Effects of different levels of curcumin on growth, digestive enzymes, immunity and antioxidant indices of crayfish (Procambarus clarkii).

This study aimed to investigate the effects of dietary supplementation with different levels of curcumin on the growth performance, digestive enzyme activity, hemolymph immune parameters, and hepatic antioxidant function of crayfish (Procambarus clarkii). A total of 300 healthy crayfish (10.5 ± 1.0 g) were randomly divided into 5 treatment groups with 3 replicates each: Group 1 fed a basal diet (0 mg/kg group), Group 2 fed basal diet + 50 mg/kg curcumin (50 mg/kg group), Group 3 fed basal diet + 100 mg/kg curcumin (100 mg/kg group), Group 4 fed basal diet + 200 mg/kg curcumin (200 mg/kg group), and Group 5 fed basal diet + 300 mg/kg curcumin (300 mg/kg group) for 8 weeks. The results indicated that dietary curcumin supplementation significantly affected the weight gain rate and feed conversion ratio of crayfish. Specifically, the weight gain rate in the 100 mg/kg group was significantly higher than other treatment groups. Furthermore, different levels of curcumin significantly influenced the activities of protease, lipase, and amylase. The 100 mg/kg group exhibited significantly higher activities of these digestive enzymes compared to the other groups. The acid phosphatase activity in the 100 mg/kg group was extremely significantly higher than that in the 0 mg/kg group (P < 0.01). The complement C3 level in the 100 mg/kg group was extremely significantly higher than in other groups (P < 0.01). The complement C4 levels in the 100 mg/kg and 200 mg/kg groups were significantly higher than those in the 0 mg/kg group (P < 0.01), while the lysozyme activity in the 100 mg/kg group was extremely significantly higher than in the 0 mg/kg group (P < 0.01) and significantly higher than in other groups (P < 0.05). With increasing dietary curcumin levels, the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), and total antioxidant capacity (T-AOC) in the hepatopancreas of crayfish initially increased and then decreased, reaching their peak at 100 mg/kg curcumin supplementation, while the malondialdehyde (MDA) level in the hepatopancreas reached its minimum. Meanwhile, the activities of the antioxidant-related genes SOD, CAT, GPX, and the cytokines Keap1a and Nrf2 involved in the antioxidant response in the hepatopancreas of crayfish also showed an initial increase followed by a decrease, peaking at the supplementation level of 100 mg/kg curcumin. The study demonstrates that moderate dietary curcumin addition exerts multiple positive effects on crayfish: it not only significantly promotes growth and improves digestive efficiency but also effectively enhances antioxidant capacity and immune function. Among the tested levels, the 100 mg/kg supplementation yielded the most prominent improvements in antioxidant indices and immune parameters, indicating that this dosage is the optimal choice for promoting healthy crayfish cultivation and overall benefits.