Exploring Palmaria palmata as a dietary ingredient for European sea bass (Dicentrarchus labrax) juveniles

Abstract

The red macroalgae Palmaria palmata is rich in protein and bioactive compounds and has been identified as a promising dietary ingredient for aquafeeds, with the potential to partially replace selected plant-based feed components. A digestibility trial and a growth trial were conducted to evaluate the potential of untreated and pretreated P. palmata as feed ingredients for juvenile European seabass ( Dicentrarchus labrax ), with initial body weights of 63.2 g and 38.0 g, respectively. Five diets were formulated: a control diet without macroalgae, and four diets including either 7.5% or 15% of untreated and pretreated P. palmata , replacing plant ingredients. The apparent digestibility coefficients of dry matter, crude protein, lipids, and gross energy did not differ among diets. The dietary inclusion of up to 15% P. palmata significantly increased the growth performance and feed efficiency compared to the control diet, without affecting nutrient digestibility, digestive enzyme activities, plasma metabolites, or whole-body composition of the fish. The pretreatment applied to P. palmata significantly increased soluble protein content and decreased neutral detergent fiber, but did not further improve growth or feed efficiency. Overall, these results indicate that up to 15% P. palmata can be successfully incorporated into the diets of juvenile European seabass, improving growth performance without adverse effects on nutrient digestibility. Further work is required to evaluate the functional properties and implications for fish health of P. palmata as well as to assess its economic viability within commercial aquafeed formulations.

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