Dietary vitamin E requirement of the red drum Sciaenops ocellatus

A 12-week feeding trial was conducted to establish the minimum dietary vitamin E requirement of juvenile red drum by broken-line regression analysis. The semi-purified basal diet was supplemented with 10, 20, 30, 40, 60 or 80 IU vitamin E kg⁻¹ as all-rac -α-tocopheryl acetate. Juvenile red drum were conditioned by feeding the basal diet for 8 weeks prior to the feeding trial to reduce whole-body vitamin E levels. Then, fish initially averaging 12.2 ± 0.4 g fish⁻¹ (mean ± SD) were fed the experimental diets at a rate approaching apparent satiation for 12 weeks. Weight gain and feed efficiency responses of fish fed diets were significantly ( P  < 0.01) altered by the level of vitamin E supplementation but not strictly in a dose-dependent manner. Vitamin E concentrations in liver and plasma also were significantly ( P  < 0.001) influenced by dietary vitamin E level. Plasma ascorbic acid in fish fed the basal diet tended ( P  = 0.066) to be lower than in fish fed diets containing the various levels of vitamin E. In addition, fish fed the basal diet showed edema in the heart, while fish fed all other diets were normal. Fish fed 60 or 80 IU all-rac -α-tocopheryl acetate kg⁻¹ diet had significantly higher respiratory burst of head kidney macrophages than fish fed all other diets, although dietary effects on hematocrit and neutrophil oxidative radical production were not significant. The minimum dietary vitamin E requirement of juvenile red drum was established based on broken-line regression of liver thiobarbituric acid reactive substances to be 31 mg all-rac -α-tocopheryl acetate kg⁻¹ diet.     

Effect of dietary lipid level on muscle composition in Atlantic salmon Salmo salar

This study was conducted to determine the effects of feeding increasing lipid concentrations (310, 380 and 470 g kg^–1 lipid on dry weight) in diets based mainly on herring byproducts to Atlantic salmon Salmo salar . The diets were isonitrogenous, varying in dietary lipid content at the expense dietary starch. Average fish weight increased from 1.2 kg in April to 2.2–2.7 kg at the end of the feeding trial in September. Significantly greater growth was found in fish fed either the 380 g kg⁻¹ or the 470 g kg⁻¹ lipid diets compared with the 310 g kg⁻¹ lipid diet. Muscle lipid content increased in all dietary groups on a wet weight basis from 7.7 ± 1.4% to 12 ± 3% in salmon fed the 310 g kg⁻¹ lipid diet, and to 16 ± 2% in salmon fed the 380 g kg⁻¹ and 470 g kg⁻¹ lipid diets. In fish of similar weight there was a positive correlation between dietary lipid and muscle lipid concentrations. Low concentrations of muscle glycogen were detected in fish fed each of the diets, while muscle vitamin E concentrations slowly decreased as muscle lipid increased. Muscle fatty acid composition reflected dietary fatty acid profiles, containing similar percentages of total saturated, monoenic and n-3 fatty acids (20:5n-3 and 22:6n-3) in fish from all dietary treatment groups. However, a higher ratio of n-3/n-6 was found in muscle from fish fed the 470 g kg⁻¹ lipid diet compared with the other two groups. Blood chemistry values varied somewhat, but all values were within normal ranges for Atlantic salmon of these sizes.     

The dietary protein requirement of a bagrid catfish, Mystus nemurus (Cuvier & Valenciennes), determined using semipurified diets of varying protein level

Triplicate groups of Mystus nemurus (Cuvier & Valenciennes) were fed isoenergetic semipurified diets containing seven dietary protein levels from 200 to 500 g kg^–1 diet for 10 weeks. Dietary protein was supplied by graded amounts of a protein mixture (tuna muscle meal:casein:gelatine) at a fixed ratio of 50:37.5:12.5. Mystus nemurus fingerlings of initial weight 7.6 ± 0.2 g were fed close to apparent satiation at 2.5% of their body weight per day in two equal feedings. Growth performance and feed utilization efficiency increased linearly with dietary protein level from 202 to 410 g kg^–1 diet and declined with protein levels of 471 g kg^–1 diet or above. Protein efficiency ratio and apparent net protein utilization started to decline when the fish were fed with dietary protein levels exceeding 471 g kg^–1 diet. Fish fed with lower protein diets (202–295 g kg^–1 diet) had significantly ( P  < 0.05) higher carcass lipid content compared with fish fed with higher protein diets. Carcass lipid contents were inversely related to moisture content. Dietary protein did not significantly affect fish carcass protein and ash content. Using two-slope broken-line analysis, the dietary protein requirement for M. nemurus based on percentage weight gain was estimated to be 440 g kg^–1 diet with a protein to energy ratio of 20 mg protein kJ^–1 gross energy. This level of protein in the diet is recommended for maximum growth of M. nemurus fingerlings weighing between 7 and 18 g under the experimental conditions used in this study.     

