Improved digestibility of plant ingredient‐based diets for European seabass (Dicentrarchus labrax) with exogenous enzyme supplementation

This study evaluated the effect of supplementation of a plant ingredients‐based diet with two levels of commercially digestive enzyme products: Synergen? and Natugrain^® on the apparent digestibility coefficients (ADCs) of nutrients and on digestive enzyme activities in European seabass (Dicentrarchus labrax) juveniles. A control diet was formulated with 450 g/kg CP (200 g/kg from fish meal + 800 g/kg from plant protein) and 180 g/kg CL (fish oil), and four other diets were made similar to the control but supplemented with 0.2 g/kg or 0.4 g/kg of Synergen? and Natugrain^®. Digestive enzyme activities were not affected by dietary treatments. Nevertheless, chyme pH along the intestine of fish fed the Natugrain^®‐supplemented diets was reduced. The ADC of nutrients increased with exogenous digestive enzyme supplementation, with the highest ADC values being observed for the 0.4 g/kg Natugrain^® diet. The ADC of dry matter, protein, lipids, energy and phosphorus in this diet were 26%, 6%, 4%, 16% and 63% higher, respectively, than in the control diet. Overall, diet supplementation with exogenous enzyme complexes seems to have high potential for improving the utilization of plant feedstuff‐rich diets for seabass juveniles. This study revealed that Natugrain^® was more effective than Synergen? in improving the ADC of nutrients and energy in European seabass juveniles.     

Requirements of vitamin C (l-ascorbyl-2-sulphate and l-ascorbyl-2-polyphosphate) and its effects on non-specific immune responses of grouper, Epinephelus malabaricus

An 8‐week feeding trial was conducted to determine two vitamin C derivatives, l ‐ascorbyl‐2‐sulphate (C2S) and l ‐ascorbyl‐2‐polyphosphate (C2PP), to satisfy vitamin C requirement and to test their effects on the non‐specific humoral immune responses of juvenile grouper, Epinephelus malabaricus. C2S and C2PP were each supplemented at 20, 50, 80, 150, 250 and 400 mg kg^?1 diet in the semi‐purified basal diet providing of 7, 16, 28, 55, 86, 142 mg ascorbic acid (AA) equivalent of C2S kg^?1 diet and 4, 9, 15, 31, 49, 75 mg AA equivalent of C2PP kg^?1 diet, respectively. Basal diet without AA supplemented was included as a control. Each diet was fed to triplicate groups of grouper (mean initial weight: 6.69 ± 0.07 g). Fish fed diets with ≥28 mg AA equivalent of C2S or ≥4 mg AA equivalent of C2PP kg^?1 had significantly (P < 0.05) greater weight gain (WG) than fish fed the unsupplemented control diet. Liver AA concentrations were higher in fish fed diets with ≥16 mg AA equivalent of C2S or ≥9 mg AA equivalent of C2PP kg^?1 than fish fed the control diet. Alternative pathway of complement activation (ACP) was higher in fish fed diets with ≥55 mg AA equivalent of C2S or ≥15 mg AA equivalent of C2PP kg^?1 than fish fed the control diet. Lysozyme activity was higher in fish fed ≥86 mg AA equivalent of C2S or ≥15 mg AA equivalent of C2PP kg^?1 than fish fed the control diet. Analysis by broken‐line regression of WG indicated that the adequate dietary vitamin C concentration from each vitamin C derivative in growing grouper is 46.2 mg AA equivalent of C2S kg^?1 diet and 17.8 mg AA equivalent of C2PP kg^?1 diet, and it also indicated that C2S is approximately 39% as effective as C2PP in meeting the vitamin C requirement for grouper. The data suggest that both C2S and C2PP supplementation support non‐specific immune responses of grouper.     

