Thiamine requirement of Chinese soft‐shelled turtle,Pelodiscus sinensis (Wiegmann)

The objective of the present study was to estimate the dietary thiamine (vitamin B₁) requirement of juvenile soft‐shelled turtles, Pelodiscus sinensis. Eight experimental diets containing 0, 1.90, 3.63, 5.65, 7.51, 9.62, 11.37 and 13.64 mg thiamine/kg diet were fed to 160 soft‐shelled turtles reared individually for 10 weeks. The turtles had an average weight of 5.33 ± 0.21 g. Among all the dietary groups, weight gain, feed utilization and tissue thiamine were the lowest in the turtles fed with a thiamine‐free diet. The variables increased when dietary thiamine increased and then levelled off beyond 3.63 mg/kg diet. In contrast, plasma pyruvate and lactate concentrations in turtles decreased when dietary thiamine increased and then levelled off beyond 3.63 and 5.65 mg/kg diet respectively. Estimation using a broken‐line regression model, the vitamin B₁ requirement of soft‐shelled turtles was 3.2 mg thiamine/kg diet based on weight gain and plasma lactate concentration. When tissue thiamine and plasma pyruvate concentrations were used as the indicators, the estimated requirement was 5.4–6.5 mg/kg diet.     

Effects of dietary β‐carotene levels on growth and liver vitamin A concentrations of the soft‐shelled turtle,Pelodiscus sinensis (Wiegmann)

A feeding trial was conducted to evaluate the effect of dietary β‐carotene level on the growth and liver vitamin A concentrations in soft‐shelled turtles, Pelodiscus sinensis, fed a vitamin A‐free diet. Soft‐shelled turtles were fed diets containing 0, 14.5, 26.5, 47.5, 87.3, 112.8 and 163.8 mg β‐carotene kg^?1 for 10 weeks. Although it was not statistically significant due to high deviation within each group, mean weight gain of soft‐shelled turtles fed the diet without β‐carotene supplementation was the lowest among all test groups. Vitamin A concentrations in liver of turtles significantly (P<0.05) increased when dietary β‐carotene level reached 47.5 mg kg^?1 indicating that soft‐shelled turtles were capable of converting β‐carotene to vitamin A. Analysed by regression modelling, dietary β‐carotene levels for optimal growth and maximal liver vitamin A contents of juvenile soft‐shelled turtles fed the vitamin A‐free diets were 49.1 and 88.7 mg kg^?1 respectively.     

Effects of dietary zinc levels on growth,serum zinc,haematological parameters and tissue trace elements of soft‐shelled turtles,Pelodiscus sinensis

A 10‐week feeding trial was conducted to evaluate the effects of dietary zinc (Zn) contents on the growth, tissue trace element contents and serum Zn levels in soft‐shelled turtles, Pelodiscus sinensis. Juvenile soft‐shelled turtles approximately 4.8 g in body weight were fed casein‐based diets containing seven levels of Zn (14, 23, 32, 43, 58, 87 and 100 mg kg^?1) for 10 weeks. There were no significant differences (P > 0.05) in weight gain (WG), feed conversion ratio (FCR) or protein efficiency ratio (PER) among the dietary treatments. However, Zn concentrations in the liver, serum and carapace of turtles fed the basal diet containing 14 mg Zn kg^?1 were the lowest among all groups. Zn contents in the liver, serum and carapace increased when dietary Zn increased up to a dietary Zn level of approximately 43 mg kg^?1. Beyond this dietary level, tissue Zn contents were relatively constant. Carapace iron (Fe), selenium (Se) in hard tissues and haemoglobin concentrations decreased when dietary Zn increased. Dietary Zn requirements of juvenile soft‐shelled turtles derived from regression modelling using the liver, serum, carapace and bone Zn contents as indicators were 42, 39, 35 and 46 mg Zn kg^?1, respectively.     

