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 300mg -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 6weeks. 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 300mg/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 300mg/kg vitamin E treatment. A lower malondialdehyde (MDA) content and higher phenoloxidase (PO) activity were observed in the crab fed 300mg/kg vitamin E. The results of this study indicate that the Chinese mitten crab fed the diet with 6% fish oil and 300mg/kg vitamin E showed better growth, antioxidant capacity and resistance to Aeromonas hydrophila.

A 10-week feeding trial was conducted to evaluate the effects of dietary lipid sources on the growth and immune responses of Chinese mitten crab Eriocheir sinensis. Six isonitrogenous and isoenergetic diets were formulated with fish oil (FO), linseed oil (LO), soybean oil (SO), rapeseed oil (RO), coconut oil (CO) and beef tallow (BT) as the sources of lipid with five replicates each. Thirty crabs (2.35 ± 0.14 g) were stocked into each tank and fed twice daily. Weight gain and specific growth rate of crab fed the FO diet were significantly lower than those fed other diets (P < 0.05), except for crabs fed LO diet (P < 0.05). Crab fed the SO diet weighed more than those fed FO diets (P < 0.05). Serum superoxide dismutase and malondialdehyde of crab fed the FO diet were significantly higher than in other groups (P < 0.05). Crab fed the FO diet had the highest activities of serum phenoloxidase, acid phosphatase, alkaline phosphatase and lysozyme (P < 0.05). The fatty acid composition in the liver of crab reflected the change in test diets. Our results indicate that the use of dietary vegetable or animal oils can achieve similar growth performance to the use of dietary FO in Chinese mitten crab, but non-FOs may impair crab immunity. Soybean oil is recommended as a suitable replacer for FO in Chinese mitten crab diet.

Experimental diets were formulated containing six levels of linolenic acid (0%, 0.5%, 1.0%, 1.5%, 2.0% and 2.5%) and each diet was fed to darkbarbel catfish Pelteobagrus vachelli in triplicate for 84 days. Weight gain, specific growth rate and feed efficiency increased with the increasing levels of dietary linolenic acid, but were not significantly different among diets containing 1.0%, 1.5%, 2.0% and 2.5% linolenic acid. Red blood cell count and haemoglobin were significantly higher in fish fed the 1.0% linolenic acid than other diets. Lysozyme activity and immunoglobulin M content in fish fed 1.0% of linolenic acid were significantly higher compared with the other diets. Antibody titre in fish fed 1.0–2.5% linolenic acids was significantly higher than in fish fed 0 or 0.5% linolenic acid 14 days after Aeromonas hydrophila challenge. This study indicates that linolenic acid is essential to darkbarbel catfish. Two-straight broken-line analysis with SGR showed that a dietary level of 1.29% linolenic acid is the minimum required for adequate growth of darkbarbel catfish. Considering other measured indicators of fish performance, a level of 1.0–1.5% linolenic acid in the diet is recommended for the darkbarbel catfish.

The Chinese mitten crab (Eriocheir sinensis) is an important economic aquatic animal farmed in China, and is increasingly being exported as a worldwide food. E. sinensis is umami, sweet, and rich in nutrients. There is a lack of wild Chinese mitten crab that cannot meet the needs of increasing consumption. Therefore, determining the nutrient requirement for this crab is important for developing its aquaculture. Selenium is a component of the enzyme glu-tathione (GPx), which can protect cell membranes against oxidative damage. It also converts hydrogen peroxide and fatty acid hydroperoxides into water and fatty acid alcohol using reduced glutathione. However, the requirement for selenium of the Chinese mitten crab is unknown. Organic Se has higher bioavailability than the inorganic Se. Therefore, a 6-week feeding trial was conducted to investigate the effects of dietary Se supplementation on the growth perform-ance, body composition and antioxidant status of juvenile Chinese mitten crabs. Six diets containing 0, 0.2, 0.4, 0.6, 0.8 and 1.0 mg/kg selenium were fed to quadruplicate juvenile Chinese mitten crabs (0.27±0.01) g, respectively, with 30 crabs in every aquarium. The results showed that juvenile E. sinensis fed the diet with 0.4 mg/kg(diet) Se supplementa-tion obtained the highest weight gain, survival rate and whole body crude protein content among the various groups (P<0.05). Hepatopancreas and muscle selenium contents were positively related to the dietary Se supplementation. Both serum and hepatopancreas glutathione peroxidase activities increased with increasing dietary Se level, and peaked at 0.4 mg/kg(P<0.05). When dietary Se increased to 0.8 mg/kg, serum glutathione peroxidase activity decreased significantly (P<0.05). The highest serum glutathione reductase activity was observed in the crab fed diet of Se level 0.4 mg/kg (P<0.05). The malonaldehyde content initially decreased and then increased with increasing dietary Se supplementation. Crabs fed the 0.4 mg/kg diet had the lowest malonaldehyde content, and differed from that of the control and 1.0 mg/kg groups(P<0.05). Crabs fed a diet containing less than 0.6 mg/kg selenium had lower glutathione levels compared with crabs fed 0.8 mg/kg and 1.0 mg/kg (P<0.05). The results indicated that dietary selenium supplementation of 0.4-0.6 mg/kg (total selenium of 0.43-0.66 mg/kg) can promote growth, use of dietary protein and anti-oxidative ability of ju-venile Chinese mitten crabs. Quadrate broken line analysis with serum GPx showed that a level of 0.51 mg/kg selenium supplementation (total selenium is 0.59 mg/kg) could meet the optimal anti-oxidative status of juvenile Chinese mitten crabs.