Requirements of vitamin C (L-ascorbyl-2-monophosphate-Mg and L-ascorbyl-2-monophosphate-Na) and its effects on immune responses of grouper, Epinephelus malabaricus

An 8‐week feeding trial was conducted to evaluate two vitamin C derivatives, L‐ascorbyl‐2‐monophosphate‐Mg (C2MP‐Mg) and L‐ascorbyl‐2‐monophosphate‐Na (C2MP‐Na), to satisfy the vitamin C requirement and to test their effects on the immune responses of juvenile grouper, Epinephelus malabaricus. C2MP‐Mg and C2MP‐Na were each supplemented at 20, 50, 80, 150, 250, and 400 mg kg^?1 diet in the basal diet providing of 7, 18, 31, 51, 93, 145 mg ascorbic acid (AA) equivalent of C2MP‐Mg kg^?1 diet and 4, 10, 17, 31, 47, 77 mg ascorbic acid (AA) equivalent of C2MP‐Na kg^?1 diet, respectively. Basal diet without AA supplementation was included as control. Each diet was fed to triplicate groups of grouper (mean initial weight 3.20 ± 0.05 g). Fish fed diets supplemented with either C2MP‐Mg or C2MP‐Na had significantly (P < 0.05) greater weight gain (WG), feed efficiency and survival than those fed the unsupplemented control diet. Liver ascorbate concentrations in fish generally increased as dietary C2MP‐Mg or C2MP‐Na supplementation level increased. Haemolytic complement activity was higher in fish fed diets supplemented with 92 mg AA equivalent of C2MP‐Mg kg^?1 or 10–17 mg AA equivalent of C2MP‐Na kg^?1 than fish fed the unsupplemented control diet. Lysozyme activity was higher in fish fed ≥51 mg AA equivalent of C2MP‐Mg kg^?1 or ≥47 mg AA equivalent of C2MP‐Na kg^?1 than fish fed the unsupplemented control diet. Analysis by broken‐line regression of WG indicated that the adequate dietary vitamin C concentration from each vitamin C derivative in growing grouper is 17.9 mg AA equivalent of 2MP‐Mg kg^?1 and 8.3 mg AA equivalent of C2MP‐Na kg^?1, and it also indicated that C2MP‐Mg is about 46% as effective as C2MP‐Na in meeting the vitamin C requirement of grouper.     

Effects of Dietary Ascorbic Acid on Growth Performance,Body Composition,and Some Immunological Parameters of Caspian Brown Trout,Salmo trutta caspius

A 9‐wk feeding experiment was conducted to investigate the effect of dietary ascorbic acid (AA) on growth performance and tissue compositions of Caspian brown trout. The fish (9.64 ± 0.62 g) were held in tanks at a density of 40 fish per tank. Five experimental diets were prepared by providing of 9.8, 43.8, 89.4, 188.5, and 384.2 mg AA equivalent/kg diet, respectively. At the end of the trial, an increasing trend was found on growth performance with the increase of AA supplementation. Fish fed diet supplemented with more than 188.5 mg/kg AA also had significantly higher bone collagen than fish fed diets containing 9.8 mg/kg AA (P < 0.05). According to the broken line, the dietary AA requirement of Caspian brown trout fingerlings was 177.24 mg AA/kg diet based on the weight gain, 186.97 mg AA/kg diet based on the protein tissue, and 163.95 mg AA/kg diet based on the bone collagen. Serum lysozyme and alternative complement pathway activities were also influenced by graded level of AA supplementation to the diet. The present research clearly indicated that AA is required for normal growth and enhancement of immune response in Caspian brown trout fingerlings.     

1,3‐1‐6 ß‐glucans enhance tissue regeneration in zebrafish (Danio rerio): Potential advantages for aquaculture applications

High aquacultural rearing density and handling of fish may frequently result in skin or gills wounds, thereby facilitating the onset of secondary infections. The capacity of the zebrafish to regenerate tissues, as well as fins and other organs, makes it an ideal animal model for studying the mechanisms of tissue regeneration. Since macrophages are involved in tissue regeneration, a diet including ß‐glucans might positively affect the process through activation of macrophages and other immune pathways. Consequently, the aim of this study was to investigate the effects of the oral administration of 1,3‐1,6 β‐glucans on the regeneration process of the caudal fin after its amputation in zebrafish. One hundred and twenty zebrafish were randomly distributed into four groups with three replicates each: an untreated non‐amputated group (CNA) and an untreated amputated group (CA) fed a control diet; two treated and amputated groups (MI and MII) fed for 14 days the same diet with the addition of two differently extracted 1,3‐1,6 ß‐glucans (MacroGard^® and Experimental MacroGard^®, Biorigin^©). ß‐glucans were added to allowed the administration of 12.5 mg/kg of fish body weight (0.35 g/kg of feed). Results showed that 1,3‐1,6 ß‐glucans decreased fish mortality rate and enhanced both daily and cumulative regenerated fin area, independent of the specific ß‐glucan extraction method used. Based on the mechanisms similarities of the innate immune system and tissue regeneration among different teleost species, these results may likely be extended to species of interest for the aquaculture sector.     

