Vitamin C requirement of kuruma shrimp postlarvae, Marsupenaeus japonicus (Bate), using l-ascorbyl-2-monophosphate-Na/Ca

l ‐ascorbyl‐2‐monophosphate‐Na/Ca (AMP‐Na/Ca) was used as a vitamin C source to investigate the ascorbic acid (AsA) requirements on growth performance and stress resistance of the post‐larval kuruma shrimp, Marsupenaeus japonicus. Purified carrageenan‐microbound diets with six levels of AMP‐Na/Ca, AsA equivalent to 0, 20, 56, 87, 759 and 1697 mg kg^?1 diet were fed to triplicate groups of M. japonicus (mean initial weight 16±0.3 mg) for 30 days. The diets with AsA 0, 20 and 56 mg kg^?1 showed high cumulative mortality after 10 days of feeding. After the 30‐day trial, the shrimp fed these diets had significantly lower survival and weight gain (WG, %) than those fed the 87, 759 and 1697 mg AsA kg^?1 diets. Specific growth rate and individual dry weight showed the same pattern as WG (%). There were no significant differences in growth performance among the groups fed the AsA levels at 87, 759 and 1697 mg kg^?1 at the termination of feeding trial. Broken‐line regression analysis indicated that 91.8 mg AsA kg^?1 in the diet was the optimum for post‐larval shrimp. On the other hand, dietary level of more than 800 mg AsA kg^?1 was needed to ensure high resistance to stressful conditions such as osmotic and formalin stressors.     

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.     

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 Vitamin C on Blood Chemistry and Nonspecific Immune Response of Juvenile Red Sea Bream,Pagrus major

A trial was conducted to determine the effect of ascorbyl‐2‐monophosphate Na/Ca (AMP‐Na/Ca) on blood chemistry and nonspecific immune response of red sea bream juveniles. Test diets with three levels of AsA (free, 107, and 325 mg/kg diet) were fed to juvenile red sea bream (36.0 ± 1.3 g) two times a day for 3 wk. There were no significant differences in hematocrit, glucose, and blood urea nitrogen. Total cholesterol and triglyceride in plasma of fish fed AsA‐free diet was significantly (P < 0.05) higher than that of fish fed two other diets. There were no significant differences in serum albumin, total bilirubin, and total serum protein. Glutamyl oxaloacetic transaminase in serum of fish fed diets containing 107 and 325 mg of AsA were significantly (P < 0.05) lower than that of fish fed AsA‐free diet. Serum lysozyme activity (LA) of fish fed diets containing 107 and 325 mg of AsA were significantly (P < 0.05) higher than that of fish fed AsA‐free diet. There was no significant difference in mucus LA. The results mentioned above demonstrated that AMP‐Na/Ca is a bioavailable AsA source for red sea bream juveniles. Supplement of more than 107 mg AsA/kg in diets improved blood chemistry and nonspecific immune function of red sea bream juveniles.     

Effectiveness of l‐ascorbyl‐2‐polyphosphate as an ascorbic acid source for sea cucumber,Apostichopus japonicus

A feeding trial was conducted to determine the adequate dietary ascorbic acid (AsA) levels and the effects on growth, meat quality and antioxidant status of sea cucumber (10.04 ± 0.06 g), Apostichopus japonicus. l ‐ascorbyl‐2‐polyphosphate (35% AsA equivalent) was supplemented separately to the basal diet to obtain five AsA levels, 0, 598, 1473, 4676 and 14340 mg kg^?1 diet respectively. After 60‐day feeding trial, the sea cucumbers fed diets containing 598 and 1473 mg AsA kg^?1 showed significantly higher (P < 0.05) body weight gain and specific growth rate values than the sea cucumbers fed control diets. The sea cucumbers fed diets containing 1473 and 4676 mg AsA kg^?1 showed significantly higher (P < 0.05) hydroxyproline contents than those of the sea cucumbers fed diets containing 0 and 598 mg AsA kg^?1. Antioxidant enzymes such as total antioxidant capacity, superoxide dismutase and glutathione peroxidase showed increasing trends with the increasing dietary AsA levels, but no significant differences (P > 0.05) were observed when the sea cucumbers fed diets with high dietary AsA levels. The content of malondialdehyde had the opposite trend of antioxidant enzymes. In conclusion, the adequate dietary AsA level focusing on growth performance of sea cucumber is between 598 and 1473 mg kg^?1 diet. Furthermore, high level of dietary AsA (between 598 and 4676 mg kg^?1 diet) improved meat quality and antioxidant status.     

