Effects of dietary L‐carnitine level on growth performance,body composition and antioxidant status in beluga (Huso huso L. 1758)

A 17‐week feeding trial was carried out to evaluate the effects of dietary L‐carnitine level in beluga, Huso huso. A total of fish averaging 1247 ± 15.6 g (mean ± SD) were randomly distributed into 18 fibreglass tanks, and each tank holding 10 fish was then randomly assigned to one of three replicates of six diets with 50, 150, 350, 650, 950 and 1250 mg L‐carnitine kg^?1 diet. At the end of 17 weeks of feeding trial, average weight gain (WG), feed efficiency (FE), protein efficiency ratio (PER) and condition factor (CF) of fish fed 350 mg kg^?1 diet were significantly (P < 0.05) higher than those of fish fed 50, 150, 950 and 1250 mg kg^?1 diets. WG, FE, PER and CF of beluga fed 650 mg kg^?1 diet were also significantly higher than those of fish fed 50, 950 and 1250 mg kg^?1 diets. Whole body and muscle protein were significantly improved by the elevation of dietary L‐carnitine level up to 350 mg kg^?1. Liver superoxide dismutase and glutathione peroxidase activities of fish fed 350 and 650 mg kg^?1 diets were significantly higher than those of fish fed 50, 950 and 1250 mg kg^?1 diets. The dietary L‐carnitine level of 350–650 mg kg^?1 diet could improve growth performance, feed utilization, protein‐sparing effects of lipid, antioxidant defence system and reproductive success. Polynomial regression of WG suggested that the optimum dietary L‐carnitine level was 480 mg kg^?1 diet. Therefore, these results may indicate that the optimum dietary L‐carnitine could be higher than 350 but <650 mg kg^?1 diet in beluga reared in intensive culture conditions.     

Effects of stocking density on haematological parameters,growth and fin erosion of great sturgeon (Huso huso) juveniles

The influence of stocking density (1, 2, 4, 6 and 8 kg m^?2) was investigated on haematological parameters, growth and fin erosion of great sturgeon (Huso huso) juveniles for a period of 8 weeks. The mean weight of fish at the start of trial was 93.13±1.04 g. After 8 weeks of rearing, the mean weight was 362.4, 319.7, 267, 242.1 and 211.1 in densities 1–8 kg m^?2 respectively. The results of this study showed that growth parameters, including condition factor, weight, weight gain, feed conversion ratio, specific growth rate and body weight increase, had a statistically significant difference among treatments (P<0.05). A significant difference (P<0.05) was observed in haematocrit, but the other haematological parameters, including red blood cells, white blood cells (WBC), haemoglobin concentration, mean corpuscular haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin concentration and differential WBC count, showed no significant effect with stocking density (P>0.05). At the end of the experiment, stocking density had no significant effect on plasma cortisol and glucose concentration. The fin length (dorsal, anal, ventral, pectoral and caudal) of fish was measured to calculate the fin index. According to this index, dorsal, anal, ventral and pectoral fins showed no significant difference among treatments (P>0.05), but the erosion of the caudal fin was significantly different between fish held on 6 and 8 kg m^?2 (P<0.05). These results showed that rearing density has a major effect on the growth indices of H. huso. Unlike many other fish, great sturgeon exhibited lower stress responses to high stocking density. This indicates that they are more tolerable to rearing conditions in high stocking densities. With respect to the various effects that density causes on growth, fin erosion and physiological and haematological parameters, better understanding of these phenomena considering different levels of density could have a beneficial impact on many rearing steps of this species.     

