Biofloc Meal-based Diets Enhance Immunostimulatory Activity and Survival of Penaeus vannamei Against Vibrio harveyi

Abstract

Vibrio harveyi (V. harveyi) is a major bacterial pathogen that significantly impacts shrimp cultivation. This study aimed to evaluate the potential of bioflocs, harvested from shrimp pond systems, as a fishmeal substitute to combat V. harveyi infection in shrimp Penaeus vannamei (P. vannamei). Shrimp were fed with 6 diet formulations: Four experimental diets in which fishmeal was replaced with biofloc meal at 25, 50, 75 and 100 % (designated B25, B50, B75, and B100, respectively), a fishmeal-based control diet without biofloc (B0), and a positive control diet supplemented with β-glucan (BG). Feeding trials were conducted for 30 days, followed by a challenge with V. harveyi. Growth performance, survival rates, total hemocyte count (THC), phagocytic activity, and histopathological changes were evaluated. The results demonstrated that all biofloc-fed groups had growth performance comparable to the B0 and BG groups. Shrimp fed with the B25, B50, and B75 diets exhibited significantly enhanced immune responses, with elevated THC and phagocytic activity. In the V. harveyi challenge, the B25 group showed the highest survival rate among biofloc diets, comparable to that of the BG group. Histological analysis revealed that B25 and B50 diets reduced hepatopancreatic and muscle damage associated with infection. In conclusion, this study provides evidence that substituting fishmeal with biofloc (25-50 %) effectively enhances immune function and confers protection against V. harveyi infection in P. vannamei, supporting its potential as a sustainable functional feed ingredient in shrimp aquaculture.