Effect of l‐ascorbyl‐2‐polyphosphate supplementation on growth performance,body composition,antioxidative capacity and salinity stress tolerance of juvenile Pacific white shrimp,Litopenaeus vannamei

An 8‐week feeding trial was conducted to evaluate the effects of ascorbic acid (AsA), in the form of l ‐ascorbyl‐2‐polyphosphate (LAPP) on growth performance, body composition, antioxidative capacity and salinity stress tolerance of juvenile Pacific white shrimp, Litopenaeus vannamei. Five practical diets (46% crude protein and 7.6% lipid) supplemented with graded levels of AsA (14.64, 48.55, 84.98, 308.36 and 639.27 mg kg^?1 diet) were fed to five replicate groups of L. vannamei (mean initial wet weight 0.57 g). No significant differences were found on growth performance among all treatments. However, whole body lipid content significantly decreased with dietary AsA levels increasing. Activities of total antioxidant capacity, glutathione reductase and glutathione peroxidase were significantly affected by dietary AsA levels. Shrimp fed LAPP‐free diet had higher malondialdehyde content than those fed the diets supplemented with LAPP. Dietary AsA levels higher than 308.36 mg kg^?1 diet increased the survival of shrimps after 1, 2 and 3 h of acute salinity change. Broken‐line regression analysis on survival after 3 h of salinity stress and second‐degree polynomial regression analysis on glutathione reductase data indicated that the optimal dietary AsA requirement of L. vannamei was estimated to be 306.39, 319.75 mg kg^?1 diet respectively.     

Interactive effects of dietary vitamin C and phospholipid in micro‐bound diet for growth,survival, and stress resistance of larval red sea bream,Pagrus major

This study was conducted to examine the effects of dietary ascorbic acid (AsA) and phospholipid (PL) and their interaction on growth, survival, and stress resistance in red sea bream larvae. Twenty‐six days old red sea bream were fed nine micro‐bound diets supplemented three levels of AsA (0, 800 and 1600 mg kg^?1 diet) and PL (0, 20 and 40 g kg^?1 diet) for 15 days. Dietary AsA and PL were both significant factors on survival rates. There was also an interaction between dietary AsA and PL on survival rate (P < 0.05). The larvae fed 800 or 1600 mg kg^?1 AsA with 40 g kg^?1 PL diets showed the highest survival rate, with values similar to those of the live‐food supplemented group. Stress resistance against low salinity exposure significantly increased with increased dietary level of AsA and PL. However, significant interaction of AsA and PL was not detected. The larvae fed 1600 mg kg^?1 AsA with 40 g kg^?1 PL diet showed the highest stress resistance among all diets, but it was not significantly different than that of larvae fed 800 mg kg^?1 AsA with 40 g kg^?1 PL diet. This study clearly demonstrated that combined use of AsA and PL can improve survival of 26–40 days posthatching red sea bream larvae. Moreover, the present study suggested that 800 mg kg^?1 AsA with 40 g kg^?1 PL in diet was needed for producing high quality seedling under the stressful conditions.     

The effects of dietary vitamin C on growth performance,serum enzymes activities and resistance to Vibrio alginolyticus challenge of yellow drum Nibea albiflora