Dietary ascorbic acid requirement of cobia,Rachycentron canadum Linneaus

A 10‐week feeding trial was conducted to determine the optimal requirement of cobia (Rachycentron canadum Linneaus) for dietary ascorbic acid (AA). Graded levels of L‐ascorbyl‐2‐polyphosphate (LAPP) were supplemented in basal diet to formulate six semi‐purified diets containing 2.70 (the control diet), 8.47, 28.3, 80.6, 241 and 733 mg AA equivalent kg^?1 diet, respectively. Each diet was randomly fed to triplicate groups of fish in flow‐through plastic tanks (300 L), and each tank was stocked with 25 fish with average initial weight of 4.59 ± 0.36 g. Observed deficiency signs included poor growth, higher mortality and lower feeding rate (FR) in the fish of the control group. Fish fed the control diet had significantly lower weight gain (WG), lower feed efficiency ratio (FER) and lower tissue AA concentrations in fish liver and muscle. With the increase of dietary AA, the survival, WG, FER, hepatic and muscular AA concentrations of cobia significantly increased and then levelled off. The dietary AA requirement of cobia was estimated to be 44.7 mg kg^?1 based on WG, 53.9 mg kg^?1 or 104 mg kg^?1 based on either hepatic or muscular AA concentration, respectively.     

Evaluation of l-ascorbyl-2-glucose as the source of vitamin C for juvenile Korean rockfish Sebastes schlegeli (Hilgendorf)

This study was conducted to compare l ‐ascorbyl‐2‐glucose (AA2G) with l ‐ascorbyl‐2‐monophosphate‐Na/Ca (AMP‐Na/Ca) for supplying the dietary vitamin C for juvenile Korean rockfish Sebastes schlegeli (Hilgendorf). Fish were fed one of seven semi‐purified diets containing equivalents of 0, 50, 100 and 200 mg ascorbic acid (AA) kg^?1 diet in the form of AA2G or AMP‐Na/Ca for 12 weeks. After 12 weeks of feeding, weight gain, feed efficiency ratio and survival of fish fed the vitamin C‐free diet were significantly lower than those of fish fed the vitamin C‐supplemented diets in either form. The hepatosomatic index, condition factor and survival of fish fed AMP‐Na/Ca₁₀₀, AMP‐Na/Ca₂₀₀, AA2G₁₀₀ and AA2G₂₀₀ diets were significantly higher than fish fed the vitamin C‐free diet. After 9 weeks of feeding, fish fed the vitamin C‐free diet began to show vitamin C deficiency signs such as anorexia and lethargy. At the end of the 12‐week feeding trial, fish fed the vitamin C‐free diet exhibited vitamin C deficiency signs, e.g., anorexia, scoliosis, exophthalmia and fin haemorrhage. Vitamin C retention in the muscle and liver was similar to those of fish fed AA2G‐ or AMP‐Na/Ca‐supplemented diets. In general, there was no significant difference in the muscle and liver vitamin C concen‐tration in fish fed the AA2G and AMP‐Na/Ca diets at the same supplementation levels.     

