Growth Response of Nile Tilapia Oreochromis niloticus to Dietary L-Ascorbic Acid, L-Ascorbyl-2-Sulfate, and L-Ascorbyl-2-Polyphosphate

Abstract.— Purified diets were formulated and fed to seven groups of Nile tilapia Oreochromis niloricus fingerlings for 12 weeks. Six of the formulated diets contained 5 or 50 mg/kg of ascorbic acid equivalent supplied either by L-ascorbic acid (AA), L-ascorbyl-2-sulfate (AS) or L-ascorbyl-2-polyphosphate (APP). The seventh basal diet was ascorbate-free and served as the control. The study indicated that APP or AS was more effectively utilized as a source of vitamin C than equimolar AA in promoting growth, improving food conversion, and preventing scurvy in Nile tilapia. Fish fed the ascorbate-free diet and the diet containing 5 mg AA/kg exhibited external signs of scurvy at 10 weeks. Diets containing 5 mg/kg of ascorbic acid from AS or APP provided some growth with no overt signs of scurvy indicating that this concentration of AS and APP might be near the minimum requirements for the species. The best growth, food conversion ratio, survival rate, and ascorbic acid content in liver were obtained with the diet containing 50 mg ascorbate equivalent/kg diet from APP followed by the diet containing 50 mg ascorbate equivalent/kg diet from AS. Fish fed diets with 50 mg ascorbic acidkg diet from AS and APP gained 27.9% and 36.2% more weight, respectively, than fish fed diets with 50 mg ascorbic acidkg diet from AA. These results indicated nearly equal ascorbic acid activity from AS and APP.     

Responses of Juvenile Golden Shiner Notemigonus crysoleucas Fed Semipurified or Practical Diets With or Without Supplemental Ascorbic Acid

A 12-wk feeding trial was conducted in a flow-through system to determine whether juvenile golden shiner Notemigonus crysoleucas have a dietary requirement for ascorbic acid. Triplicate groups of 30 fish each weighing 0.44 g initially were fed semi-purified (casein) diets supplemented with 0 or 250 mg ascorbic acid/kg, or practical (fish meal) diets supplemented with 0 or 250 mg ascorbic acid/kg. The form of ascorbic acid used was L-ascorbyl-2-polyphosphate. Survival was higher in fish fed the semi-purified diet with 250 mg ascorbic acid/kg than in those fed the unsupplemented semi-purified diet, while weight gain did not differ between treatments. Weight gain was higher in fish fed the practical (fish meal) diet supplemented with 250 mg ascorbic acid/kg than in those fed the unsupplemented practical diet, while survival did not differ between treatments. No other signs of ascorbic acid deficiency were observed, but fish fed the casein diets had skin and fin erosion indicative of a possible bacterial infection. Whole-body concentrations of ascorbic acid (total, reduced, and percent of reduced ascorbic acid) were higher in fish fed semi-purified or practical diets supplemented with 250 mg ascorbic acid/kg than in fish fed unsupplemented diets. Golden shiners appear to require a dietary source of ascorbic acid for growth or survival, depending on experimental conditions. The two main differences in the study were in diet composition (semi-purified versus practical diets) and apparent health status of fish fed the different diet types. Additional studies are needed to define requirements further.     

Growth performance,vitamin E status,and proximate and fatty acid composition of channel catfish, <Emphasis Type="Italic">Ictalurus punctatus</Emphasis>, fed diets containing various levels of fish oil and vitamin E

