This experiment was designed to investigate the effects of curcumin levels on growth, flesh quality, and oxidative resistance in juvenile genetically improved farmed tilapia (GIFT, Oreochromis niloticus). Fish (initial mean weight: 4.50.3g) were randomly fed five diets with curcumin supplementation levels of 0 (control), 150, 300, 600, and 1,200mg/kg. After 60 days of feeding, the hepatosomatic index was significantly reduced in the curcumin supplemented groups. The 300mg/kg group had the highest crude protein content of the whole fish. Compared to the control group, the crude fat content of whole fish in the 150 and 300mg/kg groups was significantly reduced by 18.8319.74, respectively. The highest values for muscular hardness, chewiness, myofibrillar density, and proportion of small-sized myofibers (40μm) were observed in the 300mg/kg group. The levels of total nonessential amino acids and bitter amino acids in muscle were significantly lower in the 150 and 300mg/kg groups than in the other groups. The 300mg/kg group had higher levels of free sweet amino acids in the muscle than the other groups. Muscles from the 150, 300, and 600mg/kg groups had significantly higher levels of umami amino acids than in the other groups. The levels of total free nonessential amino acids and total amino acids in serum were significantly higher in the 300mg/kg group than in the control group. Serum aspartate transaminase activity was significantly lower in the curcumin supplementation groups than in the control group, and the serum alanine aminotransferase activity was significantly lower in the 150mg/kg group than in the other groups. Serum superoxide dismutase activity was significantly higher in the curcumin supplementation groups than in the control group. Serum catalase activity was significantly higher in the 150mg/kg group than in the other groups. The serum malondialdehyde level was lowest in the 150mg/kg group. These results suggest that dietary curcumin supplementation in the diet at 150300mg/kg can effectively improve the nutritional value, muscle flavor, and antioxidant capacity of tilapia.

Choline, an essential nutrient for aquatic animals, plays an important role in fish growth performance and health, but its effect on bighead carp is not yet known. To investigate the effects of choline chloride on growth performance, antioxidant properties, and intestinal function of juvenile bighead carp ( Aristichthys nobilis ), fish with an average weight of 1.77 ± 0.20 g were fed with different dietary choline chloride supplementation concentrations: 0 g/kg (control), 2, 4, 6, 8, and 10 g/kg for 66 days. The results indicated that dietary choline chloride supplementation at 6 g/kg improved the weight gain rate (WGR) and specific growth rate (SGR) ( p < 0.05). Dietary choline chloride supplementation (4–10 g/kg) decreased serum in serum triglycerides (TGs), total cholesterol (T‐CHO), and glucose (GLU) levels of juvenile bighead carp ( p < 0.05). The malondialdehyde (MDA) level was significantly lower than the control group when choline chloride supplementation ranged from 6 to 10 g/kg. When choline chloride supplementation was at 6 g/kg, the activities of catalase (CAT) and superoxide dismutase (SOD) were significantly higher than the control group ( p < 0.05). The levels of choline chloride supplementation (6–10 g/kg) increased the activity of intestinal digestive enzymes and enhanced the intestinal digestibility of juvenile bighead carp ( p < 0.05). In addition, choline chloride levels did not affect the abundance of intestinal microbiota, and the composition of the dominant phylum genera was similar, including Ascomycetes, Actinobacteria, and thick‐walled bacteria. At the genus level, there are Gemmobacter, ZOR0006, Peredibacter, and Mycobacterium, respectively. Overall, choline chloride supplementation (4–10 g/kg) could significantly improve the growth performance, antioxidant capacity, and digestive enzyme activity of juvenile bighead carp. Furthermore, broken‐line regression analysis has identified 6.51 and 6.62 g/kg as the optimal levels of dietary choline chloride for juvenile bighead carp based on growth performance. Overall, appropriate dietary choline chloride could improve growth performance, antioxidant capacity, and intestinal function in bighead carp.

To investigate dietary calcium requirement of bighead carp (Aristichthys nobilis), six purified diets were formulated to contain different concentrations of calcium (0.09% (control), 0.43%, 0.76%, 1.12%, 1.44%, and 1.79% of dry diets). Each diet was hand-fed to triplicate 30 fish with an average initial body weight (3.31 ± 0.09 g) for 60 days. The results showed that weight gain (WG) and specific growth rate (SGR) significantly increased when dietary calcium level was from 0.09% to 0.76% (P < 0.05). The phosphorus and calcium contents of whole fish body were highest in the 0.76% and 1.12% group, respectively (P < 0.05). The serum phosphorus content in the 1.79% group was significantly lower than those in other groups (P < 0.05). As dietary calcium content was from 0.09% to 0.76%, the activities of lipase and proteinase in the intestine had a significant increase (P < 0.05), while the glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) activities were significantly decreased (P < 0.05). Based on quadratic curve model analysis with WG and WGR as the appraising criteria, the appropriate dietary requirement of calcium for the bighead carp larvae (3.31 ± 0.09 g) was 1.01% - 1.02%.