Dietary Vitamin C Requirement of Fingerling,Cirrhinus mrigala (Hamilton), Based on Growth,Feed Conversion,Protein Retention,Hematological Indices,and Liver Vitamin C Concentration

This study was conducted to quantify dietary vitamin C requirement of fingerling, Cirrhinus mrigala, (0.79 ± 0.07 g; 3.51 ± 0.15 cm) by feeding casein‐gelatin based purified diets (400 g/kg crude protein; 3.45 kcal/g digestible energy) containing nine levels of vitamin C as l‐ascorbyl‐2‐polyphosphate (0.0, 5, 15, 25, 35, 45, 55, 75, and 95 mg vitamin C equivalent/kg diet) to triplicate groups of fish to apparent satiation for 16 wk. Absolute weight gain (AWG, g/fish), feed conversion ratio (FCR), protein retention efficiency (PRE%), RNA/DNA ratio, hemoglobin (Hb, g/dL), and hematocrit value (Hct%) were taken as the response criteria to determine vitamin C requirement of mrigal. Fish fed diet with 35 mg/kg vitamin C had significantly higher AWG (9.94 g/fish), FCR (1.39), PRE (27.72%), RNA/DNA ratio (4.18), Hb (11.15 g/dL), and Hct (34.44%) values. However, liver vitamin C concentration was found to be higher (64.92 µg/g wet tissue) in diet containing 45 mg vitamin C/kg. Broken‐line regression analysis of AWG data estimated the requirement of 35.65 mg/kg, whereas that of the liver vitamin C concentration data projected the requirement to 41.99 mg/kg.     

No synergistic effects by the dietary supplementation of ascorbic acid, α-tocopheryl acetate and selenium on the growth performance and challenge test of Edwardsiella tarda in fingerling Nile tilapia, Oreochromis niloticus L.

To investigate the potential synergistic effects of dietary ascorbic acid (AA), α‐tocopheryl acetate (TA) and selenium (Se) supplementation above minimum requirement levels on the growth performance and disease challenge of fingerling Nile tilapia, Oreochromis niloticus L., five experimental diets were formulated: control (150 mg AA, 100 mg TA and 0.2 mg Se per kg diet), excessive ascorbic acid (eAA) (2000 mg AA, 100 mg TA and 0.2 mg Se per kg diet), excessive α‐tocopheryl acetate (eTA) (150 mg AA, 240 mg TA and 0.2 mg Se per kg diet), excessive selenium (eSe) (150 mg AA, 100 mg TA and 0.5 mg Se per kg diet) and excessive all (eALL) (2000 mg AA, 240 mg TA and 0.5 mg Se per kg diet). Experimental fish averaging 2.9 were randomly distributed in each aquarium as a group of 40 fish with total weight 116±2.9 g (mean±SD). Each diet was fed on a dry‐matter basis to fish in three randomly selected aquaria at a rate of 4–8% of total body weight daily. After 10 weeks of the feeding trial, fish fed eAA, eTA and eALL diets had significantly higher weight gain, feed efficiency ratio, protein efficiency ratio and specific growth rate than fish fed eSe and control diets (P<0.05). There was no significant difference among fish fed five experimental diets in cumulative mortalities when fish were challenged with Edwardsiella tarda at the end of the experimental period. These results indicate that sufficient supplementation of dietary AA or TA had positive effects on growth performance, but there was no synergistic effect of excessive dietary AA, TA and Se supplementation on growth performance and disease resistance to E. tarda in fingerling Nile tilapia.     

Alleviation effect of dietary cerium and its complex with chitosan oligosaccharide on cadmium accumulation in juvenile turbot,Scophthalmus maximus L., under cadmium stress

An 8 weeks feeding trial was conducted to investigate the effect of dietary cerium (Ce) and its complex with chitosan oligosaccharide (COS‐Ce) on growth performance and cadmium (Cd) accumulation of turbot, Scophthalmus maximus L. under Cd stress. The basal diet (Diet 0) was formulated without Cd and cerium as the control. Seven other experimental diets (Diets 1–7) were formulated with supplementation of 50 mg Cd²⁺/kg feed, 50 mg Cd²⁺/kg and 50 mg Ce³⁺/kg feed, 50 mg Cd²⁺/kg and 100 mg Ce³⁺/kg feed, 50 mg Cd²⁺/kg and 200 mg Ce³⁺/kg feed, 50 mg Cd²⁺/kg and 50 mg COS‐Ce/kg feed, 50 mg Cd²⁺/kg and 100 mg COS‐Ce/kg feed, and 50 mg Cd²⁺/kg +200 mg COS‐Ce/kg feed. Results of the present study showed that, compared with the control group, the condition factor in fish fed the diet with 50 mg Cd²⁺/kg feed (Diet 1) was significantly lower, whereas the Cd concentration in liver and kidney of fish fed the diet with 50 mg/kg Cd²⁺ (Diet 1) was significantly higher (P < 0.05). The high Cd accumulation of fish fed diets with sole 50 mg/kg Cd (Diet 1) could be significantly decreased by 51.72% after supplementation of 200 mg COS‐Ce/kg in the diet (Diet 7). These results suggested that elevated COS‐Ce could effectively protect against dietary Cd accumulation in turbot.     

