Effects of dietary plant-protein sources intake on growth, digestive enzyme activity, edible tissue nutritional status and intestinal health of the omnivorous Redclaw crayfish, Cherax quadricarinatus .

For omnivorous crayfish, plant raw materials can be good alternatives to dietary fish meal for the Redclaw crayfish Cherax quadricarinatus . A 56-day feeding trial was conducted in C. quadricarinatus (11.70 ± 0.13 g) fed with eight diets. Diet with 100% fish meal (FM) as the protein source was the control. Seven experimental diets were formulated by replacing 75% or 100% of FM with soybean meal (SM75, SM100) or cottonseed meal (CM75 and CM100), and a mixture of SM and CM (protein content is 1:1) replacing 50%, 75% or 100% of FM (SC50, SC75, and SC100). Crayfish fed the CM100 and SC100 showed significantly lower WG, SGR, trypsin and pepsin activities compared to control diet. Crayfish in CM100 group showed significantly higher GPx, ALT, AST activities and MDA content than the control. SM100 and CM100 diets can cause slight separation of the peritrophic membrane from the intestinal folds. The pepsin activity of crayfish in SC50 were significantly higher than those in other experimental diets. The highest WG and muscle arginine content were also found in crayfish fed SC50. The relative abundance of Proteobacteria phylum, Unclassified Enterobacteriaceae , and Candidatus Bacilloplasma was significantly higher, but the relative abundance of Actinobacteriota phylum was significantly lower in crayfish fed SM100, CM100, and SC100 than those in control. Microbiota functional prediction indicated that the relative abundance of "cell motility" pathway in crayfish fed CM100 was significantly decreased compared to control. In conclusion, only half of the fish meal can be effective substituted with a mixture of soybean meal and cottonseed meal (protein content is 1:1) for C. quadricarinatus .