The influence of different levels of dietary vitamin E on sea bass Dicentrarchus labrax flesh quality

Sea bass Dicentrarchus labrax fillet quality was investigated after feeding with four diets (A, B, C or D) containing different levels of dietary vitamin E (139 mg kg^–1, 254 mg kg^–1, 493 mg kg^–1 and 942 mg kg^–1, respectively). Six-hundred and eighty fish (mean initial weight 208 g) were equally divided into four 20 m³ tanks and fed for 87 days. Filtered seawater with a temperature ranging from 18.2 to 26.3 °C was supplied continuously. At the end of the experiment, fish were stored at 1 °C for 12 days. At one, three, six, nine and 12 days, 20 fish per group were processed for proximate composition, vitamin E and induced thiobarbituric acid reactive substances (TBARs) analyses. No significant differences in proximate composition were registered between groups. The flesh lipid content ranged from 88.0 g kg^–1 (group B) to 96.8 g kg^–1 (group A). Vitamin E fillet content was significantly different between groups, reaching levels of 98.0, 150.7, 225.2 and 302.0 μg g^–1 lipids for group A, B, C and D, respectively. Induced TBARs values were statistically different only for group A compared with the other groups. No significant variations were registered in relation to preservation time. Because of the positive influence of vitamin E on seafood quality and the correlation between its dietary level and flesh deposition, the α-tocopherol content of the diet should be well above fish minimum requirements.     

Phosphorus and calcium requirements in the diet of the American cichlid Cichlasoma urophthalmus (Günther)

An experiment was carried out with Cichlasoma urophthalmus (Günther) juveniles to determine the phosphorus requirement and its interaction with dietary calcium. Twelve isoenergetic and isoproteic diets were prepared using a basal artificial diet containing vitamin-free casein, dextrin, starch, corn oil, fish oil, vitamin mixture and a mineral mixture free of calcium and phosphorus. Calcium and phosphorus levels were determined in the casein. To the basal diets were added different concentrations of phosphorus as potassium monophosphate (0.5, 1.0, 1.5 and 2.5 g kg^–1) and calcium as calcium carbonate (0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0 and 4.0 g kg^–1). These concentrations resulted in varying Ca–P ratios (1:1, 1.33:1, 1.5:1, 1.6:1 and 2.0:1). Calcium and phosphorus concentrations in the water were 84 mg kg^–1 and 0.003 mg kg^–1, respectively. The diet with 0.5 g kg^–1 phosphorus resulted in deficiency signs such as reduced growth, high conversion ratio, high fat content and low bone mineralization. Increased levels of dietary calcium and phosphorus both gave improved growth and mineralization. Mineralization continued to increase with dietary phosphorus levels above that required for maximum growth. The optimum level of phosphorus in the diet was 1.5 g kg^–1, the optimum calcium level was 1.8 g kg^–1 and the optimum Ca–P ratio was 1.3. Carcass lipid levels were inversely related to dietary phosphorus.     

Dietary vitamin E requirement of hybrid striped bass (Morone chrysops female × M. saxatilis male)

This study was conducted to determine the dietary vitamin E requirement of juvenile hybrid striped bass ( Morone chrysops female ×  Morone saxatilis male). Semi-purified diets supplemented with 0.2 mg Se kg⁻¹ from Na₂SeO₃ and either 0 (basal), 10, 20, 40, 60, or 80 mg vitamin E kg⁻¹ as  DL -α-tocopheryl acetate were fed to hybrid striped bass initially averaging 1.8 ± 0.1 g (mean ± SD) for 12 weeks. Fish fed the basal diet, which contained 5.8 mg α-tocopherol kg⁻¹ dry weight, were darker in colour and had reduced weight gain, as well as generally reduced haematocrit values compared with fish fed diets supplemented with vitamin E. In addition, fish fed diets containing less than 20 mg supplemental vitamin E kg⁻¹ had significantly ( P  < 0.05) reduced weight gain and feed efficiency compared with those fed diets supplemented with vitamin E at 20–80 mg kg⁻¹. Dietary supplementation of vitamin E caused incremental increases in the concentration of α-tocopherol in both plasma and liver tissues. However, hybrid striped bass fed graded levels of vitamin E did not exhibit a dose response in terms of ascorbic acid-stimulated lipid peroxidation of hepatic microsomes. Regression analysis of weight gain data using the broken-line model indicated a minimum vitamin E requirement ( ±  SE) of 28 ( ±  3) mg kg⁻¹ dry diet. Based on these data, the dietary vitamin E requirement of hybrid striped bass appears to be similar to that determined for other fish species.     