Evaluation of the optimum dietary protein level for the maximum growth of juvenile beluga (Huso huso L.1758)

A 10‐week feeding trial was carried out to evaluate the optimum dietary protein level for the maximum growth of juvenile beluga, Huso huso. Fish averaging 1.34 ± 0.07 g (mean ± SD) was randomly distributed into 18 circular fibreglass tanks of 500 L capacity (20 fish per tank). Six iso‐caloric diets were formulated to contain 30 (CP₃₀), 35 (CP₃₅), 40 (CP₄₀), 45 (CP₄₅), 50 (CP₅₀) and 55% (CP₅₅) crude protein (CP). Fish were fed each of the six experimental diets in triplicate groups. At the end of feeding trial, weight gain (WG) and specific growth rate (SGR) in fish fed CP₄₀ and CP₄₅ diets were significantly higher than those of fish fed CP₃₀, CP₃₅, CP₅₀ and CP₅₅ diets (P < 0.05). Lipid retention increased significantly from 24.7% to 31.6%, but protein retention decreased from 54.6% to 35.6% with increasing protein levels from 30% to 50%. Muscle total essential and non‐essential amino acid (EAA & NEAA) concentrations increased with the dietary protein level up to CP₄₅ diets. Muscle total EAA concentrations (%) of fish fed CP₄₅ were significantly higher than those of fish fed CP₃₀, CP₃₅, CP₅₀ and CP₅₅, but there was no significantly different between those of fish fed CP₄₀ and CP₄₅. Muscle total NEAA concentration (%) of fish fed CP₄₅ were significantly higher than those of fish fed CP₃₀ and CP₃₅ diets. Broken‐line analysis of WG suggested that the optimum dietary protein level could be 38.9% for maximum growth performance in juvenile beluga (1.3–77 g).     

Effects of different photoperiods on growth, stress and haematological parameters in juvenile great sturgeon Huso huso

The effects of constant light (24L:00D), no light (00L:24D) and two light–dark periods (18L:06D;12L:12D) on the growth, stress and haematological variables were assessed in juvenile great sturgeon, Huso huso . During the 8-week experimental period, juveniles (22.5 ± 0.6 g) were kept under a 150 lx light intensity in fibreglass tanks (0.8 m², 500 L). Differences in growth were insignificant during the experiment, but lactate levels were higher in the 00L:24D and 24L:00D photoperiods compared with 12L:12D and 18L:06D photoperiods. Cortisol levels did not show differences among the various photoperiods. At the end of the experimental period, fish reared under a 12L:12D photoperiod had higher haemoglobin values and erythrocyte numbers than in the other photoperiods, while no differences were found between groups with regard to haematocrit values or leucocyte numbers. The highest survival rate (89%) was observed in the 12L:12D period in which the levels of lactate and cortisol as stress indicators were minimal. The results indicate that various photoperiods cause different stress levels in juvenile great sturgeon and have no significant effects on growth, at least in short time periods.     

Effects of dietary synbiotic on growth,survival, lactobacillus bacterial count,blood indices and immunity of beluga (Huso huso Linnaeus, 1754) juvenile

This study aimed to determine the effect of synbiotic (Biomin IMBO) as feed additive on beluga (Huso huso) juvenile with an average body weight of 26.45 ± 0.19 g. Experimental diets at which supplemented with 1.0, 2.0 and 4.0 g synbiotic per kg of feed were fed to beluga juvenile, whereas the control group was fed with no synbiotic. After the feeding trial for 8 weeks, growth performance, survival, lactobacillus bacterial count, blood indices and immunity were tested. Even though, some growth performance and feed utilization parameters including WG, SGR and FCR were improved in group fed with 2.0 g kg^?1 synbiotic; however, there were no significant differences (P > 0.05) in growth and feeding parameters between juveniles fed control and synbiotic supplementation diets. In terms of intestinal microbiota, there were no significant differences in total and lactic acid bacteria among treatments (P > 0.05). In addition, there were no significant differences of RBC counts, haematocrit, monocyte, lymphocyte, neutrophil, serum glucose and serum total protein levels between the treatment groups (P > 0.05), but group 2 and 4 g kg^?1 synbiotic showed a significant difference (P < 0.05) in WBC counts and haemoglobin, respectively. Furthermore, alternative complement activity (ACH50) and serum total immunoglobulin (Ig) were significantly increased in 2.0 g kg^?1 synbiotic fed fish (P < 0.05); however, it did not change the lysozyme activity, significantly (P > 0.05). These results indicate that synbiotic improves immunity of beluga sturgeon without detrimentally impacting the growth performance, modulates intestinal microbiota and basic haematological parameters assessed. Thus, we suggest that 2.0 g kg^?1 level of synbiotic may be used as an immunity promoter for beluga sturgeon juvenile.     