A 9‐week feeding trial was conducted to determine the optimal dietary vitamin C requirement and its effects on serum enzymes activities and bacterial resistance in the juvenile yellow drum Nibea albiflora (initial weight 33.2 ± 0.10 g). Six practical diets were formulated containing vitamin C 2.1, 45.3, 89.6, 132.4, 178.6 and 547.1 mg kg^?1 diet supplied as l ‐ascorbyl‐2‐monophosphate. The fish fed 547.1 mg kg^?1 diet showed a significantly higher survival than that fed 2.1 mg kg^?1 diet. The weight gains and specific growth rate of the fish fed 2.1 mg kg^?1 diet were significantly lower than those of the fish fed 89.6–547.1 mg kg^?1 diets. The liver vitamin C concentration firstly increased with increasing dietary vitamin C supply from 2.1 to 178.6 mg kg^?1 diet and then stabilized. The serum superoxide dismutase activities of the fish fed 547.1 mg kg^?1 diet were significantly lower than those of the fish fed 2.1–89.6 mg kg^?1 diet. The fish fed 2.1 mg kg^?1 diet had a significantly higher alkaline phosphatase activity than those in the other groups except the 45.3 mg kg^?1 group. Fish that received diets containing vitamin C at 547.1 mg kg^?1 had significantly higher nitro blue tetrazolium and lysozyme activity, and fish that received diets containing vitamin C at 45.3–547.1 mg kg^?1 exhibited resistance against Vibrio alginolyticus infection. The dietary vitamin C requirement of the juvenile yellow drum was established based on broken‐line model of weight gain to be 142.2 mg l ‐ascorbyl‐2‐monophosphate kg^?1 diet.     

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.     

Dietary nucleotide supplementation enhances growth and immune responses of grouper,Epinephelus malabaricus

Basal diet containing 0.5, 1.0, 1.5 and 2.0 g kg^?1 mixture of inosine monophosphate (IMP), adenosine monophosphate (AMP), guanosine monophosphate (GMP), uridine monophosphate (UMP) and cytidine monophosphate (CMP) (1 : 1 : 1 : 1 : 1) (mixed‐NT; Experiment 1) and 1.5 g kg^?1 from each nucleotides and mixed‐nucleotides (NT; Experiment 2) were fed to triplicate groups of grouper for 8 weeks. Basal diet without NT was used as control in both Experiments. In Experiment 1, fish fed the diet with 1.5 g mixed‐NT kg^?1 had higher (P < 0.05) weight gain (WG) than the control group. The superoxide anion (O₂^?) production ratio was higher in fish fed diets with 1.0–1.5 g mixed‐NT kg^?1 than the fish fed diets with ≤0.5 g mixed‐NT kg^?1. In Experiment 2, fish fed diets with nucleotides had higher WG than the control group. The O₂^? production ratio was higher in fish fed the diet with 1.5 g AMP kg^?1, followed by fish fed diets with 1.5 g UMP and mixed‐NT kg^?1, and lowest in the control group. These results suggest that growth and immune responses were enhanced in grouper fed diet with 1.5 g mixed‐NT kg^?1 diet. Diet with 1.5 g kg^?1 of AMP seems to be more beneficial on the immune responses in fish than other nucleotides.     

Use of marine by‐product meals in diets for juvenile longfin yellowtail Seriola rivoliana

A 60‐day feeding trial to determine the nutritional value of marine by‐product meals in diets for longfin yellowtail Seriola rivoliana juveniles (48.1 ± 0.6 g initial weight) was conducted. Five diets were evaluated: a reference diet (RD; 500 g kg^?1 CP, 130 g kg^?1 L), containing 500 g kg^?1 of fish meal (FM); three experimental diets with 125 g kg^?1 of shrimp head (SM), Catarina scallop viscera (CM) or Pen shell viscera (PM) meals; and one diet (SCP) containing 125 g kg^?1 of each of the experimental meals, to partially replace FM. Survival was not significantly affected by any treatment. Individual weight gain per day was high for the PM (5.3 ± 0.51 g d^?1) and SM (4.7 ± 0.32 g d^?1) diets, being significantly higher than the RD (3.5 ± 0.23 g d^?1) and the other treatments (<1.2 g d^?1). Feed intake was high in PM and SM diets, and very low in SCP and CM diets. Biochemical and haematological parameters were similar among treatments RD, PM and SM, while fish fed CM and SCP exhibited lower levels of total protein, cholesterol, haematocrit and haemoglobin. The results indicate that SM or PM can be used to partially replace FM in diets for yellowtail juveniles.     