Effects of dietary phosphorus and lipid levels on utilization and excretion of phosphorus and nitrogen by rainbow trout (Oncorhynchus mykiss). 2. Production-scale study

In a 8-week production-scale experiment at a commercial trout farm, the effects of dietary lipid level and phosphorus level on phosphorus (P) and nitrogen (N) utilization of rainbow trout (initial mean weight 99 g) were assessed. A low-phosphorus, high-lipid experimental diet (457 g protein, 315 g lipid, 9.1 g P  kg^–1 dry diet) was compared with a commonly used commercial diet (484 g protein, 173 g lipid, 13.6 g P  kg^–1 dry diet). P and N budgets were constructed using data from the production-scale experiment and digestibility data for the two diets. In addition, orthophosphate and ammonia-N waste were measured in effluent over one 24-h period. Relative to the commercial diet, the experimental diet resulted in significantly increased feed efficiency ratio, N retention and P retention, and substantially reduced dissolved, solid and total P waste (g kg^–1 dry feed). Although N retention resulting from the experimental diet was higher, this was attributable to higher N (protein) digestibility of the experimental diet. Solid N waste (g kg^–1 dry feed) resulting from the experimental diet was substantially lower, but dissolved N waste (g kg^–1 dry feed) was not significantly different relative to the commercial diet. Mean effluent orthophosphate production (mg day^–1 kg^–1 fish) of fish fed the experimental diet was substantially lower than that of fish fed the commercial diet ( P  < 0.05), but effluent ammonia-N production (mg day^–1 kg^–1 fish) was not significantly affected by dietary treatment.     

Evaluation of carbohydrate rich diets through common carp culture in manured tanks

Four diets (T₀–T₃) were formulated reducing the fishmeal (Indian) component by 100 g kg^–1 from 300 to 0 g kg^–1 and including proportionately increasing quantities of maize. Diets were fed for 120 days at 50 g kg^–1 body weight to triplicate groups of common carp (av. wt. 2.11–2.18 g) stocked at 1 m^–2 in mud bottomed cement tanks (18 m²), fertilized with poultry manure. Fish growth, SGR and FCR in the different treatments were statistically not significantly different ( P  > 0.05). PER was lowest for the 300 g fishmeal kg^–1 diet treatment (diet T₀), increasing with decrease in dietary fishmeal content (diets T₁–T₃). Fish survival ranged from 96.29 to 100%. Diets influenced carcass composition and digestive enzyme activity. A significant increase in lipid deposition was recorded with increasing dietary carbohydrate content. Amylase, protease and lipase activities were higher in fish fed with diets T₂ and T₃. The protein sparing effect of dietary carbohydrate and the economic implication of eliminating fishmeal from the diet are discussed.     

Effects of dietary phosphorus and lipid levels on utilization and excretion of phosphorus and nitrogen by rainbow trout (Oncorhynchus mykiss). 1. Laboratory-scale study

Nutritional strategies to reduce both phosphorus (P) and nitrogen (N) excretion relative to growth of rainbow trout were tested in a 2 × 3 factorial experiment. The two factors were `dietary P level' and `dietary lipid level.' Reduction in dietary P from 14 to 8 g kg^–1 dry diet was achieved by partial substitution of dietary fish meal with a combination of full-fat soyabean meal, corn gluten and spray-dried blood meal. Triplicate tanks of 35 rainbow trout per tank were fed experimental diets for 16 weeks and grew from approximately 40 to 250 g, in 15 °C spring water. All tanks were fed the same percent biomass per day. Diets were isonitrogenous, and dietary energy varied with dietary lipid. Diet digestibility data and results of the experiment were used to construct N and P budgets for the fish fed the various diets. A reduction in dietary fish meal from 500 to 200 g kg^–1 dry diet, corresponding to a reduction in dietary P from 14 to 8 g kg^–1 dry diet, resulted in >50% reductions in both solid and dissolved P waste, but did not affect growth, feed efficiency ratio (FER) or sensory characteristics of rainbow trout. Increasing dietary lipid from 170 to 310 g kg^–1 dry diet led to higher growth rate and FER, and lower total N waste relative to weight gain, but did not change protein retention. Increasing dietary lipid level increased deposition of lipid in whole bodies of rainbow trout, and resulted in discernible differences in sensory characteristics of trout fillets.     