A study was conducted to determine the effect of increasing dietary levels of fish oil on vitamin E requirement and their effect on growth performance, liver vitamin E status, and tissue proximate and fatty acid compositions of channel catfish. Basal purified diets (42% protein and 3,800 kcal DE/kg) supplemented with 6, 10, and 14% menhaden fish oil were each supplemented with 50, 100, and 200 mg vitamin E/kg (3 × 3 factorial experiment). Each diet was fed to juvenile channel catfish in three random aquaria to apparent satiation twice daily for 12 weeks. Weight gain, feed intake, and feed efficiency ratio were not affected by dietary levels of fish oil, vitamin E, or their interaction. Survival rate at the end of week 12 was significantly lower for fish fed diets containing 14% fish oil, regardless of vitamin E content. Whole-body moisture significantly decreased and lipid increased when dietary lipid levels were increased to 10 or 14%. Dietary vitamin E levels had no effect on body proximate composition. Lipid content of liver was not influenced by dietary levels of fish oil and vitamin E or their interaction. Hepatosomatic index significantly decreased with increasing lipid levels but was not affected by dietary levels of vitamin E. Liver vitamin E increased with increasing dietary vitamin E but decreased with increasing fish oil levels. Fatty acid composition of whole body and liver reflected that of dietary lipid but was not influenced by dietary levels of vitamin E. Whole-body saturates increased, whereas MUFA decreased with increasing dietary levels of fish oil. Liver saturates were not affected by fish oil levels, but MUFA and n-6 decreased and increased, respectively, with increasing fish oil levels. Total n-3 and n-3 HUFA in both tissues increased with increasing fish oil levels in diets, but liver stored much higher levels of these fatty acids.     

Effect of Dietary Vitamin C on Weight Gain,Tissue Ascorbate Concentration,Stress Response,and Disease Resistance of Channel Catfish Ictalurus punctatus1

Juvenile channel catfish Ictalurus punctatus (average initial weight, 6.5 g/fish) were fed twice daily to apparent satiation with practical-type diets containing 0, 50, 150, or 250 mg supplemental vitamin C/kg from L-ascorbyl-2-polyphosphate for 10 wk under laboratory conditions. At the end of the feeding period, one half of the fish were stressed for 2 h by confinement and both stressed and nonstressed fish were exposed to a virulent strain of Edwardsiella ictaluri. Weight gain and feed conversion efficiency were lower for fish fed the basal diet than those fed diets containing supplemental vitamin C. No differences were observed in weight gain and feed conversion among fish fed diets containing supplemental vitamin C. There were no differences in feed consumption and survival (prior to experimental infection) among treatments. No vitamin C deficiency signs except reduced weight gain were observed in fish fed the basal diet. Serum cortisol concentrations were higher in stressed fish than in non-stressed fish. Dietary vitamin C level had no effect on serum cortisol concentration. As dietary vitamin C increased, ascorbate concentration in serum and liver increased. Confinement stress had no effect on serum and liver ascorbate concentrations. Cumulative mortality of channel catfish 21 d subsequent to experimental infection with E. ictaluri was higher for stressed fish than for nonstressed fish. Regardless of stress or nonstress, overall mortality for fish fed the basal diet was lower than the fish fed diets containing supplemental vitamin C. There were no differences in post-infection antibody levels among treatments or between stressed and nonstressed fish. Results from this study indicate that channel catfish require no more than 50 mg/kg dietary vitamin C for normal growth, stress response, and disease resistance.     

Dietary rutin has limited synergistic effects on vitamin C nutrition of fingerling channel catfish (Ictalurus punctatus)

A study was conducted to determine the possible synergistic effects between dietary rutin (a bioflavonoid) and vitamin C, and to evaluate their antioxidant effects in fingerling channel catfish. Purified casein/gelatin diets containing two levels of rutin (0 and 1000 mg/kg diet) and three levels of L-ascorbic acid (0, 1500 and 3000 mg/kg diet) in a factorial arrangement were fed to fingerling channel catfish for 16 weeks. Fish fed the diets without supplemental vitamin C showed deformed spinal columns, external hemorrhages and fin erosion after 10 to 12 weeks. Also these fish had significantly (p < 0.05) depressed body weight gain, feed efficiency, hematocrit, hepatosomatic index (% liver weight), as well as reduced liver, fillet and plasma vitamin concentrations after 16 weeks. Liver, fillet and plasma vitamin C concentrations were correlated with dietary vitamin C levels. Forced oxidation of fillet samples significantly (p < 0.05) increased 2-thiobarbituric acid (TBA) values of fillets from fish fed diets without vitamin C and rutin. However, results from the present study indicated only limited synergistic effects of dietary rutin on vitamin C nutrition of channel catfish.     

