The sustainability of shrimp aquaculture depends on reducing waste streams while identifying alternative functional feed ingredients that support animal health and performance. Within the C-SHRIMP project, a circular production concept was developed in which sludge generated from a recirculating aquaculture system (RAS) for Litopenaeus vannamei was recovered and upgraded into microbial protein (MP). Waste solids collected from the RAS were concentrated through improved sludge management and subsequently subjected to controlled fermentation, where microbial biomass converted the organic fraction into a protein-rich product. This approach transforms residual aquaculture waste into a valuable feed ingredient with both nutritional and potential immunostimulatory properties. Two MP products with differing protein quality and composition were obtained and subsequently evaluated in feeding trials with whiteleg shrimp Litopenaeus vannamei.
Dietary trials assessed different inclusion levels of both MP products in shrimp feed (between 0.2% and 10%) and their effects on growth performance, immune responses, and disease resilience. Growth-related parameters included survival, feed conversion ratio (FCR), weight gain, and overall production performance. Only minor differences in weight gain were observed at higher inclusion levels, while survival remained unaffected across treatments, indicating good dietary tolerance. Effects of both MP products were observed on multiple performance indicators, demonstrating their biological activity in practical feeding conditions.
To evaluate immunomodulatory potential, several innate immune parameters were measured after 7 and 14 days of feeding, including total haemocyte count (THC), differential haemocyte count (DHC), superoxide dismutase (SOD), and phenoloxidase activity (POA). Both MP products influenced these immune markers, with responses depending on sampling timepoint, inclusion level, product type, and feeding duration. Changes in haemocyte profiles and enzyme activity suggest that dietary MP can modulate shrimp innate immunity and may enhance physiological readiness against stress or infection.
Following 28 days of pre-feeding with MP-containing diets, shrimp were subjected to challenge tests with two major pathogens: White Spot Syndrome Virus (WSSV) and Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease (AHPND). These trials were conducted to assess whether the observed immune effects translated into improved disease resistance.
The results demonstrate that microbial protein derived from shrimp RAS waste can be successfully incorporated into shrimp diets without compromising growth performance, while providing measurable effects on immune status and potential health resilience. This highlights the dual value of MP as both a sustainable protein source and a functional feed ingredient, supporting circular and competitive shrimp aquaculture systems.
Acknowledgement
This research received funding (HBC.2022.0547) from Flanders Innovation and Entrepreneurship (Belgium).