (FO), soybean oil (SO), linseed oil (LO) or palm oil (PO). The highest final body weight, weight gain, specific growth rate and molting frequency were observed in crabs fed the FO diet. Crabs fed the SO diet showed higher glutathione peroxidase, superoxide dismutase (SOD) and catalase (CAT) activities in both serum and hepatopancreas than those fed the FO diet. The lowest malondialdehyde concentration in hepatopancreas and serum were occurred at crabs fed the SO diet. Crabs fed the LO diet had significantly higher SOD and CAT activities in hepatopancreas compared with those fed the FO diet. Crabs fed the PO diet had the highest activities of fatty acid synthase and carnitine palmitoyltransferase 1 activities in hepatopancreas among all treatments. Fatty acid compositions both in hepatopancreas and muscle reflected those of diets. Overall, these findings demonstrated that physiological–biochemical characteristics and lipid metabolism were significantly regulated by different dietary lipid sources. Moreover, dietary SO and LO supplementation could improve antioxidant ability.     

Effects of dietary tea polyphenols on growth,biochemical and antioxidant responses,fatty acid composition and expression of lipid metabolism related genes of large yellow croaker (Larimichthys crocea)

The study was conducted to investigate the effects of dietary tea polyphenols (TP) on growth performance, biochemical and antioxidants responses, fatty acid composition, and lipid metabolism‐related gene expressions of large yellow croaker (Larimichthys crocea). Four diets were formulated with different levels of TP (0.00%, 0.01%, 0.02% and 0.05%). Results showed that growth performance of L. crocea were not different among dietary treatments. Compared with the control group, fish in 0.02% TP group had lower body and hepatic lipid content and lower total cholesterol content. The minimum content of triglycerides and low‐density lipoprotein‐cholesterol were found in 0.05% TP group. Hepatic n‐6 PUFA and n‐3 PUFA were significantly higher in TP supplementation groups. Malondialdehyde content was lower in TP supplementation groups, and superoxide dismutase activity was higher in 0.01% TP group than the control group. The mRNA expressions of carnitine palmitoyltransferase1, acyl‐CoA oxidase and peroxisome proliferators‐activated receptor α were up‐regulated in 0.01% and 0.02% TP groups, while lipoprotein lipase expression was down‐regulated in TP supplementation groups than the control group. Results suggested that 0.01%–0.02% TP supplementation could reduce the deposition of liver lipid of L. crocea caused by high‐lipid diet, which might be due to the increase in lipid oxidation related gene expressions.     

Influence of dietary nucleotides supplementation on growth,body composition and fatty acid profile of Beluga sturgeon juveniles (Huso huso)

Effect of different levels (0%, 0.15%, 0.25%, 0.35% and 0.50%) of Optimûn, a commercial nucleotide (NT) product, on the growth performance, body composition and fatty acid profile of juvenile Beluga sturgeon (Huso huso) (12.57 ± 0.5 g) was investigated over a 62‐day period. This experiment was done in fifteen 600 L tanks, each stocked with 30 fish. Fish fed nucleotide showed significantly better growth performance (P < 0.05). Incorporation of 0.25% and 0.35% NT resulted in whole body protein content elevation, but the other proximate composition indices were not influenced by dietary nucleotide treatments. There were significant differences in saturated fatty acids (SFA) and total unsaturated fatty acids (TUFA) levels among fish fed on different experimental diets, while monounsaturated fatty acids, polyunsaturated fatty acids (PUFA), n‐3 PUFA, n‐6 PUFA, n3/n6 and eicosapentaenoic acid + docosahexaenoic acid were not influenced by NT. The results showed that diet supplementation with 0.35% Optimûn (NT) enhance growth performance, also administration of 0.25% and 0.35% affected chemical composition, as well as decreased SFA/TUFA ratio of Beluga juvenile.     

Separate and combined effects of cyclic fasting and l‐carnitine supplementation in red porgy (Pagrus pagrus,L. 1758)

We examined the effects of cyclic fasting in red porgy (Pagrus pagrus) fed different dietary carnitine levels. Juvenile fish (23.58 ± 3.49 g) were divided into eight groups – four groups were fed every day to apparent satiation, while the other four were fasted for 7 days every 2 weeks. In each feeding regime, two replicates were fed an l ‐carnitine non‐supplemented diet (46 mg kg^?1) and the other two groups were fed an l ‐carnitine supplemented diet (630 mg kg^?1). Fish fed 630 mg l ‐carnitine accumulated two times more l ‐carnitine in muscle than fish fed 46 mg l ‐carnitine. Cyclic fasting reduced the growth performance and lipid content in the liver. Carnitine supplementation did not affect performance and body composition, but decreased the n‐6 PUFA content. Moreover, the combined effects of fasting and carnitine supplementation were observed on reducing the n‐3 fatty acid content. Areas of steatosis were found in the livers of red porgy, but the results revealed that supplementation of l ‐carnitine in cyclic fasted fish contributed towards a lower degree of vacuolization than in fish fed to apparent satiation. Regardless of the feeding regime applied, the spleen of fish fed the l ‐carnitine‐supplemented diet was haemorrhagic and hyper activation of melanomacrophage cells was observed.     

Growth,antioxidant capacity,intestine histology and lipid metabolism of juvenile red claw crayfish,Cherax quadricarinatus,fed different lipid sources

Five dietary lipid sources (fish oil, soybean oil, palm oil, rapeseed oil and linseed oil) were evaluated in juvenile red claw crayfish, Cherax quadricarinatus, based on the response of growth, antioxidant capacity, intestine histology, whole‐body composition, fatty acid nutrition and lipid metabolism. Crayfish were fed in quadruplicate net cages for 8 weeks. Crayfish fed diets with fish oil, soybean oil and linseed oil obtained significantly higher weight gain and specific growth rate than those fed the other two diets. Survival, condition factor and hepatosomatic index were not significantly affected by lipid sources. Lipid sources also do not affect the whole‐body composition of crayfish. Serum SOD, T‐AOC and GSH‐PX activities of crayfish fed the palm oil and rapeseed oil diets had a significantly lower value than those fed other diets. The minimum concentrations of MDA have been observed in crayfish fed the soybean oil diet. The activity of ACC in the hepatopancreas of crayfish fed the linseed oil diet showed the highest value, and the CPT‐1 activity was not significantly affected by different lipid sources. Crayfish fed the soybean oil diet showed significantly higher TC and TG contents in hepatopancreas than those fed other diets. Crayfish fed linseed oil diet had a significantly higher percentage of EPA, C18:3n?3 and Σn?3 PUFA in muscle than those fed other treatments. Most of the fatty acid compositions in the hepatopancreas had a close correlation to fatty acid compositions in diets. All findings in this study indicate that soybean oil is the advantageous lipid source for juvenile C. quadricarinatus which can reflect in satisfactory growth performance, antioxidant capacity and fatty acid nutrition of edible tissues.