Effects of dietary guava leaf aqueous extract supplementation on growth, antioxidant capacity, and non-specific immunity in mud crab Scylla paramamosain

Mud crab (Scylla paramamosain) fed five different diets with varying concentrations of guava leaf aqueous extract (0 mg center dot kg(-1), 80 mg center dot kg(-1), 160 mg center dot kg(-1), 320 mg center dot kg(-1), and 640 mg center dot kg(-1)) for 30 days. Mud crabs in the 320 mg center dot kg(-1) guava-leaf extract groups outperformed the control group in terms of survival rates (SR), weight gain rates (WGR), and specific growth rates (SGR). When compared to the control group, mud crabs in the 320 mg center dot kg(-1) guava-leaf extract groups had significantly higher levels of lipase (LPS), pepsin, lysozyme (LZM), superoxide dismutase (SOD), acid phosphatase (ACP), and glutathione (GSH) (P < 0.05). The amylase (AMS) activity was significantly decreased in all experimental groups (P < 0.05). Malondialdehyde (MDA) content in the hepatopancreas of mud crabs in the 160 mg center dot kg(-1), 320 mg center dot kg(-1), and 640 mg center dot kg(-1) guava-leaf extract groups were significantly reduced compared to the control group (P < 0.05). Additionally, real-time PCR results illustrated that the expression levels of GPx3, CAT, and JNK were all considerably increased in the 80 mg center dot kg(-1) guava-leaf extract groups compared to the control group (P < 0.05). In the 160 mg center dot kg(-1), 320 mg center dot kg(-1), and 320 mg center dot kg(-1) guava-leaf extract groups, the expression levels of SOD genes were considerably greater than the control (P < 0.05), which was consistent with the level of SOD activity. GST and P53 gene expression levels were significantly up-regulated in the 80 mg center dot kg(-1), 160 mg center dot kg(-1), 320 mg center dot kg(-1), and 640 mg center dot kg(-1) guava-leaf extract groups compared to the control group (P < 0.05). Overall, the addition of 160 mg center dot kg(-1)-320 mg center dot kg(-1) guava-leaf extract to the feed of Scylla paramamosain promoted growth, enhanced the activities of digestive and antioxidant enzymes, and strengthened immunity.