Introduction
As global shrimp aquaculture continues to expand, the industry faces increasing pressure to develop sustainable rearing systems that optimize feed efficiency and reduce environmental impact. While Recirculating Aquaculture Systems (RAS) are widely utilized for their high level of biosecurity and environmental control, Biofloc Technology (BFT) has emerged as a promising alternative, leveraging dense microbial communities to recycle nitrogenous waste into supplemental "in situ" nutrition . Despite the known growth benefits of biofloc, the extent to which these systems influence the metabolomic status of whiteleg shrimp (Litopenaeus vannamei) remains poorly characterized. Understanding these shifts is crucial for improving husbandry protocols and final product quality; a useful tool to study the metabolome in relation to diverse dietary regimes is 1H-NMR . Using this approach, the goal of this study was to compare the growth performance and tissue-specific 1H NMR metabolomic profiles of whiteleg shrimp reared in RAS vs. BIOFLOC systems under restricted feeding conditions, providing novel insights into the nutrient utilization and metabolic adaptation in intensive culture.
Materials and Method
Whiteleg shrimp (14.23 ± 0.51 g) were reared for 70 days in two distinct systems: a traditional Recirculating Aquaculture System (RAS) and a Biofloc-based system (BIOFLOC). Stocking density was maintained at 100 individuals m-3 across triplicate. While the RAS group was fed a standard commercial diet following the producer's indication at a 2.8% daily feeding rate, the BIOFLOC group received a 20% restricted ration to account for the nutritional contribution of biofloc aggregates. Growth performance and feed efficiency were evaluated. At the conclusion of the trial, aqueous and lipid fractions of the muscle and hepatopancreas were extracted and analyzed using 1H-NMR spectroscopy . Multivariate statistical analysis (PCA and OPLS-DA) was then applied to evaluate potential differences in metabolic profiles and identify specific biomarkers.
Results
Survival and growth indicators (FBW, WG, and SGR) did not differ significantly between treatments, with survival exceeding 92% in both groups. However, feed efficiency was significantly improved in the BIOFLOC group, which exhibited a lower apparent feed conversion rate (A-FCR: p = 0.023) despite a 20% reduction in administered feed. Multivariate statistical analysis of 1H-NMR spectra revealed distinct metabolomic signatures between the two systems, (OPLS-DA models; Q2 > 0.85). In the muscle extracts, BIOFLOC shrimp showed higher relative concentrations of specific amino acids (leucine, phenylalanine, arginine), 2-hydroxybutyrate, saturated FAs and phospholipids. Conversely, this group exhibited lower levels of glutamate, glycine, lactate, TMAO and unsaturated FAs compared RAS group. On the other hand, BIOFLOC hepatopancreas extracts showed a distinct shift characterized by increased in aspartate, 2-hydroxybutyrate, lactate, and unsaturated FAs, offset by lower levels of leucine, glycine, betaine, TMAO, choline, saturated FAs, and phospholipids (relative to RAS).
Discussion
This study confirms that biofloc technology can maintain growth performance when the feeding rate is reduced by 20%. The results also show that the different rearing methods caused a shift in the shrimp's compositional profile. The high levels of essential amino acids (leucine, phenylalanine, and arginine) in the muscle, confirms that BIOFLOC aggregates can serve as a high-quality supplemental "in situ" nutritional source. On the contrary, the elevated levels of glutamate and TMAO in RAS shrimp may suggest a greater reliance on specific osmoregulatory pathways or different nitrogenous waste processing compared to the BIOFLOC group. Furthermore, the divergence in lipid composition, specifically the higher accumulation of phospholipids and saturated fatty acids in BIOFLOC-reared shrimp, indicates a shift in lipid metabolism and membrane structural components influenced by the microbial community. These results highlight that BIOFLOC-based systems enhance nutrient utilization and alter the nutritional "fingerprint" of the final product.
Acknowledgments
Thanks to Chiara Roberta Girelli and Francesco Paolo Fanizzi, General and Inorganic Chemistry Lab, at DiSTeBA University of Salento, for metabolomic analysis. This study was co-funded under MEloDIZER (European Union's Horizon Europe programme G.A. 101091915) and BIORAS_SHRIMP (European Union's Horizon 2020 research and innovation programme, ERA-Net Cofund project BlueBio and Xjenza Malta. G.A. BLUE BIOECONOMY-2021-02).
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