Fish protein hydrolysates from rainbow trout processing in replacement of feed protein sources: Effects on growth performances, liver status and body composition of gilthead sea bream, Sparus aurata L., juveniles

The use of processing by-products may reduce pressure on fish stocks as well as diminish wastes and negative environmental impact. Different studies investigated fish by-products used as alternative nutritional source to conventional feedstuffs. Fish protein hydrolysates (FPH), as a protein source derived from discards of rainbow trout processing, were included in feeds and effects were evaluated on productive performances, liver status, and body composition in gilthead sea bream, Sparus aurata L., juveniles. Three groups of 170 juveniles each (initial weight 37.8 ± 0.5 g), in triplicate indoor tanks of 2 m³ volume each, were fed including FPH in L1 (7.5 g/kg) and L2 (15 g/kg) feeds in replacement of fishmeal. LC diet was used as control having fish meal and soybean meal as main protein sources. At the end of the trial (85 days), satisfactory productive performances were obtained in all the groups with similar performances. The final mean weight ranged from 76.6 to 78.0 g. The two FPH diets exhibited high palatability equal to LC. Liver histology did not differ although fat accumulation was detected in all fish. Body composition and fatty acids were similar. FPH as substitute of protein source is suitable in the feeding of gilthead sea bream juveniles.