Effects of dietary magnesium on the growth,carapace strength and tissue magnesium concentrations of soft‐shelled turtle,Pelodiscus sinensis (Wiegmann)

A feeding trial was conducted to evaluate the effects of dietary magnesium on the growth, carapace strength, tissue and serum Mg concentration of soft‐shelled turtles, Pelodiscus sinensis (Wiegmann). Juvenile soft‐shelled turtles of approximate 5.4 g body weight were fed diets with seven levels of Mg (48, 206, 369, 670, 955, 1195 and 1500 mg Mg kg^?1) for eight weeks. No significant difference (P ≥ 0.05) was found in weight gain (WG), feed conversion ratio or protein efficiency ratio among treatments. However, the WG of turtles continued to increase with increasing dietary Mg levels up to 670 mg kg^?1, beyond which the WG levelled off. The plasma alkaline phosphatase activity and the muscle, bone Mg concentrations of the turtles increased with the increasing dietary Mg levels between 48 and 955 mg kg^?1, beyond which the tissue Mg concentrations remained relatively constant. Furthermore, the carapace strengths of turtles fed with the control diet of 48 mg Mg kg^?1 were significantly weaker (P < 0.05) than that of turtles fed with diets containing higher Mg levels. Based on a broken‐line modelling analysis, the required dietary Mg level for the optimal WG of juvenile soft‐shelled turtles was estimated to be approximately 650 mg kg^?1. By contrast, the required dietary Mg levels for turtles to reach the optimal muscle and bone Mg concentrations were 1050 and 1000 mg kg^?1 respectively. The required dietary Mg level for maximal alkaline phosphatase activity was approximately 980 mg kg^?1.     

Effects of dietary vitamin E level on growth and tissue lipid peroxidation of soft-shelled turtle, Pelodiscus sinensis (Wiegmann)

A feeding trial was conducted to determine the effect of dietary vitamin E supplementation on growth, liver lipid peroxidation and liver and muscle vitamin E level of soft‐shelled turtle, Pelodiscus sinensis. Eight experimental diets analysed to contain 0–457 IU vitamin E kg^?1 were fed to juvenile soft‐shelled turtle of 4.8 g initial body weight for 12 weeks. Weight gain (WG) of the turtles fed the diet containing no vitamin E was significantly lower than those fed diets containing 83–457 IU vitamin E kg^?1 (P<0.05). Feed conversion ratio and protein efficiency ratio showed similar trends to that of WG. No significant difference (P>0.05) was found in whole‐body composition among turtles fed the different diets. Dietary vitamin E requirement using WG as the response and estimated using the broken‐line regression model is approximately 88 IU kg^?1. Liver and muscle vitamin E content increased when dietary vitamin E level increased. Ascorbate‐induced lipid peroxidation in liver tissue of turtles fed diets containing 0 and 17 IU vitamin E kg^?1 was significantly (P<0.05) greater than those fed diets containing high vitamin E (≥35 IU kg^?1).     

Protein‐sparing effects and LPL gene expressions of dietary lipids in the juvenile soft‐shelled turtle,Pelodiscussinensis

The aim of this study was to evaluate the effects of dietary lipids on protein‐sparing and lipoprotein lipase (LPL) mRNA expression in culture using 360 juvenile soft‐shelled turtles (Pelodiscussinensis) (initial weight 4.26 ± 0.14 g). The turtles were allotted to six diets with three duplicates for 60 days. A control diet with 46% protein and 55% fishmeal (CD) and five isonitrogenous diets with 41.3% protein and 45% fishmeal (F, S, L1, L2 and L3) were used, containing the following three lipid types: fish oil, soybean oil and mixed oils (soybean oil: fish oil = 1:1). The results showed that the survival rate was not affected by dietary lipids (P > 0.05). The highest weight gain and lowest feed coefficient ratio were seen in the L3 diets (P < 0.05). Turtles fed with L2 and L3 diets had lower superoxide dismutase activities, higher alanine aminotransferase activities and higher cholesterol concentrations than those exposed to other diets (P < 0.05). Hepatic LPL activity and LPL mRNA expression were higher in the L3 diets than in the other diets (P < 0.05). Overall, there were obvious protein‐sparing effects of dietary lipids and LPL mRNA expression was stimulated by high dietary lipids in soft‐shelled turtles in this study.     