Ascorbic acid status as affected by dietary treatment in the Siberian sturgeon (Acipenser baeri Brandt): tissue concentration,mobilisation and L-gulonolactone oxidase activity

A study was conducted to evaluate tissue storage and mobilisation of L-ascorbic acid (AA) in the Siberian sturgeon (Acipenser baeri) fed three different experimental diets. The three treatments consisted of a diet devoid of vitamin C (diet A0) and two diets supplemented with equivalent of 300 mg AA kg^–1 in the form of either silicone-coated ascorbic acid (diet SC) or of ascorbyl-2-polyphosphate (diet AP). During the first phase (4 months) of the trial, six batches of 130 Siberian sturgeon (initial body weight: 25.5±0.5 g) each were fed one of the three diets in duplicate. During the second phase (3 months), fish from groups SC and AP were switched to diet A0 and those fed diet A0 during the first phase were switched to diet SC. Irrespective of the dietary treatment, growth rates were not significantly different from each other. At the end of phase I, in all tissues studied, total ascorbic acid (TAA) concentrations were higher in Siberian sturgeon fed diet AP than in the other two groups. During phase II, tissue ascorbate depletion was also higher in the AP group than in the other two groups. Transfer of the AA-free diet fed group onto a diet supplemented with 300 mg AA kg^–1 (diet SC) led to a slight increase in the TAA concentrations in all tissues. Blood plasma tyrosine concentrations were not significantly different between the three groups. Whole-body collagen levels were affected by dietary AA levels or forms at the end of phase I; the differences were not significant at the end of phase II. Muscle collagen levels were slightly affected. L-Gulonolactone oxidase activity was found in the kidney of Siberian sturgeon, but not in the liver. The ascorbyl-2-polyphosphate appears to be either better utilised by Siberian sturgeon, like in many other teleosts, or more stable than the silicone-coated AA during food processing and storage. Presence of L-gulonolactone oxidase activity in Siberian sturgeon kidney combined with the absence of gross scorbutic signs in AA-free diet fed groups expressing very good growth rates suggested no need of dietary AA byA. baeri.     

Dietary ascorbic acid requirement for growth of striped catfish,Pangasianodon hypophthalmus (Sauvage, 1878) juveniles

A sixty‐day feeding trial was conducted to determine the ascorbic acid (AA) requirement for growth of striped catfish, Pangasianodon hypophthalmus juveniles. Seven iso‐nitrogenous and iso‐energetic (370 g protein per kg and 19.6 MJ/kg) purified diets were prepared with different levels of ascorbic acid such as control (0), T₁ (17.5), T₂ (35), T₃ (70), T₄ (175), T₅ (350) and T₆ (700) mg ascorbic acid (L‐ascorbyl‐2‐polyphosphate) equivalent per kg diet. Fish with a mean body weight of 3.2–3.4 g were stocked (fifteen fish per tank) in triplicates following a completely randomized design. Each group was fed to satiation twice a day for 60 days. Significant differences were observed in growth, survival, body composition and metabolic enzymes activities with different dietary ascorbic acid levels. Maximum weight gain, specific growth rate (SGR) and protein efficiency ratio (PER) were found in fishes fed with 35 mg AA per kg diet, supported by best feed conversion. Fish fed a diet containing vitamin C had the highest activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) compared to those fed with vitamin C‐depleted diets. In this study, based on using broken‐line regression analysis, the dietary vitamin C requirement for growth of P. hypophthalmus juveniles was estimated to be in the range of 46–76 mg AA per kg, depending on the criterion used, growth and liver storage. Our results will be helpful for the formulation of cost‐effective ascorbic acid incorporated diets for striped catfish, P. hypophthalmus.     

'Broken-Skull Disease' in African Catfish Clarias gariepinus is Related to a Dietary Deficiency of Ascorbic Acid

Abstract.— Diets containing 0. 23, 46, 69, 92, and 185 mg ascorbic acid/kg of diet were fed to African catfish Clarias gariepinus juveniles (average initial weight, 19.9 g) for 20 wk in glass aquaria. Fish fed diets supplemented with 0 or 23 mg ascorbic acid/kg showed overt signs of broken-skull disease, such as hemorrhages along the spinal column and inflammation of dorsal skull bone followed by broken skull and death. They also had significantly lower vertebral collagen content and had significantly higher mortality than fish fed 46 mg or more ascorbic acid/kg of diet. Results from this study indicate that a dietary deficiency of ascorbic acid can cause broken-skull disease and high mortality in African catfish. A concentration of 46 mg ascorbic acid/kg of diet will prevent this anomaly and allow optimum synthesis of vertebral collagen.     