Effects of dietary selenium of organic form against lead toxicity on the antioxidant system in Cyprinus carpio

In this study was evaluated potential protective effect of organic selenium (Se) on heavy metal stress induced by lead (Pb) in Cyprinus carpio. For this reason, C. carpio was exposed to sublethal concentration of Pb (1.5 mg/L Pb(NO₃)₂) for 14 days. The fish were fed a basal (control; measured 0.55 mg/kg Se) diet or a basal diet supplemented with 2.50 mg/kg (measured 2.92 mg/kg Se) organic Se (Sel-Plex^®) during the experiment period. The variations in glutathione peroxidase (GSH-Px), glutathione S-transferase (GST) activities, and levels of reduced glutathione (GSH) with malondialdehyde (MDA) in liver and brain tissues of C. carpio were investigated in experimental groups. GSH levels in liver and brain tissues were significantly decreased by exposure to Pb. GST activity was significantly increased (p < 0.05) in liver tissue, but decreased in brain of treated fish by exposure to Pb. Also, GSH-Px activity was significantly increased in liver tissue, but decreased in brain of Pb-treated fish. Levels of MDA were increased in liver and brain of Pb-treated fish. The organic Se treatment for Pb-intoxicated animals improved activities of GSH-Px, GST and levels of MDA within normal limits. Supplemented Se could be able to improve Pb-induced oxidative stress by decreasing lipid peroxidation and regulating antioxidant defense system in tissues.     

Dietary amino acid profile affects muscle cellularity,growth, survival and ammonia excretion of meagre (Argyrosomus regius) larvae

Formulation of diets according to fish amino acid (AA) qualitative requirements may improve fish growth. Two diets with different AA profiles were tested on 16‐day‐old meagre during 20 days. The first diet had an AA profile closer to meagre larval AA requirements (BAL), whereas the second had a different AA profile (UNBAL). Results showed that larvae fed the diet with higher similarities to the AA profile of meagre carcass had a higher final weight (19.8 ± 0.5 mg versus 13.4 ± 1.8 mg) and lower ammonia excretion after being fed (0.6 ± 0.1 ml/(g DW. larvae. h) and 0.8 ± 0.1 ml/(g DW larvae. h)). A higher mean fibre area was obtained in 36 DAH larvae fed the BAL diet (224.8 ± 33.3 μm² versus 158.8 ± 34.5 μm²) as well as higher larval weight. When fibre area distribution was analysed, a higher frequency of larger fibres was observed in 36 DAH BAL larvae, suggesting that fibre hypertrophy had a higher importance in this treatment. In conclusion, this study shows that meagre larvae fed a diet with an AA profile closer to their requirements had lower nitrogen losses and higher final weight, as result of higher muscle hypertrophy.     

Preliminary Study of the Optimum Dietary Ascorbic Acid Level in Sea Cucumber,Apostichopus japonicus (Selenka)

A 14‐wk feeding trial was carried out to evaluate the optimum dietary ascorbic acid (AA) level in juvenile sea cucumber, Apostichopus japonicus. Sea cucumbers averaging 1.49 ± 0.07 g (mean ± SD) were randomly distributed into 18 rectangular plastic tanks of 20 L capacity in a recirculating system (20 animals per tank). Six semipurified experimental diets were formulated to contain 0 (l ‐ascorbyl‐2‐monophosphate [AMP]; AMP0), 30 (AMP24), 60 (AMP48), 120 (AMP100), 240 (AMP206), and 1200 (AMP1045) mg AA/kg diet in the form of AMP using casein as the main protein source. Sea cucumbers were fed each of the six experimental diets in triplicate groups. At the end of 14 wk of feeding trial, weight gain (WG), specific growth rate (SGR), and feed efficiency (FE) of sea cucumbers fed AMP100, AMP206, and AMP1045 were significantly (P < 0.05) higher than those of animals fed AMP0, AMP24, and AMP48. However, there were no significant differences in WG, SGR, and FE among sea cucumbers fed AMP100, AMP206, and AMP1045 and among animals fed AMP0, AMP24, and AMP48. Whole‐body vitamin C concentration increased with AA content of the diets. Broken‐line analysis of WG showed an optimum dietary AA level of 105.3 mg AA/kg diet in sea cucumber. These results indicated that the optimum dietary vitamin C level in sea cucumber in the form of AMP could be greater than 100 mg AA/kg diet but less than 105.3 mg AA/kg diet.     

