Effects of Dietary Curcumin Supplementation Under High-Level Fishmeal Replacement with Clostridium autoethanogenum Protein in Penaeus vannamei: Growth Performance, Immunity, Intestinal Health, and Transcriptome Responses

Clostridium autoethanogenum protein (CAP) offers a sustainable fishmeal alternative, but high inclusion may impair shrimp growth and health. This study evaluated the responses associated with dietary curcumin (CUR) supplementation in Penaeus vannamei fed a diet in which 50% of the fishmeal was replaced with CAP. Three diets were formulated: a fishmeal-based control diet (FM), a low-fishmeal diet in which 50% of the fishmeal was replaced with CAP (CAP), and the CAP diet supplemented with 60 mg/kg CUR (CTER). After an 8-week feeding trial, P. vannamei fed the CAP diet exhibited significantly lower final body weight, weight gain rate, and specific growth rate, accompanied by adverse histological changes in the intestine and hepatopancreas, reduced hepatopancreatic immune enzyme activities, and alterations in the intestinal microbiota. Compared with the CAP group, CUR supplementation was associated with improved growth performance, higher survival following WSSV exposure, improved hepatopancreatic and intestinal morphology, increased immune enzyme activities, greater microbial richness, and shifts in the relative abundance of several dominant bacterial taxa. Transcriptomic analysis further suggested that the beneficial effects of CUR may be partly associated with differential expression of genes enriched in metabolism- and immunity-related pathways. Overall, dietary CUR supplementation was associated with broad improvements in growth, tissue condition, nonspecific immune responses, intestinal microbial profiles, and post-challenge survival under the high-CAP dietary condition. These findings support the potential application of CUR as a functional additive in CAP-based, low-fishmeal diets for P. vannamei.