Optimum Dietary Level of L-ascorbic Acid for Japanese Eel, Anguilla japonica

A feeding experiment was conducted to determine the optimum dietary level of ascorbic acid (AsA) for Japanese eel juveniles using L-ascorbic acid Ca based on growth, AsA content in tissues, hematology, and bactericidal activity of serum with Escherichia coli . Test diets with six levels of AsA (3, 10, 27,126, 645, and 3,135-mg/kg diet) as Ca ascorbate were fed to juvenile Japanese eels (11.0 ± 0.2 g) once a day for 8 wk. High survival rates (> 80%) were observed among all dietary treatment groups. The specific growth rates of the fish fed diets containing 3 and 10-mg AsA/kg were significantly (P < 0.05) lower than those of other groups. Liver and brain AsA contents of the fish fed diets containing 3, 10, and 27-mg AsA/kg were significantly (P < 0.05) lower than those of the fish fed diets containing 645 and 3,135-mg AsA/kg. Hemoglobin content tended to be higher in the fish fed diets containing 645 and 3,135-mg AsA/kg than those of the fish fed other diets. Hematocrit value and total serum protein content of the fish fed diets containing 645 and 3135 mg AsA/kg were significantly (P < 0.05) higher than those of the other groups. The fish fed diets containing more than 27-mg AsAlkg showed a higher bactericidal activity of serum than the fish fed the diets containing 3-mg and 10-mg AsA/kg. The optimum dietary level of AsA for the Japanese eel juveniles growth was estimated to be more than 27-mg AsA/kg. Furthermore, the inclusion of 645-mg AsA/kg or more also increased the hematocrit, hemoglobin, total serum protein value, and liver and brain vitamin C concentrations.     

Effect of Dietary Vitamin C on Tissue Vitamin C Concentration in Channel Catfish,Ictalurus punctatus,and Clearance Rate at Two Temperatures-A Preliminary Investigation

Four trials were conducted with channel catfish, Ictalurus punctatus, under controlled laboratory conditions or in earthen ponds, to evaluate effects of dietary vitamin C concentration and feeding period on liver and anterior kidney vitamin C concentration. Clearance rate of vitamin C in liver and anterior kidney was also evaluated in unfed fish or fish fed a vitamin C-free diet. Results indicated that tissue vitamin C concentration is generally proportional to deitary vitamin C concentration, and that it may reach a maximum concentration within 2 weeks in fish fed diets containing vitamin C. Tissue vitamin C may be reduced to a minimum concentration within 2 weeks when fish were not fed or fed with a vitamin C-free diet at a high temprerature (31°). As temperature was reduced from 31 to 10°C there was a 44% and 13.6% drop in liver and anterior kidney vitamin C concentrations, respectively. At 10°C tissue vitamin C remained relatively constant (100 to 120 mg/g for liver, and 200 to 250 mg/g for anterior kidney) for at least 12 weeks if tissue vitamin C was saturated prior to reducing water temperature. Liver vitamin C appeared to be affected more dramatically by dietary vitamin C concentration and cleared more rapidly than anterior kidney during times of vitamin C deficiency.     