Dietary myo‐inositol requirement for juvenile gibel carp (Carassius auratus gibelio)

An 11‐week growth trial was conducted to determine dietary myo‐inositol (MI) requirement for juvenile gibel carp (Carassius auratus gibelio). Myo‐inositol was supplemented to the basal diet to formulate six purified diets containing 1, 56, 107, 146, 194 and 247 mg MI kg^?1 diet, respectively. Each diet was fed to triplicate groups of juvenile gibel carp (initial body weight 3.38 ± 0.27 g, mean ± SD) in a flow‐through system. The diets were randomly assigned to different fish tanks. Fish fed ≥ 107 mg MI kg^?1 diet had significantly higher weight gain (WG), feed efficiency (FE) and protein efficiency ratio than those fed 1 mg MI kg^?1 diet. Fish fed ≥ 56 mg MI kg^?1 diet had higher feeding rate and survival compared with fish fed 1 mg MI kg^?1 diet. Dietary supplemental inositol did not affect fish liver inositol concentration. Fish fed ≥ 56 mg MI kg^?1 diet had higher body dry matter, crude protein and gross energy and lower hepatosomatic index than fish fed 1 mg MI kg^?1 diet. Dietary inositol supplementation decreased fish body ash. Quadratic regression of weight gain indicated that the myo‐inositol requirement to maximum growth for juvenile gibel carp was 165.3 mg MI kg^?1 diet.     

Dietary calcium requirements of juvenile tilapia, Oreochromis niloticus × O. aureus, reared in fresh water

A feeding experiment was conducted to determine the dietary calcium (Ca) requirement for juvenile hybrid tilapia, Oreochromis niloticus × O. aureus reared in nature water. Purified diet supplemented with 0, 1, 2, 3, 4, 5, 7 and 10 g Ca kg⁻¹ diet providing of 0.6, 1.6, 2.6, 3.7, 4.7, 5.5, 7.5 and 10.7 g Ca kg⁻¹ diet, respectively, were fed to tilapia (mean initial weight: 0.52 ± 0.01 g, n = 3) for 8 weeks. Each diet was fed to three replicate groups of fish in a closed, recirculating fresh water rearing system. The rearing water contained 27.1–33.3 mg L⁻¹ Ca. The tilapia fed the diets supplemented with ≥3.7 g Ca kg⁻¹ had significantly (P < 0.05) higher weight gain, when compared with fish fed the diet with ≤1.6 g Ca kg⁻¹. Fish fed the unsupplemented control showed significantly lower weight gain when compared with the other groups (P < 0.05). Bone Ca concentration was highest in fish fed the diets with ≥4.7 g Ca kg⁻¹, intermediate in fish fed the diet with 2.6 g Ca kg⁻¹ and lowest in fish fed the control diet. Scale Ca concentration was higher in fish fed the diets with ≥3.7 g Ca kg⁻¹ than in fish fed the diets with ≤2.6 g Ca kg⁻¹. Serum alkaline phosphatase activity was 36% increased in fish fed the diets with ≥2.6 g Ca kg⁻¹ than fish fed the diets with <1.6 g Ca kg⁻¹. Analysis by broken‐line regression of weight gain, bone and scale Ca concentrations indicated that the adequate dietary Ca concentration for tilapia in water containing 27.1–33.3 mg Ca L⁻¹ was 3.5, 4.3 and 4.2 g Ca kg⁻¹ diet, respectively, supplied as Ca‐lactate.     

Effects of dietary protein and lipid levels on growth,feed utilization and body composition in red‐tailed catfish juveniles (Hemibagrus wyckioides,Chaux & Fang 1949)

A feeding trial was conducted in a recycling water system during 10 weeks to determine the optimal protein to lipid ratio in Asian red‐tailed catfish (Hemibagrus wyckioides). Six diets of two protein levels (390 and 440 g kg^?1) with three lipid levels (60, 90 and 120 g kg^?1) were formulated. Fish (1.96 g) were fed six diets with four replicates to apparent satiation at a stocking density of 50 fish per tank (500 L). Faeces were collected in cultured tanks at the end of the feeding trial for digestibility measurement. Significantly, improved growth performances (P < 0.01) and higher feed utilization (P < 0.001) were observed in fish fed with higher lipid diets. However, higher protein diets did not significantly improve fish growth but they reduced FCR (P < 0.001) and protein efficiency ratio (P < 0.01). Higher lipid diets also resulted in significantly increased adipose‐somatic index, carcass fat and reduced moisture of the fish. The study revealed the protein sparing effect of dietary lipid in the catfish and highest growth performance was found by fish fed 390 g kg^?1 protein and 120 g kg^?1 lipid diet with P/E ratio of 20.48 mg protein kJ^?1. DP/DE ratio for maximal growth rate in diets was 21.48 mg protein kJ^?1.     