The effect of lactic acid bacteria administration on growth,digestive enzyme activity and gut microbiota in Persian sturgeon (Acipenser persicus) and beluga (Huso huso) fry

The aims of this study was to assess the effect of two lactic acid bacteria (LAB), Lactobacillus curvatus and Leuconostoc mesenteroides, originally isolated from gastrointestinal (GI) tract of beluga (Huso huso) and Persian sturgeon (Acipenser persicus), respectively, on growth, survival and digestive enzyme (amylase, lipase and protease) activities and the population level of LAB in the GI tract. The treatments included 10 different groups; control, separate supplements of L. curvatus and Leu. mesenteroides at three different counts [2 × 10⁹, 5 × 10⁹ and 9 × 10⁹ colony forming units (CFU) per gram food] and three combinations of the two LAB (2 × 10⁹ + 2 × 10⁹, 5 × 10⁹ + 5 × 10⁹ and 9 × 10⁹ + 9 × 10⁹ CFU per gram food). The bacteria used in this study were added in lyophilized form to chopped Chironomidae. In the beluga study, highest specific growth rate, survival and improved intestinal enzyme activities were noted in the rearing group fed 9 × 10⁹ L. curvatus per gram food. In Persian sturgeon, the inclusion level of 2 × 10⁹ Leu. mesenteroides had similar positive effect. The ability of LAB to colonize the digestive tract seems to involve host specificity, and our bacteriological results are relevant to initiate future probiotic studies in sturgeons and future directions will be discussed.     

Growth efficiency, body composition, survival and haematological changes in great sturgeon (Huso huso Linnaeus, 1758) juveniles fed diets supplemented with different levels of Ergosan

Growth performance, carcass quality, survival and haematological responses were determined when Huso huso juvenile (41.7±1.8 g) fed diets containing Ergosan (an algal product) at 0, 2.0, 4.0 and 6.0 g kg⁻¹ for 60 days. Each diet was fed to triplicate groups of fish at 10-day intervals (1–10, 20–30 and 40–50 with non-supplemented diets and 10–20, 30–40 and 50–60 with supplemented diets). Results showed that fish fed diets containing Ergosan had significantly higher growth than the control group ( P <0.05). Survival was not different among all dietary treatments ( P >0.05). Food conversion ratio in the fish fed a diet containing 4.0 and 6.0 g kg⁻¹ Ergosan was significantly better than the other treatments ( P <0.05), whereas protein efficiency ratio was not different between experimental diets. Lymphocyte count in the fish fed diets containing Ergosan was higher than the other treatments. Haematocrit, haemoglobin (Hb) concentration, number of erythrocytes, total leucocytes, monocyte, eosinophil, myelocyte, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration were not different between treatments. Neutrophil count in the control group was higher than the fish fed supplemented diets. Furthermore, whole body lipid, moisture and fibre were not different among dietary treatments ( P >0.05) but body protein in the fish fed a diet containing Ergosan at the level of 2.0 and 4.0 g kg⁻¹ was higher than the other treatments. Whole body ash content was higher in the control group. It was concluded that dietary administration of Ergosan can influence some growth and haematological parameters in great sturgeon, H. huso juveniles.     

Effects of dietary inorganic copper on growth performance and immune responses of juvenile beluga,Huso huso

