Effects of a low-fishmeal diet on growth performance in Penaeus vannamei cultured in a biofloc system in the Kuwait desert

Biofloc technology (BFT) offers a sustainable aquaculture strategy by generating high-quality microbial protein in situ, thereby reducing dependence on fishmeal in aquatic feeds. This study aimed to develop and evaluate a low-fishmeal diet for juvenile Pacific white shrimp (Penaeus vannamei) reared under BFT conditions using low-salinity groundwater in Kuwait. Two experimental diets were formulated to contain 20% (FM20) and 10% (FM10) fishmeal. Juveniles with an average initial weight of 0.44 ± 0.01 g (mean ± SEM) were stocked into six circular polyethylene tanks at a density of 200 individuals per tank. During the 8-week feeding trial, water quality parameters remained consistent across treatments. Growth performance and feed utilization indicators, including total production (TP), yield (Y), average daily growth (ADG), protein efficiency ratio (PER), feed conversion ratio (FCR), survival rate (SR), and condition factor (CF), did not differ significantly between treatments. However, shrimp fed the FM20 diet achieved significantly higher final body weight (FBW), weight gain (WG), specific growth rate (SGR), and feed efficiency (FE). Whole-body proximate analysis revealed significantly greater protein and lipid contents and lower moisture content in the FM20 group. Although amino acid profiles showed no significant differences, FM10-fed shrimp exhibited higher levels of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA), and lower levels of polyunsaturated fatty acids (PUFA). Essential fatty acids (EFA), including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), were significantly elevated in the FM20 group, whereas arachidonic acid (ARA) was lower. Among plasma metabolites, shrimp receiving the FM20 diet had significantly higher total protein (TP) and glucose (GLU) concentrations. No significant differences were observed for glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), total cholesterol (TCHO), triglycerides (TG), or plasma ion concentrations (Na+, K+, Cl–). These findings indicate that a 10% fishmeal diet can be used for juvenile P. vannamei cultured in a BFT system with low-salinity groundwater under desert aquaculture conditions, without compromising water quality or osmoregulatory function. However, further reduction in fishmeal may affect growth, nutrient deposition, and key physiological parameters.