The effect of vitamin C on stress withstanding capability in the juvenile soft-shelled turtle (Pelodiscus sinensis)

The study was conducted to determine the effect of dietary supplementation of vitamin C on anti‐acid stress ability in juvenile soft‐shelled turtle. The soft‐shelled turtles were fed vitamin C supplemented diets at levels of 0, 250, 500, 2500, 5000 and 10 000 mg kg^?1 for 4 weeks. The results showed that the phagocytic rate of blood cell in the group fed vitamin C deficient diets, the serum bacteriolytic activity in the two groups fed vitamin C supplemented diet at 0 and 250 mg kg^?1 and the serum bactericidal activity in all groups after acid stress significantly decreased compared with those of before stress (P < 0.1). The phagocytic rate of blood cells in the two groups fed vitamin C supplemented diet at 2500 and 5000 mg kg^?1 were significantly higher than those of the four groups fed at 0, 250, 500 and 10 000 mg kg^?1 (P < 0.01). The serum bacteriolytic activity in the groups fed vitamin C supplemented diet at 500, 2500, 5000 and 10 000 mg kg^?1 were significantly higher than that of the group fed vitamin C deficient diets (P < 0.05), and the two groups fed vitamin C at 2500 and 5000 mg kg^?1 were significantly higher than those of the groups fed at 250 and 10 000 mg kg^?1 (P < 0.05). The serum bactericidal activities in the four groups fed vitamin C supplemented diet at 500, 2500, 5000 and 10 000 mg kg^?1 were significantly higher than those of the two groups fed at 0 and 250 mg kg^?1 diet (P < 0.01), and the two groups fed vitamin C at 2500 and 5000 mg kg^?1 were significantly higher than those of the two groups fed at 500 and 10 000 mg kg^?1 (P < 0.1). These results suggest that supplementation of vitamin C higher than 250 mg kg^?1 is necessary to reduce the adverse effects of acid stress.     

Effects of dietary vitamin B1 on growth performance,blood metabolites,body composition,intestinal enzyme activities and morphometric parameters of juvenile yellow catfish (Pelteobagrus fulvidraco)

The effects of vitamin B₁ on growth, blood metabolites, body composition, intestinal enzyme activities and morphometric parameters were evaluated by a 63‐day feeding trial in Pelteobagrus fulvidraco fed diets containing vitamin B₁ with 4.29, 6.02, 7.86, 11.94 and 19.05 mg/kg, respectively. Results showed that 7.86 mg/kg vitamin B₁ resulted in significantly higher weight gain (WG), specific growth rate (SGR) and protein efficiency ratio (PER) (p < .05). Serum triglyceride, cholesterol and whole‐body lipid were observed in 11.94 mg/kg vitamin B₁ group significantly higher than those in 4.29 mg/kg group, accompanied by the lower serum glucose content in the same group (p < .05). Significantly higher values of whole‐body protein, serum total protein, relative intestinal length, fold height, intestinal trypsin, amylase, alkaline phosphatase, Na+/K+‐ATPase, γ‐glutamyl transpeptidase, creatine kinase, muscular layer thickness and intestosomatic index were observed in 7.86 mg/kg vitamin B₁ group compared with those in 4.29 mg/kg group (p < .05). These results suggested that diets supplemented with vitamin B₁ improved growth performance, feed utilization, intestinal digestive and absorption capacity of juvenile yellow catfish. The optimal dietary vitamin B₁ requirements estimated using a two‐slope broken‐line model based on WG and PER of yellow catfish were 7.42 and 6.01 mg/kg, respectively.     

Effect of dietary calcium and phosphorus supplementation in fish meal-based diets on the growth of soft-shelled turtle Pelodiscus sinensis (Wiegmann)

A growth experiment was conducted to determine the effect of supplementing dietary calcium in fish meal‐based diets on the growth of cultured soft‐shelled turtle Pelodiscus sinensis. Juvenile soft‐shelled turtles of 4.1 g mean body weight were fed nine diets containing two levels of phosphorus (2.7% or 3.0%) and analysed calcium levels ranging from 4.7% to 6.6% for 10 weeks. The growth of the turtles was enhanced when inorganic calcium was added to the diets. The weight gain of the turtles fed the control diet containing calcium solely from fish meal was the lowest among the test groups, and was significantly lower than those fed the diet containing 5.7% calcium at the 3.0% phosphorus level (P<0.05). Feed conversion and protein efficiency ratios were not affected by different dietary treatments. Whole‐body moisture and crude protein contents of turtles were not affected by different dietary treatments. The body ash of turtles fed 3.0% phosphorus diets tended to be higher than turtles fed 2.7% phosphorus diets. The body calcium to phosphorus ratio of turtles fed 3.0% phosphorus diets was greater than that of turtles fed diets containing 2.7% phosphorus. Supplementation of Ca in a fish meal‐based practical diet is required for the optimum growth of soft‐shelled turtles.     