A 12‐week feeding trial was conducted to evaluate the optimum dietary inorganic copper (copper sulphate) in juvenile beluga, Huso huso. Eight semi‐purified diets containing 1.1 (Cu_1.0), 3.5 (Cu_4.0), 7.1 (Cu_7.0), 9.7 (Cu₁₀), 13.1 (Cu₁₃), 25.1 (Cu₂₅), 49.9 (Cu₅₀) and 195 (Cu₁₉₅) mg Cu kg^?1 diet in the form of CuSO₄.5H₂O were fed to fish of initial body weight 8.49 ± 0.32 g and length 11.85 ± 0.66 cm (mean ± SD) in triplicate groups in a flow‐through system. Weight gain (WG) of fish fed Cu₁₀ and Cu₁₃ diets was significantly higher than that of fish fed Cu_1.0, Cu_4.0, Cu₂₅, Cu₅₀ and Cu₁₉₅ diets (P < 0.05). Whole‐body and muscle crude protein increased with dietary Cu up to the supplementation level of 13.1 mg kg^?1 diet and then decreased. Whole‐body lipid content was negatively correlated, while whole‐body ash was positively correlated with dietary copper concentration. Hepatic copper–zinc superoxide dismutase activity of fish fed Cu₁₀ and Cu₁₃ diets was significantly higher than that of fish fed Cu_1.0, Cu_4.0 and Cu₁₉₅ diets. Hepatic thiobarbituric acid‐reactive substances of fish fed Cu₁₃ diet was significantly lower than those of fish fed the other diets except for that of fish fed Cu₁₀ diet. Aspartate aminotransferase, alanine aminotransferase and copper accumulation in tissues increased with dietary copper. Broken‐line analysis of WG suggested that the optimum dietary Cu level was 10.3 mg Cu kg^?1 diet. Therefore, these results may indicate that the optimum dietary Cu levels could be greater than 10.3 mg Cu kg^?1 diet but less than 13.1 mg Cu kg^?1 diet in juvenile beluga, when copper sulphate is used as the dietary source of inorganic copper.     

The effects of oligofructose on growth performance,survival and autochthonous intestinal microbiota of beluga (Huso huso) juveniles

Preliminary experiments were undertaken to investigate the effects of oligofructose on beluga sturgeon (Huso huso) growth performance, survival and culturable autochthonous intestinal microbiota. Juveniles (20 g) were fed diets containing varying levels of oligofructose (10, 20 and 30 g kg^?1) at 2–3% body weight per day for 7 weeks. Compared to the control group, no significant (P > 0.05) effect on growth performance was observed in fish fed diets supplemented with oligofructose at 10 and 20 g kg^?1. However, compared to the 20 g kg^?1 group, feeding oligofructose at 30 g kg^?1 resulted in adverse effects on growth performance. Dietary supplementation of oligofructose at 20 g kg^?1 significantly increased survival rate. Microbiological assessment indicated that the viable culturable autochthonous levels were not affected by dietary oligofructose. Although lactic acid bacteria (LAB) were not a dominant component of the endogenous autochthonous microbiota, LAB levels were significantly elevated in fish fed 20 g kg^?1 dietary oligofructose. This elevated LAB population was able to persist for at least 1 week after reverting the prebiotic group back to a control diet. This study encourages further research on different aspects of oligofructose in sturgeon culture with clear emphasis on optimizing dosage levels.     

Effects of dietary Yucca meal on growth,haematology, non‐specific immune responses and disease resistance of juvenile Nile tilapia,Oreochromis niloticus (Linnaeus, 1758)

A 10‐week feeding trial was conducted to determine the effects of dietary yucca meal supplementation on growth, haematology, non‐specific immune responses and disease resistance in juvenile Nile tilapia, Oreochromis niloticus. Six isonitrogenous and isoenergetic experimental diets were formulated to contain 0% (YMS₀), 0.1% (YMS_0.1), 0.3% (YMS_0.3), 0.5% (YMS_0.5), 1% (YMS_1.0) and 2% (YMS_2.0) dietary yucca meal on the dry weight basis. Results of this study showed a higher growth performance for YMS_0.1 group with significant differences with YMS_0.5, YMS_1.0 and YMS_2.0 groups. In addition, whole‐body protein content of fish fed the YMS_0.1 diet was significantly higher as compared to YMS₀. Plasma lysozyme activity significantly increased in YMS_0.1 group comparing to YMS₀ and YMS_0.5 groups. Respiratory burst activity of phagocytic blood cells was significantly enhanced when fish were fed the YMS_0.1 diet. Results also showed that yucca meal supplementation had moderate effects on glutamic oxaloacetic transaminase and cholesterol levels. After the 14‐day challenge test with Aeromonas hydrophila, cumulative survival of fish fed YMS_0.1 diet was significantly higher than that of fish fed diet YMS₀, YMS_1.0 and YMS_2.0. These results suggest that the optimum dietary yucca meal inclusion level in the diet of juvenile Nile tilapia could be between 0.1% and 0.14% (23.9~33.4 mg kg^?1 saponin) as a feed additive to promote growth, enhance the non‐specific immune responses and increase disease resistance.     