The effects of dietary lipid levels on performance and heat‐shock protein response of juvenile white seabass,Atractoscion nobilis

A feeding trial was conducted to study the effect of dietary lipid on growth performance and heat‐shock protein (HSP70 and HSP60) response of white seabass (WSB), Atractoscion nobilis. Five diets were formulated to contain 440 g kg^?1 protein from 300 g kg^?1 fish meal, 240 g kg^?1 soybean meal and 100 g kg^?1 soy protein concentrate with different levels of lipid: 100, 120, 140, 160 or 180 g kg^?1. At the end of the trial, heat shock response based on HSP70 and HSP60 was measured in liver and white muscle from fish at ambient temperature and temperature shock conditions. Final weight and percent gain were significantly higher for fish fed the 100 g kg^?1 lipid diet than for fish fed the rest of the diets (P ≤ 0.05). Feed conversion ratio was lowest for fish fed the 100 g kg^?1 lipid diet. The HSP70 and HSP60 responses were positively correlated to dietary lipid levels following temperature shock. At ambient temperature, HSP60 and HSP70 responses in muscle and HSP60 response in liver increased with dietary lipid level. Temperature shock significantly increased the HSP response of fish in all treatments. Results of this study demonstrated that a moderate (110–120 g kg^?1) level of dietary lipids would be recommended for production diets but a higher dietary lipid level may be required for optimal stress tolerance.     

Histologic changes in channel catfish,Ictalurus punctatus Rafinesque,fed diets containing graded levels of gossypol–acetic acid

A study was performed to evaluate the histologic changes among fingerling channel catfish, Ictalurus punctatus Rafinesque, fed purified diets containing gossypol from gossypol–acetic acid. The catfish were maintained on diets with 0, 300, 600, 900, 1200 or 1500 mg gossypol kg^?1 diet for 12 weeks, and histologic samples from the stomach, proximal and distal intestines, pancreas, liver, and spleen were obtained from fish in all groups. Stomach sections exhibited significant gastric gland necrosis in fish fed 600 mg gossypol kg^?1 diet or higher. Non‐existent‐to‐mild enterocyte vacuolization loss, inflammatory cell infiltration, and hyperplastic lamina propria were noted in the intestinal sections from gossypol‐fed fish, but no significant differences in severity scores were noted. The pancreas from fish fed doses of gossypol above 600 mg gossypol kg^?1 diet exhibited significant mild‐to‐severe necrosis, and livers from fish fed 900 and 1500 mg gossypol kg^?1 diet exhibited significantly higher pigment deposition. No other significant histologic differences were observed in the fish fed diets containing gossypol–acetic acid. The data in this study indicates that at least 600–900 mg gossypol kg^?1 purified diet can cause statistically significant histologic changes in fingerling channel catfish, suggesting that gossypol should remain at concentrations below 600 mg gossypol kg^?1 diet.     

Interactive effects of dietary magnesium and vitamin E on growth performance,body composition,blood parameters and antioxidant status in Japanese seabass (Lateolabrax japonicus) fed oxidized oil

A study was conducted to investigate effects and interactions of magnesium (Mg) and vitamin E (VE) on growth performance, body composition, hepatic antioxidant capacity and serum biochemistry parameters of juvenile Japanese seabass Lateolabrax japonicus under oxidative stress condition. Fish (initial average body weight of 6.10 ± 0.20 g) were fed 9 oxidized oil diets supplemented with 3 grade levels of Mg (0, 520 and 1570 mg kg^?1 diet) and VE (0, 60 and 200 mg kg^?1 diet) for 8 weeks in freshwater. The results showed that diets supplemented 520 mg kg^?1 Mg and/or 60 mg kg^?1 VE had highest growth and muscle lipid content. There were highest total superoxide dismutase, catalase, glutathione peroxidase activities and lowest malondialdehyde content in liver of fish fed diets supplemented 520 mg kg^?1 Mg and/or 60 mg kg^?1 VE. Contrary to Mg concentrations, Ca concentrations and Ca/Mg ratio in whole body were inversely related to dietary Mg levels. However, combined deficiency or excess of dietary Mg and VE led to the decrease of hepatic antioxidant capacity, body lipid deposition and growth of Japanese seabass under oxidative stress condition.     