Estimation of dietary vitamin A requirement of juvenile soft‐shelled turtle,Pelodiscus sinensis

A feeding trial was conducted to evaluate the dietary vitamin A requirement of the soft‐shelled turtle Pelodiscus sinensis. Turtles with an approximate body weight of 6.8 g were fed diets containing 0–4.58 mg kg^?1 (15 251 IU) vitamin A (retinyl acetate) for 8 weeks. Turtles fed diets without vitamin A showed the lowest growth performance. The animals gradually gained weight when dietary vitamin A increased from 0 to 3.6 mg kg^?1. Liver vitamin A gradually increased with supplementation of dietary vitamin A of up to 2.7 mg kg^?1. Beyond this concentration, the vitamin A in the liver significantly increased. Data analysis using a polynomial regression or exponential model showed that the estimated dietary vitamin A requirement for juvenile soft‐shelled turtles based on weight gain, red blood cell count and liver vitamin A measurements was 3.48, 2.84 and 2.58 mg kg^?1, respectively.     

Effect of dietary lipid source and vitamin E on growth,non‐specific immune response and resistance to Aeromonas hydrophila challenge of Chinese mitten crab Eriocheir sinensis

Six purified diets were formulated to contain three lipid sources, fish oil (FO), linseed oil (LO) and soybean oil (SO), at 6% diet lipid crossing two levels of vitamin E (100 and 300 mg α‐tocopheryl acetate/kg diet) for each lipid source (FO100, FO300, LO100, LO300, SO100, SO300). The juvenile Chinese mitten crab, Eriocheir sinensis, respectively, fed on these diets with four replicates for 6 weeks. The crab weight gain (WG) and specific growth rate (SGR) were significantly affected by dietary lipid sources. No difference was found between the crabs fed two levels of vitamin E, but the WG and SGR were numerically higher in crab fed 300 mg/kg vitamin E than those fed the other level of vitamin E. The lipid source and vitamin E level could affect fatty acid composition in the hepatopancreas. The contents of saturated fatty acids (SAFA) and n‐3HUFA were significantly higher in the crab‐fed fish oil. The highest contents of n‐6PUFA and n‐3PUFA were found in the crab‐fed soybean oil and linseed oil respectively. The contents of SAFA, n‐3HUFA and n‐3PUFA were higher in the 300 mg/kg vitamin E treatment. A lower malondialdehyde (MDA) content and higher phenoloxidase (PO) activity were observed in the crab fed 300 mg/kg vitamin E. The results of this study indicate that the Chinese mitten crab fed the diet with 6% fish oil and 300 mg/kg vitamin E showed better growth, antioxidant capacity and resistance to Aeromonas hydrophila.     

Effects of inorganic and organic dietary copper supplementation on growth performance and tissue composition for juvenile red drum (Sciaenops ocellatus L.)

A feeding trial was conducted to evaluate the dietary copper requirement of red drum (Sciaenops ocellatus) and compare the bioavailability of copper sulphate (CuSO₄) and copper‐ethanolamine. A basal diet was formulated using semi‐purified ingredients and analysed to contain 3 mg Cu/kg. Both copper sources were supplemented to the basal diet at either 5, 10 or 20 mg Cu/kg of dry diet. No significant differences were observed in growth performance of fish fed the various diets. However, red drum fed all copper‐supplemented diets retained more copper in liver and whole‐body tissues compared to fish fed the basal diet. Within both inorganic and organic copper treatments, the highest tissue copper concentrations were observed in fish fed diets supplemented with 10 mg Cu/kg. No significant differences were detected in net copper retention regardless of the nature of the copper source; hence, the bioavailability of copper sulphate and copper‐ethanolamine complex was not different in the diets for juvenile red drum. Furthermore, the minimum copper requirement for growth performance of juvenile red drum appeared to be satisfied when fish were fed the basal diet containing 3 mg Cu/kg diet, and no detrimental effects were observed in red drum fed diets supplemented with 20 mg Cu/kg.     