Replacement of fish meal in juvenile channel catfish,Ictalurus punctatus,diets using a yeast‐derived protein source: the effects on weight gain,food conversion ratio,body composition and survival of catfish challenged with Edwardsiella ictaluri

We examined the effects of a yeast‐derived protein source (NuPro^®) as a replacement for menhaden fish meal on weight gain, specific growth rate (SGR), food conversion ratio (FCR), whole‐body composition and disease resistance in juvenile channel catfish (9.9 ± 0.2 g fish^?1). NuPro^® replaced fish meal at six levels (0, 25, 50, 75, 100 and 125 g kg^?1 diet). Catfish were sampled for whole‐body composition and then challenged with the bacterium Edwardsiella ictaluri. Growth performance was negatively affected (P < 0.01) when NuPro^® was added at 125 g kg^?1 diet. The amount of whole‐body fat decreased (P < 0.05) when NuPro^® was added at 75 g kg^?1 or more of the diet. Regardless of the amount of NuPro^® added, survival after challenge with E. ictaluri was similar among treatments. Results indicate that up to 100 g kg^?1 of NuPro^® can be added without negatively affecting growth performance. The yeast‐derived protein source used in this study is a sustainable protein alternative that could be used as a partial replacement for fish meal in juvenile channel catfish diets.     

An attempt to improve the reproductive efficiency of Nile tilapia brood stock fish

A field study was conducted on brood stock Nile tilapia to increase the propagation. Both sexes were individually stocked into Habas (enclosures) in an earthen pond and fed for 19 days on a basal diet supplemented with different additives at graded levels of each (0.5, 1.0 and 2.0 g Therigon^®; 1.0, 2.0, and 3.0 g Nuvisol Hatch P^®; 20, 40 and 60 mg Gibberellic acid and 700, 900 and 1,100 mg L-carnitine/Kg diet). The obtained results were evaluated, and the best treatment for each sex was chosen for mating. Results indicated that all pretreatments for male and female brood stocks of Nile tilapia positively affected the total count of the offspring produced. Yet, the Haba, in which the females were pretreated with 0.5 g Therigon^®/Kg diet and the males pretreated with 700 mg L-carnitine/Kg diet, gave the highest total count of the offspring comparing with the other Habas. But, because of the high feed cost due to the additives cost, 0.5 g Therigon^®/kg diet as pretreatment for ♀ only (3rd Haba), 2 g Nuvisol Hatch P^®/Kg diet as pretreatment for ♀ only (5th Haba), followed by 0.5 g Therigon^® and 700 mg L-carnitine/Kg diet for ♀ and ♂, respectively (4th Haba), respectively were the best economically.     

Antioxidant effect of dietary tocopherol and ascorbic acid on growth and survival of Litopenaeus vannamei postlarvae