Effects of dietary green tea (Camellia sinensis L) on acute stress responses in sturgeon hybrid (Huso huso ♂ × Acipenser ruthenus ♀)

In aquaculture practices, fish commonly confront environmental alterations and unavoidable stresses. Thus, any substance that could attenuate stress responses could be potentially used in aquaculture. A total number of 90 hybrid sturgeons (Huso huso ♂ × Acipenser ruthenus ♀) with an average weight of 212.6 ± 0.7 g were fed experimental diets containing 0, 50 and 100 mg kg^?1 green tea (Camellia sinensis L) for 6 weeks. Subsequently 15 fish from each treatment were exposed to air for 5 min prior to transfer to the recovery tank. Followed by blood sampling after 1, 2, 5 and 12 h, Serum cortisol increased in all treatments, but the intensity was significantly lower in fish fed green tea compared to the control group. Similarly, the green tea diet attenuated the increase in serum levels of glucose and lactate in comparison to the control. Our results showed that green tea could be added to fish diet to attenuate stress responses in Sturgeon hybrid (Huso huso ♂ × Acipenser ruthenus ♀).     

Effectiveness of l‐ascorbyl‐2‐monophosphate Na/Ca as a vitamin C source for yellowtail Seriola quinqueradiata juveniles

A feeding experiment was conducted to examine the efficacy of a vitamin C (L‐ascorbic acid, AsA) derivative, l ‐ascorbyl‐2‐monophosphate Na/Ca (AMP‐Na/Ca) by comparing to l ‐ascorbyl‐2‐monophosphate‐Mg (AMP‐Mg) in terms of growth, AsA content in tissues, and hematology in yellowtail Seriola quinqueradiata juvenile (1.10 ± 0.01 g). Furthermore, a stress resistance test for the species fed AMP‐Na/Ca was also conducted. In experiment 1, 11 test pellet diets with different levels of AMP‐Na/Ca (0, 12, 43, 88, 440 and 881 mg AsA kg^?1diet) and AMP‐Mg (0, 16, 52, 106, 595 and 1164 mg AsA kg^?1 diet) were formulated and fed to the yellowtail three times per day for 50 days. In both the vitamin C sources, the survival rates of the fish fed diets without supplemental AsA were lower than 50% at day 20, and more than 50% mortality occurred in fish that fed the diets containing 12 or 16 mg AsA kg^?1 after day 30. However, no significant differences were detected in survival and growth among fish that fed the diets containing more than 43 mg AsA kg^?1. Liver and brain AsA concentrations generally increased with increasing dietary AsA level in both sources. In experiment 2, test diets were formulated to contain 43, 88, 440 and 881 mg AsA kg^?1 using AMP‐Na/Ca, and after 60 days of feeding, yellowtail juveniles were subjected to low salinity and air exposure stress. The fish that received diets with 440 mg AsA kg^?1 showed significantly higher tolerance to low salinity stress and higher survival rate in air exposure stress than those of other groups. The present study demonstrated that yellowtail juveniles could utilize AMP‐Na/Ca as an AsA source like AMP‐Mg, and that supplementation of 43–52 mg AsA kg^?1 diet was optimum for normal growth. However, this study showed that dietary inclusion of 440 mg AsA kg^?1 would be necessary to improve stress resistance of this species.     