Essentiality of dietary calcium supplement in redlip mullet Liza haematocheila

This study was conducted to determine the essentiality of dietary calcium supplement to redlip mullet Liza haematocheila . Juvenile fish were fed four purified experimental diets containing 2.0 g kg^–1 Ca from calcium lactate (diet 1), no supplemental Ca (diet 2), and 2.0 g and 25.0 g kg^–1 Ca from tricalcium phosphate (TCP, diets 3 and 4), respectively. At the end of the 10-week experiment, growth was significantly lower in fish fed diet 2 than fish fed all other diets. This suggests that redlip mullet do not obtain adequate Ca from sea water. Fish fed diets 3 and 4 showed growth performances similar to fish fed diet 1. However, dietary TCP negatively affected bone mineralization of Zn, Mn, K and Fe. The Ca, Zn and Fe levels in liver were low in fish fed TCP-supplemented diets. From these findings, it may be concluded that a dietary Ca supplement is necessary for redlip mullet. Although this species can use dietary TCP as a Ca source for growth, an easily digestible Ca (monobasic or dibasic) supplement to a TCP-rich diet is also essential to maintain normal mineral levels in tissues.     

Efficacy of silicone-coated ascorbic acid and ascorbyl-2-polyphosphate to fast-growing tiger shrimp (Penaeus monodon)

Growth, survival, tissue ascorbate concentration and collagen content were studied in fast-growing Penaeus monodon fed two ascorbic acid (AA) derivatives. Prior to the experimental trial, shrimp (initial body weight: 0.9 ± 0.4 g) were fed on a diet lacking vitamin C for 5 weeks. During the following 13-week experiment, the shrimp (initial body weight: 8.2 ± 0.7 g) were given one of five squid-meal-based diets. The dietary treatments consisted of a diet lacking vitamin C, two diets supplemented with either 500 or 1000 mg AA kg⁻¹ in the form of silicone-coated AA, and two diets supplemented with either 500 or 1000 mg AA kg⁻¹ in the form of ascorbyl-2-polyphosphate. Shrimp gained 18.3 g in 13 weeks. The AA-free diet group exhibited the lowest growth rate, feed intake and survival (26.8%) after 4 weeks. Hepatopancreatic ascorbate and muscle collagen content were significantly ( P < 0.05) lower in AA-deprived shrimp. At the end of the feeding trial, growth rate and survival were not significantly ( P > 0.05) different among groups fed AA-supplemented diets. Hepatopancreatic and haemolymphatic ascorbate concentrations were significantly ( P < 0.05) higher in groups given ascorbyl-2-polyphosphate than in groups given silicone-coated AA. A supplement of 500 mg AA kg⁻¹ diet in the form of either silicone-coated AA or ascorbyl-2-polyphosphate was adequate for optimal growth. But ascorbate concentrations in tissues remained much below saturation levels with a supplement of 1000 mg AA kg⁻¹ diet. It is questionable whether the established vitamin C requirements for P. monodon are adequate to maintain tissue ascorbate in fast-growing juveniles.     

The need for riboflavin supplementation in high and low energy diets for Atlantic salmon Salmo salar L. parr

