Determine optimal levels of fishmeal/fish oil replacement with soy products (soybean meal, soybean oil and soy protein concentrate) in practical feeds for Gilthead sea bream (Sparus aurata)
A feeding trial with Gilthead seabream, the main species of marine fish produced in the Mediterranean region (>120 000 MT per year) was performed to evaluate the effect of different inclusion levels of soybean products (defatted soybean meal, soybean protein concentrate and soybean oil) as fish meal/oil replacement. The inclusion levels of soybean products were 18% for the control diet (high quality feed with 65% of the protein originating from fishmeal), 31-34% for the treatments with 50% of the protein coming from fishmeal and up to 46% for the treatments where only 35% of the protein was provided by fishmeal. Dietary formulation was adapted to compensate for effects of soybean inclusion on nutritional and palatability characteristics of the feeds.
Seabream were fed the experimental feeds during 8 weeks and parameters followed included growth, survival, food conversion, protein efficiency ration, carcass composition, filet composition, hepatosomatic and viscerosomatic indices, filet index, liver composition and gut histology.
Results indicated that none of the evaluated parameters was significantly affected by the different replacement levels compared to the control. Neither growth nor food conversion were affected by the inclusion of high levels of soybean products. Histological study of the intestinal epithelium did not show any pathological sign due to the replacement. It can be concluded that for Gilthead seabream, the replacement of fish meal with soybean meal under the conditions of the trial, is perfectly feasible without affecting the performance of the fish during the culture.