Biological efficacy of ROVIMIX STAY-C as a source of vitamin C for Salmonids

Abstract. L-ascorbate-2-polyphosphate (brand name: ROVIMIX STAY-C) is a vitamin C derivative which is highly stable during feed processing and storage. Trials were run to determine the biological efficacy of L-ascorbate-2-polyphosphate (AAPP) in comparison to a coated ascorbic acid form (AASC).
Bioavailability was studied by force-feeding rainbow trout, Oncorhynchus mykiss (Wal- baum), a single dose of both ascorbate forms and evaluating the kinetics of plasma ascorbic acid (AA).
Growth performance and tissue concentrations of ascorbic acid in liver, anterior kidney and plasma were compared in rainbow trout (initial body weight: 9g) fed a practical diet containing AAPP at 60, 200 or 1000 mg AA equivalent/kg feed. Two other groups were fed either no vitamin C or AASC at 200 mg/kg. Liver AA contents were monitored after 0, 10, 20, 30, 60 and 157 days of experimental feeding, while head kidney and plasma AA contents were measured at day 157.
Atlantic salmon of the start-feeding stage received a practical diet containing AAPP at 0,60 or 200 mg A A equivalent/kg. AAPP was compared to AASC at the equimolar dose of 200mg/kg. Liver AA contents were measured after 14, 47, 124 and 205 days of feeding. Head kidney and plasma AA levels were also analysed at the end of the trial.
Results showed that AAPP and AASC were equally bioavailable, thus suggesting that ascorbate-2-polyphosphate is absorbed in the blood as free ascorbic acid. In both Atlantic salmon, Salmo salar L., and rainbow trout, liver AA levels reflected well the dietary dose of ascorbate. At the 200mg/kg dose, ROVIMIX STAY-C supported higher vitamin C hepatic levels than did coated ascorbic acid.     

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.     

Feed efficiency, nutrient retention and body composition of Nile tilapia, Oreochromis niloticus L., fed diets containing L-ascorbic acid, L-ascorbyl-2-sulphate or L-ascorbyl-2-polyphosphate

Seven purified diets were formulated and fed to seven groups of Nile tilapia, Oreochromis niloticus L., fingerlings for 12 weeks. Six of the formulated diets contained 5 or 50 mg kg^?1 of ascorbic acid equivalent supplied by either L-ascorbic acid (AA), L-ascorbyl-2-sulphate (AS) or L-ascorbyl-2-polyphosphate (APP). The seventh basal diet was ascorbate-free and served as the control. The results of diet analysis for ascorbic acid showed that it was not detected or negligible in the control diet and in the diets containing AA at the end of the experiment, whereas there was no loss of ascorbic acid from diets prepared with AS or APP. The results demonstrated that the feed efficiency and growth parameters in fish fed APP-5, AS-5, AA-5 or AA-50 diets were statistically similar to the same parameters in fish fed the control diet. The study indicated that diets supplemented with 5 or 50 mg kg^?1 ascorbic acid in the form of APP or AS were more effectively utilized as sources of vitamin C than equimolar AA in promoting growth, improving food efficiency, increasing nutrient retention and preventing scurvy in Nile tilapia. Fish fed the ascorbate-free diet and the diet containing 5 mg AA kg^?1 exhibited external signs of scurvy during the last growth period of the experiment. Diets containing 5 mg kg^?1 of ascorbic acid from AS or APP provided some growth with no overt signs of scurvy, indicating that this concentration of AS and APP might be near the minimum requirement for the species. The APP-50 diet was the most efficient, and significantly (P < 0.05), had the lowest value of the amount of dietary protein necessary for 100 g weight gain (dietary protein index, DPI), the highest values of feed conversion efficiency (FCE) and the highest values of nutrient retention, i.e. protein (PRV), fat (FRV), ash (ARV) and gross energy (ERV) compared to the other diets. Fish that received the APP-50 diet had a significantly (P < 0.05) higher weight and protein gains in tissues than the other fish groups. The increase in the feed efficiency and growth parameter values in fish receiving the APP-50 diet compared with the values for the same parameters in the AA-50 diet were calculated as percentages, and the results were: weight gain, 36.2%; protein gain, 40.9%; FCE, 53.3%; PRV, 58.1%; FRV, 34.9%; ARV, 57.4%; and ERV, 51.9%. The diet containing APP-50 was followed in order by the AS-50 diet. The AS-50 diet had statistically comparable (P > 0.05) values of weight gain, protein gain and FRV to the APP-50 diet. The increased feed efficiency and growth parameters values of fish receiving the AS-50 diet compared with the AA-50 diet were calculated as percentages, and the results were: weight gain, 2 7.9%; protein gain, 27.9%; FCE, 18.2%; PRV, 17.9%; FRV, 19.2%; ARV, 8.9%; and ERV, 18.2%. There were no significant (P > 0.05) differences between the groups in the percentages of moisture, protein and ash in whole fish at the end of the study, whereas lipid percentages were significantly (P < 0.05) lower in all the tested groups in comparison with the control fish. Increasing the level of ascorbic acid equivalent from 5 to 50 mg kg^?1 diet from APP, AS or AA reduced the percentage of fat in Nile tilapia bodies. These results indicate that all the tested vitamin C sources were effective in inducing lipolysis in Nile tilapia tissues.     

