The Pacific white-leg shrimp Litopenaeus vannamei is one of the most cultured species worldwide, thanks to its adaptability to environmental changes and omnivorous feeding behavior. However, ensuring sustainable growth of this industry demands continual screening for innovative aquafeed ingredients, given that the diet highly determines the animal’s physiology and the business’s profitability. Macroalgae have been proposed as a promising aquafeed ingredient for shrimp owing to their high content of bioactive compounds, appropriate nutritional composition, and cost-effective cultivation process. Their inclusion in diets would improve the growth performance of the shrimp, and change the microbiome composition. Moreover, studies have shown how the gut microbiota strongly influences the immune state of the animals through the direct competence of beneficial and opportunistic bacteria in the gut, keeping a healthy balance that prevents disease outbreaks. This research investigates the effect of macroalgae inclusion on the diet of juvenile L. vannamei in terms of growth performance and gut microbiome composition, in collaboration with the UGent Phycology lab.
This study evaluates the potential of a selection of green, red, and brown macroalgae: three species indigenous to the North Sea area (Fucus serratus, Chondrus crispus, and Ulva spp.) and two invasive macroalgae species (Sargassum muticulus and Gratelupia turuturu) were evaluated as sustainable aquafeed ingredient. Macroalgae were collected, rinsed, dried, grinded, and processed through cold extrusion into dry shrimp feed at an inclusion level of 5%. Liquid extracts were produced from the grinded seaweeds and screened in vitro for their antibacterial activity against the common shrimp pathogens Vibrio parahaemolyticus and V. harveyi. Juvenile L. vannamei (± 1g) were fed for 4 weeks with one of these test diets or a commercial one (control). Growth was monitored weekly and the feed conversion rate (FCR) and specific growth rate (SGR) were calculated. Shrimp were then sampled and their digestive tract was aseptically dissected for gut microbiome analysis in terms of relative abundance and richness. The nutritional and proximate composition of the macroalgae and the diets were assessed, as well as the whole-body composition of the shrimp at the start and the end of the study.
The study demonstrates the multifunctional benefits of macroalgae as aquafeed ingredients, serving as immunostimulants and nutritional supplements. Furthermore, utilizing invasive species in aquafeeds presents a dual advantage, offering a means of control while mitigating their adverse environmental impact on local ecosystems. Moreover, sustainable aquaculture practices are essential for the long-term viability of the industry, seeking to use components that have a production with a lower footprint than the traditional fish meal and oil ingredients needed for the production of carnivorous species. Seaweeds and shrimp are both low-trophic level species with short production cycles, and their integration in productive systems could be a strategy for environmental mitigation and food security efforts.