Full replacement of fishmeal by poultry by –product meal in rainbow trout, Oncorhynchus mykiss (Walbaum, 1972) diet

Along the plant ingredients, rendered animal protein sources such as blood meal, meat and bone meal and poultry by-product meal have potential to be replaced by fishmeal in rainbow trout feed. Therefore, the main objective of the present study is to determine the effect of full replacement of fishmeal by poultry by-products meal (PBM) on fish performance, nutrient digestibility and also liver characteristics in rainbow trout. Four experimental diets were formulated to contain graded levels of PBM at 0 (control diet), 33 (PBM33), 66 (PBM66) or 100% (PBM100), respectively. The four treatments were randomly assigned to each of 12 tanks, having three replicates for each treatment. Rainbow trout juveniles with an average initial weight of 50±0.42g were reared for two months. The fish gained lower weight and specific growth rate at PBM 66% and 100%. FCR was recorded larger for rainbow trout feeding on PBM 66% and 100% in comparison to PBM 33% and control diets (p < 0.05). The whole exchange of fishmeal by PBM (PBM100%) reduced dry matter, fat and protein digestibility (p < 0.05). An increase in PBM content of diet also resulted in larger fat content of the fish liver (p < 0.05). Body fat content reduced and moisture content increased by increasing PBM level (p < 0.05). In conclusion, PBM can be included in rainbow trout feed as an alternative for fishmeal up to 33%. A larger fat content of liver at PBM 100% may indicate a negative impact of PBM on rainbow trout health at full replacement level.