Influence of dietary levels of soybean meal on the performance and gut histology of gilthead sea bream (Sparus aurata L.) and European sea bass (Dicentrarchus labrax L.)

The present studywas performed to determine the effect of soybean meal (SBM) on the performance and gut histology of gilthead sea breamand European sea bass. Three isonitrogenous and isolipidic extruded diets (crude protein, 470 g kg1 diet; crude fat, 200 g kg1 diet) were formulated containing 0 (0 SBM), 180 (180 SBM) and 300 (300 SBM) g kg1 diet SBM and tested on both species in two separate experiments. Fish at an initial average weight of around18 g were randomly allocated to 800 L square tanks connected to a closed recirculating system.The trials lasted 80 days for sea breamand 89 days for sea bass. Fish were hand-fed to apparent satiation. Increasing the level of SBM had no signi¢cant e¡ects on the speci¢c growth rate, feed intake and feed conversion rate in both the species. In the sea bream distal intestine, lamina propria was moderately and di¡usely expanded in some ¢sh due to an increase in cell in¢ltration represented by mononuclear cells, this ¢nding being more frequent in animals fed diet 300 SBM. No other morphological alterations in intestinal folds, enterocytes or other in£ammation signs were noticed in the sea bream distal intestine of any group. No histological di¡erences were found in sea bass in any experimental group.