Effect of dietary GroBiotic®‐A supplementation as a prebiotic on the intestinal microflora,growth performance,haemato‐serological parameters,survival rate and body composition in juvenile beluga (Huso huso Linnaeus, 1754)

The objectives of the present study were to investigate of GroBiotic^®‐A (GBA) on growth, autochthonous intestinal microbiota and haemato‐serological parameters of beluga juvenile. A total of 180 fish (40.82 ± 5.81 g) were fed diets containing graded levels of GBA (0, 5, 10 and 20 g kg^?1 diet) for 8 weeks. No significantly differences in body composition, total viable aerobic bacteria, mean cell volume, mean cell haemoglobin, mean cell haemoglobin concentration, neutrophils, eosinophils, monocytes, albumin, glucose, triglyceride, cholesterol, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase were detected between treatment groups. The fish fed on 10 and 20 g kg^?1 GBA significantly showed higher lactic acid bacteria, final weight, body weight increases, weight gain and lower feed conversion ratio compared with the control and 5 g kg^?1 groups. The group fed 20 g kg^?1 GBA showed a highly significant difference in condition factor, survival rate, final length, total red and white blood cells, lymphocytes, haematocrit, haemoglobin, total protein, total immunoglobulin and lysozyme activity. The specific growth rate of the treatment groups was significantly elevated compared with the control groups. These results indicated that GBA at level 20 g kg^?1 improved growth, welfare and survival of beluga juvenile.     

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.     

Effect of dietary soybean meal and multienzyme on intestine histology of beluga sturgeon (Huso huso)

International Aquatic Research - This study aimed to evaluate the effect of soybean meal and multienzyme supplementation on intestinal histopathology of beluga sturgeon (Huso huso). Nine diets were...     

Soya bean‐based diets plus probiotics improve the profile of fatty acids,digestibility, intestinal microflora,growth performance and the innate immunity of beluga (Huso huso)

This study was conducted to investigate the effect of different methods of using probiotics Bacillus subtilis and Bacillus licheniformis in soya bean‐based diets on the physiology of beluga (Huso huso) (351 ± 4 g). Five experimental diets were formulated to feed beluga for 10 weeks. The results showed that there was no significant difference in weight gain between control (446 g) and 70%SBM‐SPRAY2 (409 g) treatments. Long‐chain polyunsaturated fatty acids in the muscle of beluga fed control (203.2 g/kg) and 70%SBM‐SPRAY2 (166.4 g/kg) diet did not change statistically. Blood performance as a newly introduced factor in individuals fed dietary control (64.06) and 70%SBM‐SPRAY2 (64.33) had higher value as compared with those fed dietary 70%SBM‐DIET2 (61.90) (p < 0.05). Also, total protein (1.68 g/dl) and RBC (0.74 × 10⁶/mm³) in fish fed 70%SBM were statistically lower than other treatments (p < 0.05). Lysozyme, alternative complement activity and total viable counts in beluga fed dietary probiotics were significantly higher than others. In conclusion, feeding fish with the 70%SBM‐SPRAY2 diet improved fish growth and health.     

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

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

Effects of dietary 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.     

Interaction between dietary levels of vitamins C and E on growth and immune responses in channel catfish, Ictalurus punctatus (Rafinesque)

This study was conducted to evaluate the effect of dietary levels of vitamins C (0, 100 and 2000 mg kg⁻¹), E (0, 50 and 500 mg kg⁻¹) and their interaction on the growth performance, liver contents of ascorbic acid and α-tocopherol, haematology and immune response of channel catfish, Ictalurus punctatus . Each diet was fed to catfish in triplicate aquaria to apparent satiation twice daily for 12 weeks. The results indicate that the amount of vitamin E contained in the basal diet (23.1 mg kg⁻¹) was sufficient to promote good growth, feed efficiency and survival, but its supplementation was needed to maintain high haematological values and liver vitamin E. Supplementation of vitamin C (100 mg kg⁻¹) to the basal diet containing 10.5 mg kg⁻¹ was required for good growth, feed efficiency, survival and prevention of vertebral deformity and optimum haematological indices. Liver storage of ascorbic acid and α-tocopherol increased with increasing dietary levels of each vitamin. Dietary vitamin E levels had no effect on liver ascorbic acid content, but increasing dietary vitamin C increased liver α-tocopherol. Some measured immune parameters (serum protein and superoxide anion production) were enhanced by supplementation of vitamin C or E. Chemotaxis ratio and phagocytosis were not affected by treatments.