Depletion of ascorbic acid derivatives in fish feed by the production process

ABSTRACT:   The depletion of ascorbic acid derivatives in fish feed during the feed processing (extrusion cooking and drying) was studied at five extrusion cooking temperatures and at 85°C for 2 h dryer processing temperature. Three ascorbic acid derivatives were used: L-ascorbyl-2-mono-phosphate Mg (APM), L-ascorbic acid sodium (AAS) and L-ascorbic acid palmitic acid ester (AAP). Samples were collected after drying and ascorbic acid derivatives losses evaluated. APM was found to be quiet stable with an average retention of 88%, but AAS and AAP were unstable and the depletion was very high.     

Effects of dietary vitamin C on growth and parr-smolt transformation in Atlantic salmon, Salmo salar L.

Atlantic salmon (Salmo salar) parr were fed fish meal based pelleted diets supplemented with graded levels of ascorbate-2-monophosphate (AP), equivalent to 0, 20, 60 and 1000 mg ascorbic acid (AA) kg”¹ throughout smoltification on a continuous light regime from February to June. No differences were observed in growth rate and body length distribution between the dietary regimes. The condition factor and the hepatosomatic index were somewhat elevated in fish fed no vitamin C throughout the smoltification, which can reflect changes in lipid metabolism in fish with suboptimal vitamin C nutrition. Sea water challenge tests (exposure to sea water with salinity of 34 gL^?1 and ambient temperature for 24 h) performed monthly did not reveal differences attributed to the vitamin C status, as measured by mortality, serum chloride and cortisol concentrations, haematological parameters and liver and head kidney ascorbate concentrations after 24 h. Elevated serum cortisol concentrations most probably reflected stress in the challenge tests, and some lower concentrations in fish fed high vitamin C levels may indicate a certain stress-ameliorating effect. The present results do not, however, support the anticipation of increased requirement of dietary vitamin C above the minimum requirement during smoltification in Atlantic salmon.     

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

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

Re-evaluation of vitamin E supplementation of practical diets for channel catfish, Ictalurus punctatus, production

A 10-month feeding trial was performed with channel catfish, Ictalurus punctatus , to re-evaluate the minimum level of dietary vitamin E supplementation required under conditions of commercial production. Four levels (0, 15, 30 and 60 mg kg⁻¹ diet) of supplemental vitamin E were added as DL -α-tocopherol acetate to a typical commercial catfish diet. Sixteen 0.04-ha ponds were stocked in July, at a rate of 25 000 fish ha⁻¹, with two size classes (averaging 18 and 265 g fish⁻¹) of fingerling channel catfish, and each diet was fed to fish in four replicate ponds once daily to satiation. After 10 months of feeding, a total harvest was performed to obtain final production data, and samples were obtained from fish in all ponds. Liver and plasma samples were obtained for α-tocopherol determination, and liver, heart and muscle samples were processed for histological evaluation.
No discernible differences occurred among fish fed the different diets with respect to weight gain or survival. Mean production rate was 9734 kg ha⁻¹, with a final average fish weight of 0.53 kg. A significant ( P < 0.05) effect of diet was noted in plasma and liver α-tocopherol levels, which increased with dietary supplementation. An effect of size also was apparent, with plasma and liver α-tocopherol levels being higher in larger fish compared with smaller fish within a dietary treatment. Histological evaluation revealed no differences among fish fed the different dietary treatments. Based on the lack of overt histological signs of deficiency, it appears that the current level of vitamin E supplementation of commercial catfish diets may be reduced considerably with no detriment to channel catfish health or production.     

