Total Replacement of Fishmeal with Plant Sources in European Seabass (Dicentrarchus labrax): Growth Parameters, Nutritional Efficiency, Intestinal Health and Economic Profitability

The objective of this research was to evaluate the effects of different dietary fishmeal levels (30%, 15% and 0%) on growth, biometric parameters, nutritional efficiency, and intestinal health in juvenile European seabass. The replacement of fishmeal was made with a mixture of vegetable protein sources (soybean meal, wheat gluten, and wheat meal), and synthetic amino acids in isoproteic diets. The experimental period lasted 196 days, and the fish were fed the formulated diets twice a day, with an initial average weight of 40 g/fish. The results showed that it is possible to partially replace fishmeal with an inclusion level of 15% without compromising growth performance. However, the complete substitution of fishmeal resulted in increased viscerosomatic index (VSI) and mesenteric fat (MF), which was also associated with a pro-inflammatory response and moderate immunosuppression at the intestine level. Fish fed the 0 FM diet exhibited reduced growth, poor productive performance, and the lowest survival rates. Furthermore, the expression levels of Muc2 and β-actin genes, together with trends observed for TGF-β and IL-8, indicated impaired intestinal health and a pronounced immunosuppressive condition in these fish. Economic profitability was found to depend on the market prices of fishmeal and wheat gluten.