The nutritional effect of vitamin E in dietsfor Litopenaeus vannamei postlarve (PL19)was investigated. Four formulated diets withdifferent combinations of α-tocopherylacetate (α-TA), ascorbic acid (AA) andhighly unsaturated fatty acids (HUFA) weretested, using four replicates. No significant differences in survival wereobserved among treatments after 34 days offeeding. However, shrimp fed with a dietcontaining 2% fish oil (low n-3 HUFA content),200 mg.kg^?1 α-TA and100 mg.kg^?1 AA (diet H/E/C) showedsignificantly better growth than those fed adiet supplemented with 5% fish oil (high n-3HUFA content), 200 mg.kg^?1 α-TA and100 mg.kg^?1 AA (diet H+/E/C). Shrimp fedwith a diet containing 5% fish oil,900 mg.kg^?1 α-TA and100 mg.kg^?1 AA (diet H+/E+/C) showed a significantly higher tissue level of n-6 PUFAthan postlarvae fed diet H+/E/C. No definiteconclusion could be drawn about a possibleinteraction between α-TA and AA, since acomparison of the diet containing 5% fish oil,200 mg.kg^?1 α-TA and700 mg.kg^?1 AA (H+/E+/C+) and the dietH+/E/C did not show any significant differencesin any of the measured parameters. Theantioxidative status of the shrimp tissue(measured by means of the thiobarbituric acid(TBA) assay and expressed as nM malonaldehyde(MA) per gramme dry weight) was equal for alltreatments. Nevertheless, there was a slightlylower MA value with the diet H+/E/C+,indicating that AA may be an effectiveantioxidant in the aqueous phase and at thewater/lipid interface of the tissue. The tissuelevels of α-T and AA were highlydependent on the amounts in diets and nocorrelation between α-T and AAincorporation could be observed.     

Dietary ascorbic acid requirement of juvenile ayu (Plecoglossus altivelis)

To investigate dietary ascorbic acid (AA) requirement of juvenile ayu (Plecoglossus altivelis) weighing 1.27 ± 0.02 g, eight diets were formulated with graded levels (0, 20, 40, 80, 160, 320, 640 and 1280 mg AA kg^?1) of AA supplied as ascorbyl polyphosphate. Each experimental diet was fed to four‐replicate groups to apparent satiation three times a day for 8 weeks. At the end of the feeding trial, fish fed AA‐deficient diet showed visible AA deficiency signs and low survival. Based on the four‐parameter saturation kinetics model, the calculated AA requirement levels for each dose‐dependent response [weight gain, hepatic AA concentration, hydroxyproline (HyPro) concentration in skin and HyPro concentration in backbone] were 116, 226, 47 and 35 mg kg^?1, respectively. Based on the maximal growth performance, a level of 116 mg AA kg^?1 was recommended for commercial diet of juvenile ayu. To maintain tissue HyPro saturation and avoid AA deficiency symptoms, the minimum required dietary AA level was 47 mg kg^?1. Hepatic AA saturation was considered as the most stringent criterion for determination of AA requirement.     

Evaluation of the Ability of GroBiotic®‐A to Enhance Growth,Muscle Composition,Immune Responses,and Resistance Against Aeromonas hydrophila in Nile tilapia,Oreochromis niloticus

This study was conducted to evaluate the potential of graded levels of GroBiotic^®‐A to improve performance of Nile tilapia, Oreochromis niloticus, fed a 29% crude protein (CP) diet. A 29% CP diet was formulated and supplemented with 0, 0.4, 0.8, and 1.2% GroBiotic^®‐A and compared to performance of fish fed a 33% CP diet. Enhanced weight gain and feed efficiency were generally observed in fish fed the diets supplemented with GroBiotic^®‐A compared to the 29% CP diet. No significant differences in these responses were observed between fish fed diets supplemented with GroBiotic^®‐A compared to those fed the 33% CP diet. Supplementation of 0.8 and 1.2% GroBiotic^®‐A induced significantly lower condition factor and hepatosomatic index compared to fish fed the 29% CP diet, but those values were similar to that of fish fed the 33% CP diet. GroBiotic^®‐A supplementation and protein reduction had no effect on the viscerosomatic index of fish or moisture, lipid, and protein content of muscle samples. However, muscle ash increased significantly with protein reduction (29% CP diet), but GroBiotic^®‐A supplementation (0.8 and 1.2%) reduced muscle ash content. Activities of catalase and superoxide dismutase were markedly reduced in fish fed GroBiotic^®‐A (0.8 and 1.2%) compared to those fed the control diet. GroBiotic^®‐A supplementation also induced significantly higher neutrophil oxidative radical production compared to fish fed the 29% CP diet, but no significant difference was observed in comparison with the 33% CP diet. After 8 wk of feeding, exposure to Aeromonas hydrophila for 3 wk resulted in 40% (0.4, 0.8% GroBiotic^®‐A) and 27% (1.2% GroBiotic^®‐A) mortality and reduced signs of disease, while 47% mortality was observed in fish fed the 29% CP diet. Based on the result of this study, it is concluded that 0.8 and 1.2% GroBiotic^®‐A positively influenced growth performance and feed efficiency of tilapia fed diets containing 29% crude protein to levels comparable to fish fed the 33% CP diet. GroBiotic^®‐A supplementation also significantly increased neutrophil oxidative radical production as well as resistance to Ae. hydrophila infection.     