Effects of different dietary levels of L-ascorbyl-2-polyphosphate on growth and tissue vitamin C concentrations in juvenile olive flounder, Paralichthys olivaceus (Temminck et Schlegel)

This experiment was conducted to study the effects of different dietary levels of vitamin C, L‐ascorbyl‐2‐polyphosphate (ASPP), on growth and tissue vitamin C concentrations in juvenile olive flounder, Paralichthys olivaceus (Temminck et Schlegel). Fish were fed one of six semi‐purified diets containing an equivalent of 0, 25, 50, 75, 150, or 1500 mg ascorbic acid (AA) kg^?1 diet (C₀, C₂₅, C₅₀, C₇₅, C₁₅₀ or C₁₅₀₀) in the form of ASPP for 12 weeks. Weight gain (WG) and protein efficiency ratio (PER) of fish fed the C₀ diet were significantly lower than those of fish fed the other diets (P < 0.05), and WG and PER of fish fed the C₂₅, C₅₀ and C₇₅ diets were significantly lower than those of fish fed the C₁₅₀₀ diet (P < 0.05). Fish fed the C₀ diet exhibited vitamin C deficiency symptoms such as anorexia, scoliosis, cataract, exophthalmia and fin hemorrhage at the end of the 12‐week test. After 12 weeks of the feeding trial, AA concentrations from gill, kidney, and liver of fish fed the C₀, C₂₅, C₅₀ and C₇₅ diets were significantly lower than those of fish fed the C₁₅₀ and C₁₅₀₀ diets (P < 0.05). Based on broken line analyses for WG and PER, the optimum dietary levels of vitamin C were 91 and 93 mg AA kg^?1 diet respectively. These findings suggest that the dietary vitamin C requirement could be 93 mg AA kg^?1 diet to support reasonable growth, and greater than 150 mg AA kg^?1 diet may be required for AA saturation of major tissues for juvenile olive flounder under experimental conditions.     

Effects of the different levels of dietary vitamin C on growth and tissue ascorbic acid changes in parrot fish (Oplegnathus fasciatus)

An 11-week feeding trial was conducted to study the effects of the different levels of dietary vitamin C on growth, tissue ascorbic acid concentrations and histopathological changes in parrot fish. Casein and gelatin-based diets were formulated to contain 0, 60, 120, 240, 480 and 2000 mg l-ascorbic acid (AA) per kg diets on AA equivalent basis in the form of l-ascorbyl-2-monophosphate (AMP), 60 and 240 mg AA per kg diet as l-ascorbic acid. However, the analyzed AA levels were 0, 50, 100, 205, 426 and 1869 mg AA per kg diet in AMP supplemented diets; 36 and 149 mg AA per kg diet in l-ascorbic acid supplemented diets. Thus, the diets were designated as AA-free, AMP₅₀, AMP₁₀₀, AMP₂₀₅, AMP₄₂₆, AMP₁₈₆₉, AA₃₆ and AA₁₄₉. Fish averaging 3.9±0.06 g (mean±S.D.) randomly were fed the experimental diets in triplicate groups for 11 weeks. Weight gain (WG) of fish fed AMP₅₀ and AA₃₆ diets were significantly lower than those of the other groups, and fish fed AMP₁₈₆₉ diet showed a higher WG than did fish fed AMP₅₀, AMP₁₀₀, AMP₂₀₅, AA₃₆ and AA₁₄₉ diets (P<0.05). However, there was no significant difference in WG between fish fed diets AMP₄₂₆ and AMP₁₈₆₉, and among fish fed AMP₁₀₀, AMP₂₀₅, AMP₄₂₆ and AA₁₄₉ diets. Fish fed the AA-free diet began to show deficiency signs, such as retarded growth, darkening, anorexia and high mortality, after 3 weeks of feeding trial. After 6 weeks of the feeding trial, liver from fish fed the AA-free diet showed severe atrophy. By the end of the seventh week, all fish fed the AA-free diet were dead. Liver AA concentration from fish fed AMP₅₀ diet was significantly lower than that from fish fed AMP₂₀₅, AMP₄₂₆, AMP₁₈₆₉ and AA₁₄₉ diets, and fish fed AMP₅₀, AMP₁₀₀, AA₃₆ diets showed a significant lower AA concentration in liver than did fish fed AMP₂₀₅, AMP₄₂₆ and AMP₁₈₆₉ diets.Broken line analysis of weight gain indicated that the dietary vitamin C requirement of parrot fish is 118±12 mg AA per kg diet in the form of l-ascorbyl-2-monophosphate for maximum growth.     

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.