Effects of Dietary Copper on Growth Performance, Immune Responses and Intestinal Microbiome in Sub-adult Crayfish (Procambarus clarkii)

Abstract This study investigates the optimal dietary copper levels for Procambarus clarkii, examining its impact on growth, immune responses, and gut microbiota in an indoor aquaculture setting to improve feed formulations. In a 7-week study, P.clarkii (initial weight 13 ± 0.01g) was fed five different diets with varying copper levels. A control group (Cu0, 1.48 mg Cu/kg) was compared to four experimental groups (Cu15, Cu30, Cu60, Cu120) containing 12.72, 27.71, 65.09, and 121.34 mg Cu/kg, respectively, added as copper sulfate pentahydrate (CuSO₄·5H₂O). 375 crayfish were divided into five groups in 3 replicates with 25 crayfish in each pond. Specifically, the FBW (Final Body Weight), SGR (Specific Growth Rate) and WGR (Weight Gain Rate) of the Cu30 group was significantly higher, and the FCR (Feed Conversion Ratio) and MR (Meat Rate) were significantly lower than those of the other groups (P < 0.05). Compared with the control group, the copper content in the crayfish of the group of the Cu60 and Cu120 was significantly increased (P < 0.05). The AST (Aspartate Aminotransferase) level in hemolymph biochemical of the Cu120 group was the highest and lowest Cu30 group (P < 0.05). The antioxidant showed that the content of ceruloplasmin (CP) in the hepatopancreas increased with the increase of copper addition, and the contents of total superoxide dismutase (T-SOD), copper/zinc superoxide dismutase (Cu/Zn-SOD) and glutathione (GSH) of the Cu30 group was significantly higher than other groups (P < 0.05). Compared with other groups, the MDA (Malondialdehyde) content of Cu30 and Cu60 groups was significantly lower (P < 0.05). Cu concentration did not affect overall microbial diversity but altered the gut microbiota composition. High copper (Cu120) significantly decreased Proteobacteria, Anaerorhabdus furcosa, Erysipelatoclostridium, Dysgonomonas, and ZOR0006, while increasing Verrucomicrobiota and Nitrospirota. This suggests high copper can disrupt gut microbial balance. In addition, the optimal dietary copper requirement of P.clarkii was determined to be between 46.24–47.86 mg/kg through the quadratic regression analysis of weight gain rate (WGR) and specific growth rate (SGR).