A two-factor study was conducted to evaluate the effects of dietary riboflavin and lipid levels on the growth, health performance and riboflavin status of Atlantic salmon ( Salmo salar ). Atlantic salmon parr were fed four fishmeal-based diets with or without supplementation of 20 mg riboflavin kg^–1, at two lipid levels, 150 or 300 g kg^–1. Each diet was fed to triplicate tanks of fish for 12 weeks. Unsupplemented diets contained between 6 and 8 mg riboflavin kg^–1. There were no significant differences in growth as a result of riboflavin supplementation. No mortality or histomorphological changes in eye tissues were observed. Dietary treatments did not affect blood haemoglobin values. After 12 weeks, muscle lipid content seemed to be reduced by riboflavin supplementation irrespective of dietary lipid level. Riboflavin status of whole body, muscle, liver, kidney and eye lenses is reported. Saturation levels of riboflavin in liver and muscle were reached with unsupplemented diets. The concentrations of riboflavin and lipid in liver were negatively correlated. There was a tendency of higher whole body riboflavin concentration in fish fed high-lipid diets. Based on growth, absence of deficiency signs and maximal tissue saturation of riboflavin, it can be concluded that the requirement for riboflavin was met by the natural riboflavin content in the raw materials of the feed. However, independent of dietary lipid level, dietary riboflavin supplementation may increase lipid utilization in rapidly growing salmon parr.     

Dietary Vitamin C Requirement of Hybrid Striped Bass Morone chrysops♀× M. saxatilis ♂

A feeding trial was conducted to determine the dietary vitamin C requirement of juvenile hybrid striped bass Morone chrysops × M. saxatilis . Fish were fed a semi-purified basal diet with 40% crude protein and an energy to protein ratio of 8 kcal/g for a conditioning period of 2 wk. This diet which was not supplemented with vitamin C contained approximately 6-mg vitamin C/kg. Following conditioning, fish (approximately 0.55 g initial weight) were stocked as groups of 20 in 38-L aquaria and fed the basal diet and experimental diets supplemented with 10, 20, 30, 45, 60, 75, or 150-mg vitamin C/kg as ascorbate polyphosphate for a period of 10 wk. Fish fed the basal diet and the diet supplemented with 10-mg vitamin C/kg exhibited signs of vitamin C deficiency including suppressed weight gain, reduced plasma and liver ascorbic acid levels, and abnormalities in isthmus cartilage formation. Plasma and liver ascorbic acid levels generally reflected dietary supplementation with the lowest levels occurring in fish fed the basal diet and higher levels in fish fed the supplemented diets. The minimum dietary requirement (±SE) based on non-linear least squares regression analysis of weight gain was 22 (±6) mg vitamin C/kg diet.     

Effects of dietary protein and lipid level on growth and body composition of juvenile ayu (Plecoglossus altivelis) reared in seawater

A 3 (protein levels, 380, 460 and 520 g kg^–1 diet) × 2 (lipid levels, 65 and 140 g kg^–1 diet) factorial experiment with three replicates was conducted. Weight gain, feed efficiency and daily feed intake were not significantly affected by dietary protein level, but were by dietary lipid level. Weight gains of fish fed 65 g lipid kg^–1 diet were significantly, or slightly, higher than for 140 g lipid kg^–1 diet at all protein levels. Daily protein intake was significantly affected by both dietary protein and lipid levels ( P  < 0.002). Daily lipid intake was not significantly affected by dietary protein level, but was by dietary lipid level ( P  < 0.001). Protein efficiency ratio was significantly affected by dietary protein level ( P  < 0.02), but not by dietary lipid level. Protein efficiency ratio tended to improve with the decrease of dietary protein level at the same lipid level. Moisture, protein and lipid contents of whole fish were significantly affected by dietary lipid level ( P  < 0.01). Increased dietary lipid did not improve growth or feed efficiency, but increased body fat deposition. It was concluded that the optimum dietary protein and lipid level for growth of juvenile ayu may be 380 and 65 g kg^–1 diet, respectively, when fish were fed to satiety three times daily in seawater.     

Dietary Supplementation of a Purified Nucleotide Mixture Transiently Enhanced Growth and Feed Utilization of Juvenile Red Drum, Sciaenops ocellatus

Abstract.— Commercial nucleotide products have been shown to enhance early growth as well as immunity and disease resistance in aquacultured fish. Thus, we investigated effects of a purified nucleotide mixture on growth and health of young red drum. The nucleotide premix, containing salts of cytidine, uridine, adenosine, and guanidine, was coated with binders, freeze-dried, and grounded to powder. A fish-meal-based diet was supplemented with 0.03, 0.1, or 0.3% by weight of the coated nucleotide mixture or with 0.2% Optimûn^® (Chemoforma Co., Basel, Switzerland), a commercial nucleotide product. The experimental diets were maintained isonitrogenous and isocaloric by adjusting amounts of casein, gelatin, and alanine. Five replicate groups of 12 juvenile red drum (10.2 ± 0.2 g/fish, mean ± SD) were fed each experimental diet for 4 wk, followed by an assay of neutrophil oxidative radical production and a bacterial challenge via intraperitoneal injection of Vibrio harveyi at 2.9 × 10⁷ colony-forming units/g fish. Fish fed all diets supplemented with various levels of purified nucleotides showed significantly ( P  < 0.01) enhanced weight gain and feed efficiency during the first week of feeding compared to fish fed the basal diet. However, the dietary effects became less significant during the following 3 wk of feeding. The transient growth-enhancing effect of dietary nucleotides observed in the present study may explain the conventional controversy about nucleotide effects on fish growth. Dietary supplementation with nucleotides had no influence on terminal whole-body composition.     