Dietary biotin requirement for growth of juvenile zebrafish Danio rerio (Hamilton‐Buchanan)

This study was conducted to estimate the dietary biotin requirement for maximum growth of zebrafish Danio rerio. Six isonitrogenous and isocaloric purified diets containing 0.031 (biotin‐unsupplemented diet), 0.061, 0.263, 0.514, 1.741 and 2.640 mg biotin kg^?1 diet were fed in triplicate tanks for a total of 12 weeks to juvenile zebrafish (initial mean body mass 0.13 ± 0.001 g). From 4 weeks of feeding, fish fed diets with ≤0.061 mg biotin kg^?1 showed biotin deficiency signs, such as retarded growth and skeletal deformity, was observed on some dead fish. At the end of the study, gill disorders were observed on some fish and liver glycogen accumulation were also observed in fish fed these diets. Fish fed the biotin‐unsupplemented diet exhibited a lower final body weight, protein efficiency ratio and feed utilization than the fish fed the biotin‐supplemented diets, whereas the highest values were observed with the diet containing 0.51 mg biotin kg^?1 diet (P < 0.05). A linear relationship (r² = 0.77; P < 0.0001) was observed between whole‐body biotin content and dietary biotin level. A broken‐line analysis indicated that the optimum dietary biotin content for maximal growth expressed as final body weight is 0.51 mg kg^?1 diet.     

Dietary vitamin E could improve growth performance,lipid peroxidation and non‐specific immune responses for juvenile cobia (Rachycentron canadum)

An 8‐week feeding trial was conducted to establish the dietary vitamin E requirement of juvenile cobia. The basal diet was supplemented with 10, 20, 30, 40, 60, 120 mg vitamin E kg^?1 as all‐rac‐α‐tocopheryl acetate. The results indicated that fish fed the diets supplemented vitamin E had significantly higher specific growth rate, protein efficiency ratio, feed efficiency and survival rate than those fed the basal diet. It was further observed that vitamin E concentrations in liver increased significantly when the dietary vitamin E level increased from 13.2 to 124 mg kg^?1. Fish fed the basal diet had significantly higher thiobarbituric acid‐reactive substances concentrations in liver than those fed the diets supplemented vitamin E. Fish fed the diets supplemented with 45.7 and 61.2 mg kg^?1 vitamin E had significantly higher red blood cell and haemoglobin than those fed the basal diet, while fish fed the diets supplemented with 61.2 and 124 mg kg^?1 vitamin E had higher immunoglobulin concentration than those fish fed the basal diet. Lysozyme and superoxide dismutase were significantly influenced by the dietary vitamin E level. The dietary vitamin E requirement of juvenile cobia was established based on second‐order polynomial regression of weight gain and lysozyme to be 78 or 111 mg all‐rac‐α‐tocopheryl acetate kg^?1 diet, respectively.     

Effects of vitamin C inclusion in practical diets on survival and growth of juvenile crayfish (Pacifastacus leniusculus Dana,Astacidae) from the onset of exogenous feeding

The aim of this study was to evaluate the effects of practical diets with different levels of vitamin C on survival and growth of juvenile crayfish (Pacifastacus leniusculus). An 80‐day trial was conducted with stage 2 juveniles from the onset of exogenous feeding. Four practical diets differing in the content of l ‐ascorbyl‐2‐monophosphate‐Na were prepared: 0, 0.2, 0.4 or 0.8 g kg^?1 diet. Each diet was tested on grouped or individually isolated crayfish. Diets had no significant effects on survival of crayfish held in groups (average: 73.1%) neither on the isolated ones (average: 90%). Crayfish fed the diet with 0.2 g kg^?1 of l ‐ascorbyl‐2‐monophosphate‐Na had the highest growth (groups: 13.64 mm carapace length (CL), 542.4 mg weight; isolated: 17.05 mm CL, 1213.2 mg weight) and the lowest feed conversion ratio (average of grouped and isolated: 0.99). This study provides the first data on vitamin C requirements of freshwater crayfish. A level of 0.2 g l ‐ascorbyl‐2‐monophosphate‐Na kg^?1 diet (0.07 g ascorbic acid equivalent) can be recommended for juvenile P. leniusculus during the first period of intensive rearing.