The effect of dietary protein replacement by crystalline amino acid on growth and nitrogen utilization of turbot Scophthalmus maximus juveniles

A study was conducted to evaluate the effect of partial replacement of dietary fish meal by crystalline amino acids on growth performance, feed utilization, body composition and nitrogen utilization of turbot juveniles.

Four diets were formulated to be isolipidic (12% DM) and isonitrogenous (8% DM). A fish meal based diet was used as control. In the experimental diets, a crystalline amino acid (AA) mixture was used to partially replace fish meal, corresponding to a non-protein nitrogen content of 19, 37 and 56%, respectively (diets 19AA, 37AA and 56AA, respectively). The overall amino acid profile of the experimental diets resembled that of the whole-body protein of turbot. Each experimental diet was fed to triplicate groups of 20 fish (initial body weight of 31.8 g) twice daily to apparent satiation for 42 days. During the trial water temperature averaged 18 °C.

Final body weight, weight gain (g kg ABW^− 1 day^− 1) and specific growth rate were not different between the control and 19AA diet but significantly decreased with the increase of crystalline-AA inclusion from 19 to 56%. Feed intake and feed efficiency of fish fed the control and diet 19AA were similar and significantly higher than those of fish fed the 56AA diet. At the end of the growth trial, there were no significant differences in whole-body composition among groups. Hepatosomatic index was also unaffected by dietary treatments.

Nitrogen retention (g kg ABW^− 1 day^− 1) of fish fed the control and the 19AA diets were similar and significantly higher than that of fish fed the other diets. Expressed as a percentage of the nitrogen intake, N retention was significantly higher with the control than with the 37AA and 56AA diets.

Daily ammonia excretion (mg kg ABW^− 1 day^− 1) of fish fed the control diet was significantly higher than that of fish fed the 37AA and 56AA diets, while daily urea excretion (mg kg ABW^− 1 day^− 1) did not significantly differ among treatments. Non-fecal nitrogen (ammonia + urea) excretion (mg kg ABW^− 1 day^− 1) was significantly higher for fish fed the control diet than in those fed the 37AA and 56AA diets. However, as percent of N intake, ammonia excretion and non-fecal N excretion were significantly higher in fish fed the 56AA diet than in those fed the control and 19AA diets.

Specific activity of glutamate dehydrogenase, alanine and aspartate aminotransferases did not significantly differ among experimental groups.

In conclusion, in diets with an overall amino acid profile resembling that of the whole-body protein of turbot, crystalline-AA may replace 19% of dietary protein without negatively affecting growth performances or feed utilization efficiency. However, higher protein replacement levels of protein-bound-AA by crystalline-AA severely depressed growth performance.     

Enhancement of Hsp70 synthesis protects common carp, Cyprinus carpio L., against lethal ammonia toxicity

Exposure to TEX‐OE^®, a patented extract of the prickly pear cactus (Opuntia ficus indica) containing chaperone‐stimulating factor, was shown to protect common carp, Cyprinus carpio L., fingerlings against acute ammonia stress. Survival was enhanced twofold from 50% to 95% after exposure to 5.92 mg L^?1 NH₃, a level determined in the ammonia challenge bioassay as the 1‐h LD50 concentration for this species. Survival of TEX‐OE^®‐pre‐exposed fish was enhanced by 20% over non‐exposed controls during lethal ammonia challenge (14.21 mg L^?1 NH₃). Increase in the levels of gill and muscle Hsp70 was evident in TEX‐OE^®‐pre‐exposed fish but not in the unexposed controls, indicating that application of TEX‐OE^® accelerated carp endogenous Hsp70 synthesis during ammonia perturbation. Protection against ammonia was correlated with Hsp70 accretion.