Methionine requirement of juvenile Japanese flounder Paralichthys olivaceus estimated by the oxidation of radioactive methionine

Growth and amino acid oxidation studies were conducted to estimate methionine requirement of juvenile Japanese flounder, Paralichthys olivaceus , by using the purified diets containing 500 g kg^–1 crude protein from casein, gelatine and crystalline amino acids (CAA). Diets with six graded levels of methionine (5.3, 8.3, 11.3, 14.3, 17.3 and 20.3 g kg^–1 diet) were fed to triplicate groups of the juvenile (initial weight 2.8 ± 0.05 g) twice a day for 40 days. To prevent leaching losses, CAA were precoated using carboxymethylcellulose (CMC), and further diets were bound by CMC and κ-carrageenan. Based on broken-line analysis of percentage weight gain and feed conversion efficiency, the methionine requirements of Japanese flounder in the presence of 0.6 g kg^–1 of cystine were 14.9 and 14.4 g kg^–1 dry diet, respectively. After the growth study was finished, a direct estimate of methionine requirement was made by examining the influence of dietary methionine level on ¹⁴C-methionine oxidation by determining radioactive carbon dioxide, protein and nonprotein fractions of the whole body. The dose–response curve between expired radioactive CO₂ and dietary methionine levels showed that the optimum methionine level for the flounder was estimated to be within the range of 14.3–17.3 g kg^–1 of diet in high agreement with values obtained from the growth study.     

Selenium nutrition of hybrid striped bass (Morone chrysops × M. saxatilis) bioavailability, toxicity and interaction with vitamin E

Two concurrent 12-week feeding trials were conducted to evaluate the bioavailability of inorganic sodium selenite and organic seleno-DL-methionine and to investigate the potential interaction between selenium and vitamin E in juvenile hybrid striped bass. In experiment 1, purified diets utilizing casein, gelatin and an amino acid premix as protein sources with a basal selenium concentration of 0.11 mg Se   kg⁻¹ were supplemented with either Na₂SeO₃ to provide selenium concentrations of 1.19, 2.00, 5.17 and 21.23 mg Se kg⁻¹ or with seleno-DL-methionine to provide 0.90, 1.26 and 2.55 mg Se kg⁻¹ and fed to juvenile hybrid striped bass in aquaria. A second experiment evaluated potential interactions by feeding these purified diets with or without supplemental vitamin E or sodium selenite, singularly or in combination. No overt selenium deficiency signs were exhibited by fish in either of the experiments; however, signs of selenium toxicity including retarded weight gain (WG), reduced feed intake and feed efficiency ratio (FER) as well as increased mortality, were observed in fish fed the diet containing more than 20 mg Se kg⁻¹. Whole-body selenium and whole-body selenium retention were linearly influenced by sodium selenite and selenomethionine. However, there was no significant effect of dietary selenium, vitamin E or their interaction on WG, FER and survival. Slope-ratio analysis showed that bioavailability of seleno-DL-methionine as a selenium source for juvenile hybrid striped bass was significantly ( P  < 0.01) higher (3.3-fold) than sodium selenite.     