Traditionally, fish oil is the main lipid source in the feed for most species in aquaculture owing to its effective supply of energy and high content of essential fatty acid. The fatty acid especially n-3 HUFA from the fish oil had also been proved to have positive effect on maintaining the immune system. However, the decline of fish oil production from wild fisheries has resulted in a supply shortage and price escalation of fish oil. Therefore, it has been a major challenge to find viable sources of oil to substitute fish oil. Among available vegetable oils, soybean oil has been widely chosen due to its availability, price and abundant content of fatty acid. In this study, we evaluated the effects of diets with different fish oil and soybean oil ratios on grouth, non-specific immune response and disease resistance in Chinese mitten crab (Eriocheir sinensis). Five isonitrogenous and isoenergetic diets were for-mulated in which 0%(control:F1), 25%, 50%, 75%, or 100%(F2-F5) of the fish oil was replaced with soybean oil. Juvenile crabs (mean weight 0.27±0.03 g) were assigned to one of five treatment groups (four replicates per group) and fed one of the diets for 42 d. There was no significant difference in the survival rate among the treatments (P>0.05). The weight gain was significantly higher in the F4 group than in the F1 group (P<0.05). Similarly, the crabs in the F4 group had significantly higher serum ACP (acid phosphatase), AKP (alkaline phosphatase), and serum SOD (superoxide dismutase) activities than the other treatment groups (P<0.05). F4 and F3 group were significantly higher than the other groups (P<0.05). Serum MDA (malondialdehyde) content was significantly higher in the F1 group than in the other groups, but there was no difference between the other groups (P>0.05). Serum PO (phenoloxidase) activity was higher in F4 and lower in F5 than the other groups (P<0.05). There was no difference in serum lysozyme activity among the groups (P>0.05). After the feeding experiment, the crabs were infected with Aeromonas hydrophila for 10 d. The first death was recorded in F5, and the crabs in F5 had significantly higher cumulative mortality than those in F1 and F4 (P<0.05), but there was no significant difference among the other groups (P>0.05). In conclusion, complete substitu-tion of fish oil with soybean oil did not affect growth performance, but did reduce the ability to resist disease. Our re-sults suggest that replacement of 75%fish oil with soybean oil in the diet of Chinese mitten crab can improve growth with little effect on disease resistance.

This study was conducted to evaluate the effects of dietary methionine supplementation in cottonseed mealbased diets on the growth performance,digestibility and antioxidant ability of juvenile Chinese mitten crab,Eriocheir sinensis.Five diets were formulated using a basic diet,in which cottonseed meal accounted for 40%,supplemented with 0.00%,0.14%,0.28%,0.42%,and 0.56% methionine,respectively.Another diet was full fish meal-based(fish meal accounted for 64.4%) and served as the control.Each diet was fed to juvenile E.sinensis [(0.39±0.02) g] of five replicates for 6 weeks.The results showed that weight gain,specific growth rate and feed conversion ratio in crabs fed 0.42%Met diet did not differ from those of the control group(P0.05).Crabs fed with 0.28%Met and 0.42% Metdiets exhibited higher food intake and protein deposition rate than those fed diets with 0.00%Met,0.14%Met,0.56%Met(P0.05).There were no significant differences in whole body moisture,lipid,and ash(P0.05) among all treatments.However,compared with the 0.00% Met diets group,crude protein contents in crab fed with methionine supplemented diets were significantly higher(P0.05).Dry matter,protein,lipid digestibility,and trypsinase activity of crabs fed with 0.42% Metdiets did not differ from those of the control(P0.05).No differences were found in malondiaedehyde content,serum superoxide dismutase and glutathione peroxidase activity in crabs fed with the control diet and those fed with 0.28% Met,0.42%Met and 0.56% Metdiets(P0.05).The results suggest that 0.42%Met added to the diet(cottonseed meal accounted for 40%) could significantly accelerate the growth performance,digestibility and antioxidant ability of juvenile E.sinensis.