Efficacy and tolerance of lutein as colourant in diet of juvenile soft‐shelled turtle Pelodiscus sinensis

The effects of dietary supplementation of lutein on the growth, haematological profile and pigmentation in target tissues of the soft‐shelled turtles were investigated. Five experimental diets were prepared with lutein levels at 1.16 (D1, control), 70.3 (D2), 132 (D3) and 239 (D4) mg kg^?1, and one more high inclusion level of 3410 mg kg^?1 (D5) was included for tolerance test. Each diet was fed to 24 juvenile turtles for 8w. Specific growth rate (SGR) in D2, D3 and D4 was significantly higher than that of group D1 and D5. Skin yellowness (b*) and chroma (C*) of both carapace and plastron skin were all significantly increased with higher dietary lutein levels. Dietary lutein supplementation turned the H° values of skins into yellowness. The accumulation of lutein in skin and muscle also augmented significantly with increasing lutein levels and fit a logarithmic correlation with dietary lutein levels. There were almost no differences in haematological parameters of all turtles. Lutein is an efficient and safe colourant in diet of soft‐shelled turtle. The optimal inclusion levels for the highest SGR and desired skin colour in carapace and plastron of soft‐shelled turtle were 162, 142 and 143 mg kg^?1, respectively.     

Quantitative dietary copper requirement of juvenile Siberian sturgeon,Acipenser baerii,and effects on muscle composition and some enzymatic activities

An 8‐week feeding trial was conducted to quantify dietary copper (Cu) requirement of juvenile Siberian sturgeon, Acipenser baerii. Five isonitrogenous diets were formulated to provide actual dietary copper values of 1.8, 5.7, 10.1, 15.9 and 28.3 mg Cu per kg diet. Experimental diets were fed to the Siberian sturgeon (27.57 ± 0.24 g) in triplicate to apparent satiation for 8 weeks. At the end of experiment, weight gain (WG), specific growth rate (SGR) and protein efficiency ratio (PER) were significantly increased with increasing dietary Cu level up to 10.1 mg/kg and then decreased with further increases in dietary Cu level (p < .05). The Cu concentration in the liver and cartilage was positively correlated with the respective concentrations in the diet (p < .05), while muscle and serum Cu concentrations remained significantly unchanged (p > .05). Superoxide dismutase and glutathione peroxidase had the highest activities in serum of fish fed with 15.9 and 28.3 mg Cu per kg diet, respectively. Analysis by the broken‐line regression of SGR, crude protein content and superoxide activity demonstrated that the optimum dietary Cu requirements in juvenile Siberian sturgeon were 9.51, 9.58 and 16.10 mg/kg diet, respectively.     

The dietary zinc requirement of a benthic fish Paramisgurnus dabryanus

This study was conducted to assess the dietary zinc (Zn) on growth and antioxidant capacity of adult Paramisgurnus dabryanus. Zinc methionine (ZnM) of grade levels (0, 20, 40, 80, 120 and 160 mg/kg diet respectively) was supplemented, providing actual dietary Zn concentrations of 24.38, 28.03, 31.68, 38.98, 46.28 and 53.58 mg/kg diet respectively. P. dabryanus with an initial body weight of 5.21 ± 0.15 g were fed these Zn supplemented diets for 8 weeks. Results showed that the weight gain (WG) and specific growth rate (SGR) increased with increasing dietary Zn levels from 24.38 to 31.68 mg/kg, and then decreased above these levels. The hepatopancreas index (HIS) was the highest at 31.68 mg/kg, followed by 38.98 mg/kg. The enzymatic antioxidants in plasma and hepatopancreas firstly increased, and reached the peak at 31.68 or 38.98 mg/kg, then kept stable with the increase of dietary Zn levels. On the contrary, the content of MDA firstly decreased, and then increased. According to WG and T‐AOC in plasma, the Zn requirement was determined to be 32.02 and 32.24 mg/kg, respectively, based on regression analysis. The relatively low dietary Zn requirement of P. dabryanus may involve in the evolutional adaption of metal absorption and utilization to their habitat.     