Biotin in practical fish-meal based diet for Atlantic salmon Salmo salar L. fry

Groups of Atlantic salmon fry (0.19 g initial weight) were fed a fish-meal based starter diet with different supplements of biotin (0, 0.5, 1.0 and 1.5 mg biotin kg^–1) in triplicate tanks for 18 weeks. The basal diet contained 0.3 mg total biotin kg^–1. The experimental design included a negative control diet made by replacing 10% of the fish-meal with spray-dried raw hen's egg white.
Throughout the experimental period the fish grew to about 5 g and there were no significant differences in growth and mortality among the groups of fish fed the fish-meal diets. At the end of the experiment there were no significant differences in biotin level in the liver, while whole-body biotin concentrations correlated significantly with the dietary biotin concentrations. No significant increase in pyruvate carboxylase (PC) activity was found in livers from fish given different dietary levels of biotin. The control diet with egg white resulted in severe growth reduction and increased mortality compared with the other dietary groups. The concentrations of biotin in liver and whole body were decreased in fish fed egg white. Increased levels of glycogen and reduced PC activity in the liver were observed in this group after 18 weeks.
Histology of the gills showed no differences in appearance when fish were fed fish-meal based diets while the addition of egg white resulted in hypertrophy and hyperplasia of the gill tissue and extensive fusions of the secondary gill lamellae.
The results show that there is no need for supplemental biotin in practical fish-meal based diets for Atlantic salmon fry to achieve optimal growth, survival and maximal liver PC activity.     

Dietary threonine requirement of juvenile hybrid striped bass (Morone chrysops♀×M. saxatilis♂)

Two growth studies were conducted to determine the dietary threonine requirement of reciprocal cross hybrid striped (sunshine) bass. Semipurified diets were prepared with crystalline amino acids and lyophilized fish muscle to supply 350 g crude protein kg⁻¹ diet. The basal diet contained 4.9 g threonine kg⁻¹ from fish muscle, and test diets were supplemented with graded levels of L-threonine. In the first experiment, fish initially averaging ≊ 9.8 g each were fed diets containing threonine levels of 4.9, 7.5, 10.0, 12.5, 15.0 and 17.5 g kg⁻¹ dry diet for 7 weeks. Weight gain, feed efficiency and protein efficiency ratio (PER) were significantly ( P < 0.01) influenced by dietary threonine level. Based on weight-gain responses, a threonine requirement (± SE) of 8.4 (± 0.8) g kg⁻¹ dry diet was determined, and dietary threonine levels of 10.0 g kg⁻¹ diet or greater resulted in the highest levels of free threonine in plasma.
Based on the results of the first experiment, a second feeding trial was conducted with diets containing threonine levels of 4.9, 6.5, 8.0, 9.5, 11.0 and 12.5 g kg⁻¹ dry diet. Fish initially averaging ≊ 3.0 g each were fed each diet for 8 weeks. Weight gain, feed efficiency and PER values of fish were markedly improved, with increases in dietary threonine up to 8.0 g kg⁻¹ dry diet. Regression analysis of weight gain, feed efficiency and PER data using the broken-line model resulted in threonine requirement estimates of 9.7, 8.5 and 8.6 g kg⁻¹ dry diet, respectively. Based on these data, the threonine requirement of juvenile sunshine bass was determined to be ≊ 9.0 g kg⁻¹ dry diet or 26 g kg⁻¹ of dietary protein.     

Myo-inositol prevents oxidative damage, inhibits oxygen radical generation and increases antioxidant enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian)

This study was conducted to evaluate the effects of dietary myo -inositol (MI) on the antioxidant status of juvenile Jian carp ( Cyprinus carpio var. Jian). A total of 1050 Jian carp (22.28±0.07 g) were randomly distributed into seven groups of three replicates each, feeding diets containing graded levels of MI (163.5, 232.7, 384.2, 535.8, 687.3, 838.8 and 990.3 mg kg⁻¹ diet) for 60 days. Results indicated that the malondialdehyde content was the lowest for fish fed diets containing ≥384.2 mg MI kg⁻¹, and the highest for fish fed the MI-unsupplemented basal diet ( P <0.05). The protein carbonyl content was decreased with increasing dietary MI levels up to 535.8 mg kg⁻¹ diet, and no differences were found with a further increase in the MI concentration. The anti-superoxide anion capacity (ASA) and anti-hydroxyl radical capacity (AHR) were increased with increasing MI levels up to 535.8 mg kg⁻¹ diet, and plateaued thereafter. The superoxide dismutase and glutathione- S -transferase activities showed the same tendency with the ASA capacity. Catalase, glutathione peroxidase and glutathione reducase activities were improved with increasing MI levels up to 838.8, 384.2 and 687.3 mg kg⁻¹ diet, respectively, and remained nearly constant thereafter. These results suggested that MI could inhibit oxygen radical generation, increase enzymatic antioxidant capacity and prevent oxidative damage of carp. Dietary MI requirements for ASA and AHR activities of juvenile Jian carp were 567.94 and 517.22 mg MI kg⁻¹ diet respectively.