This study explores the potential of high inclusion of an alkaline pre-treated Gelidium corneum solid by-product (GBP) obtained from the agar extraction industry, both alone and in combination with exogenous enzymes, on digestibility and fish faecal physical properties, aimed at tailoring RAS aquafeed for European seabass. Overall, 15% dietary inclusion of GBP did not affect energy, macronutrients, and amino acids digestibility, whereas supplementing the GBP-based diets with 2% of a carbohydrase enzyme complex enhanced the NDF digestibility. In addition, diets containing GBP improved faecal characteristics. Given the importance of water quality management in RAS, these findings suggest that incorporating low-cost by-products, such as GBP, into aquafeeds may optimise waste management and increase the economic sustainability of closed systems. Further studies should assess the impact of dietary GBP inclusion on fish growth, health, and water quality, while optimising aquafeed formulations for different farming conditions to enhance resource efficiency.
Valorisation of Agar by-products in European seabass (Dicentrarchus labrax) diets: a biocircular approach to otimise waste management in recirculating aquaculture
Fanizza C.
;Trocino A.;
2025
Abstract
This study explores the potential of high inclusion of an alkaline pre-treated Gelidium corneum solid by-product (GBP) obtained from the agar extraction industry, both alone and in combination with exogenous enzymes, on digestibility and fish faecal physical properties, aimed at tailoring RAS aquafeed for European seabass. Overall, 15% dietary inclusion of GBP did not affect energy, macronutrients, and amino acids digestibility, whereas supplementing the GBP-based diets with 2% of a carbohydrase enzyme complex enhanced the NDF digestibility. In addition, diets containing GBP improved faecal characteristics. Given the importance of water quality management in RAS, these findings suggest that incorporating low-cost by-products, such as GBP, into aquafeeds may optimise waste management and increase the economic sustainability of closed systems. Further studies should assess the impact of dietary GBP inclusion on fish growth, health, and water quality, while optimising aquafeed formulations for different farming conditions to enhance resource efficiency.
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