The effects of vitamin E on non-specific immune response of the juvenile soft-shelled turtle <Emphasis Type="Italic">Pelodiscus sinensis</Emphasis>

ABSTRACT:   This study was conducted to determine the effect of dietary vitamin E supplements on non-specific immune responses in juvenile soft-shelled turtles. Turtles were fed diets supplemented with vitamin E at 0 (control), 50, 250, 500, 1000 and 5000 mg/kg, respectively, for 4 weeks. Results showed that blood cell phagocytosis and serum bactericidal activity were significantly improved in turtles from two diets (250 and 500 mg/kg vitamin E supplementation), while had no significant improvement in turtles from the three remaining diets (50, 1000 and 5000 mg/kg vitamin E supplementation) when compared to turtles from the control group. Serum bacteriolytic activity in turtles from diets with 50, 250, 500 and 1000 mg/kg vitamin E supplementation were higher than activity levels quantified for the control group, but no significant difference was observed between the 5000 mg/kg vitamin E supplementation diet and the control diet. The results suggest that vitamin E has an upper and lower threshold for improving non-specific immune function in soft-shelled turtles, and the optimal supplementation may be between 250 and 500 mg/kg.     

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.     

Effects of phospholipid addition to diets with different inclusion levels of fish oil on growth and fatty acid body composition of juvenile swimming crab Portunus trituberculatus

Six experimental diets were designed with two phospholipid (PL; 0% and 1.5%) and three fish oil levels (0%, 1% and 3%) to evaluate the effects of dietary fish oil and PL levels on growth, survival and fatty acid composition of juvenile swimming crab, Portunus trituberculatus. Diets were iso‐energetic and iso‐nitrogenous and each diet was fed to triplicate groups (initially weight, 24.88 ± 0.04 g per crab) for 59 days. Weight gain (WG) and specific growth rate (SGR) increased with dietary PL addition to 0% fish oil‐supplemented diets (P < 0.05). On the other hand, WG and SGR decreased with dietary PL addition to 3% fish oil diets (P < 0.05). Crabs fed PL supplemented diets had higher haemolymph low‐density lipoprotein cholesterol concentrations and muscle crude lipid levels (P < 0.05) than crabs fed a none PL supplemented diet. The percentage of highly unsaturated fatty acids (HUFA; % total FA) in both polar and neutral lipids fractions of muscle tissue only increased in case of PL addition to 0% and 1% fish oil‐supplemented diets (P < 0.05). HUFA levels in the neutral lipids fraction of the hepatopancreas increased by dietary PL addition at each dietary fish oil level (P < 0.05). In this study, both dietary fish oil and PL addition contributed to a high n‐3/n‐6 ratio in muscle and hepatopancreas of P. trituberculatus. In conclusion, PL addition is only meaningful with fish oil‐deficient diets, in which case it enhanced lipid transport and HUFA absorption efficiency, hence improving the nutritional value of the diet.     

Effect of dietary iron (Fe) levels on growth performance,hepatic lipid metabolism and antioxidant responses in juvenile yellow catfish Pelteobagrus fulvidraco

This study was conducted to determine effects of dietary Fe levels on growth performance, hepatic lipid metabolism and antioxidant response for juvenile yellow catfish Pelteobagrus fulvidraco. Yellow catfish were fed six isonitrogenous and isolipidic diets containing Fe levels of 16.20, 34.80, 54.50, 76.44, 100.42 and 118.25 mg/kg for 8 weeks. Weight gain (WG) and specific growth rate (SGR) increased with dietary Fe levels from 16.20 to 54.50 mg/kg diet and then plateaued over the level. Feed conversion rate (FCR) was highest and protein efficiency rate (PER) was lowest for fish fed the lowest Fe levels of diet. Fe contents in whole body and liver increased with increasing dietary Fe levels. Hepatic lipid content was lowest, but mRNA levels of carnitine palmitoyltransferase (CPT‐1) and peroxisome proliferator‐activated receptor α (PPARα) were highest for fish fed 54.50 mg Fe/kg diet. Fish fed adequate dietary Fe levels reduced hepatic malondialdehyde (MDA) level and increased activities of antioxidant enzymes Superoxide dismutase (SOD), Catalase (CAT) and GS. Based on the broken‐line regression analysis of WG against dietary Fe levels, optimal dietary Fe requirement for yellow catfish was 55.73 mg Fe/kg diets. Fe‐induced changes in MDA levels and antioxidant enzymatic activities paralleled with the change in hepatic lipid content, suggesting the potential relationship between oxidative stress and hepatic lipid accumulation in yellow catfish.