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In order to understand the effects of dietary curcumin on the growth and digestive performance of Seriola dumerili, this study was conducted under laboratory conditions. The control group was added with 0% curcumin, and two treatment groups were added with 0.01% and 0.02% curcumin, respectively. Fish were fed with experimental diet for 8 weeks. The growth data, growth genes, intestinal digestive enzymes, tissue parameters, and blood lipid-related indicators were measured, and the correlation between digestive indicators, growth gene indicators, and growth characteristic indicators was analyzed. The results showed that the survival rate, visceral ratio, hepatosomatic ratio, and condition factor of Seriola dumerili increased first and then decreased with the increase of curcumin content in feed. The feed conversion ratio of the control group was significantly higher than that of the treatment group. With the increase of curcumin content in feed, lipase and trypsin increased first and then decreased with the increase of curcumin content. Compared with the control group, curcumin significantly increased the muscle thickness and the number of goblet cells of Seriola dumerili. High and low contents of curcumin can reduce the content of serum total cholesterol and triglyceride, and a low dose (0.01%) of curcumin has the strongest lipid-lowering effect. The relative gene expression of IGF1 and IGF2 reached the maximum in the 0.02% treatment group. The results showed that the addition of curcumin in feed could theoretically improve the survival rate, feed efficiency, and other growth characteristics of Seriola dumerili, improve intestinal digestion and structure, promote intestinal health, and reduce blood lipid levels. The best effect was achieved in the 0.01% treatment group. The results of this study provide a theoretical reference for the feasibility of adding curcumin to Seriola dumerili feed in production and realize the optimal proportion of feed additives for this species, which is beneficial to the sustainable development of aquaculture.

Transportation is of high risk and cannot be avoided during the productive practice of Lates calcarifer fry. To achieve an optimal transporting protocol, the changes of physico‐chemical indexes and immune genes expression of fry after transportation were evaluated. The fish were simulated transported at the density of 7 kg/m3 for different time (T1 = 4 h, T2 = 8 h, T3 = 12 h, T4 = 16 h, T5 = 20 h, T6 = 24 h) and at three densities (D1 = 14 kg/m3, D2 = 21 kg/m3, D3 = 28 kg/m3) for 24 h. With the intensive stress, a decrease in pH and an increase in NH4+‐N were observed. At transporting density experiment, the cortisol of every group except T3 had a significant difference with the control. ALT, AST and ACP activity were all close to a rise first and then decline trend. IL‐8, TNF and IFN‐γ1 were activated to promote inflammation at different degrees of transportation pressure, while the tendency of L10 and TGF‐β1 was similar. CRP also had no significant increase under different transporting durations stress. HSP70 undertook main repair work as expression level of it increased gradually. Complement did not reach its release standard at duration experiment expect for T3 group of C3. However, density experiment had no obviously positive effects on physico‐chemical indexes and the relative expression of immune genes. The results indicated that when the transporting time exceeded 8 h at the density of 7 kg/m3, significant immune response started happening to fish. The transporting density stress has stimulated the fries but the immune response was still under the inhibited state owing to the ammonia toxicity reduction by much lower pH.

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This study was conducted to determine whether curcumin has a positive effect in greater amberjack (Seriola dumerili), especially the ammonia nitrogen stress tolerance ability. The results showed that the stress recovery process of digestive enzymes amylase and trypsin, as well as absorptive enzymes Na+/K+-ATPase, γ-GT and CK, was accelerated. Lysozyme activity increased in the fish fortified with both curcumin diets. Aspartate aminotransferase activity restriction was activated at a low curcumin level. However, alanine aminotransferase activity restriction happened only at 0.02% dietary curcumin. Facilitation of lipid metabolism by curcumin was very clear, as triglyceride and total cholesterol content was basically maintained at the original level or even showed a slight decrease after recovery. HSP70 and HSP90 genes were not evidently stimulated to express in liver, kidney and spleen tissues. In addition, curcumin showed its inhibition capacity on IL1β and IFN-γ and a promoting effect on TGF-β1. The expression of NF-κB1 decreased in a higher degree in fish fed with 0.02% dietary curcumin, while 0.01% dietary curcumin accelerated the recovery pace of C3 and lgT after stress. This study showed that dietary curcumin supplementation can enhance ammonia nitrogen stress tolerance in greater amberjack, and its application prospect can be confirmed.

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This study was aimed to evaluate the effects of feeding frequency on growth performance, antioxidant status and immunity of juvenile red swamp crayfish Procambarus clarkia (average weight: 3.01±0.02 g). Crayfish were randomly assigned to one of five feeding frequencies (1,2,3,4 and 5 times/day, F1, F2, F3, F4 and F5) following the same ration size for 60 days. After the feeding trial, fish were challenged with white spot syndrome virus (WSSV) and cumulative mortality was recorded for the next 4 days. The results showed that the weight gain rate (WGR) of crayfish tended to increase initially and then decrease as feeding frequency increased. The WGR in F3 were significantly higher than those fed 1, 4 and 5 times/ day (P<0.05). The highest serum lysozyme (LZM), lowest catalase (CAT) and malondialdehyde (MDA) were observed in crayfish fed 3 times/day. However, there were no significant differences in cortisol, glucose (Glu), and superoxide dismutase (SOD) among all groups (P>0.05). The cumulative mortality in F3 was significantly lower than that of the other groups at d4 after challenge (P<0.05). In conclusion, both low and high feeding frequencies could cause stress of juvenile Procambarus clarkia and the optimal feeding frequency to enhance growth and immunity of this species at juvenile stage is 3 times/day.

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