Dietary enzyme complex improve the growth performance, digestive ability, antioxidant capacity and immunity, and glycometabolism in Penaeus vannamei fed high-plant-protein diets

In this study, six isonitrogenous and isolipid diets were formulated. A diet containing 12 % fishmeal was used as the fishmeal control group (PC). By using composite plant protein sources (soybean meal, peanut meal, and low-gossypol cottonseed meal) to partially replace fishmeal, a high-plant-protein diet with 4 % fishmeal was formed. In these high-plant-protein diets, 0 %, 0.02 %, 0.04 %, 0.06 %, and 0.08 % enzyme complex preparations (EC) were added and named NC, NCA2, NCA4, NCA6, and NCA8, respectively. The results showed that compared to the PC group, the NC diet significantly reduced the growth performance of white shrimp, which was notably improved after adding EC (WGR, FE, and SGR were significantly increased). Additionally, compared to the NC group, dietary EC significantly improved the antioxidant capacity and immunity of shrimp, enhanced the activities of plasma SOD, LZM, PO, and T-AOC, and the expression of CAT, SOD, GST, and GPx genes in the hepatopancreas. Compared to the NC group, the addition of EC also significantly improved the digestive capacity of the shrimp, with a significant increase in hepatopancreatic Try activity and the expression of Amy and Try genes, as well as a clear upward trend in the apparent digestibility of dry matter and crude protein. The plasma Glu concentration in the NC group was significantly lower than that in the PC and the EC added group. The dietary EC significantly increased the activities of key glycolytic enzymes HK, PK, and PFK in the hepatopancreas of white shrimp, and significantly upregulated the gene expression of HK, PK, and GLUT2 in the hepatopancreas. Furthermore, when compared to the NC group, EC diets notably decreased the activities of the key gluconeogenesis enzymes G6P and PEPCK in the hepatopancreas of white shrimp. Additionally, these diets significantly increased the gene expression of PC and PEPCK in the hepatopancreas of white shrimp. The optimal supplemental level of EC was 0.030–0.031 % by quadratic equation fitting of WGR, SGR, and FE with the dietary supplemental level of EC. In summary, dietary EC supplementation significantly enhanced the utilization of high-plant-protein diets by white shrimp, with the optimal addition amount being 0.030–0.031 % under the conditions of this trial.