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Two feeding experiments were conducted to develop non‐fish meal and non‐fish oil diet for yellowtail with plant protein sources and Schizochytrium meal. For the first experiment, three iso‐nitrogenous and iso‐lipidic diets were prepared. Control diet was composed with fishmeal and fish oil and the other diet was formulated with plant protein sources and fish oil [FO]. Fish oil in FO diet was totally substituted by rapeseed oil and Schizochytrium sp., which was rich in DHA [NFO1]. Duplicate groups of yellowtails (Seriola quinqueradiata, 190.6 g) were fed the diets for 99 days. NFO1 group showed the lowest palatability and growth. However, fatty acid profile of NFO1 group showed the similar trend to FO. Four non‐fish meal diets were prepared for the second experiment with increased amount of feed attractant. 100FO diet was formulated similar to FO diet in the first experiment though higher amount of bonito peptide was contained. The other diets gradually employed Schizochytrium meal to substitute fish oil in 100FO diet for 35, 70 and 100%, respectively [65FO, 30FO, NFO2]. Duplicated groups of yellowtails (186.0 g) were fed the diets for 84 days. The growth result was improved by increasement of bonito peptide; however, it was inversely proportional to employment rate of algae meal. The results suggest possibility for developing non‐fish meal diet for yellowtail with plant protein sources and Schizochytrium sp. by inducing enough amount of feed attractant. Moreover, it needs further study on essential fatty acid utilization for yellowtail while developing non‐fish meal and non‐fish oil diet with microalgae. [ABSTRACT FROM AUTHOR]

A feeding experiment was conducted to determine the optimal formulation level of algae meal, which is rich in docosahexaenoic acid (DHA), in a non‐fish meal diet. Six iso‐nitrogenous (450 g/kg) and iso‐lipidic (130 g/kg) experimental diets were prepared. The control diet was formulated with fish meal (400 g/kg), fish oil (60 g/kg), plant protein sources (220 g/kg) and rapeseed oil (50 g/kg). Plant protein sources (soy protein concentrate, soybean meal and corn gluten meal), rapeseed and fish oil were formulated in the second diet (NFM + FO). In the third diet, fish oil of the NFM + FO diet was replaced by rapeseed oil (NFM + NFO) and designated as the negative control. In the other three diets, rapeseed oil in the NFM + NFO diet was replaced with algae meal (Schizochytrium sp. powder) at 50 g/kg, 100 g/kg and 150 g/kg (AM5, AM10 and AM15, respectively). Triplicate groups of juvenile red sea bream (8.8 g) were fed the experimental diets for 12 weeks near satiation. The growth was lowest in the fish fed NFM + NFO diet. This was improved by the formulation of algae meal, which reached the growth level of the NFM + FO group in the AM10 group. The lipid content of the whole fish body in the NFM + NFO group was significantly lower than those of other groups. The fatty acid profile showed significant differences among dietary treatments. DHA content in total and polar lipids of the whole body and liver was highest in the AM10 and AM15 groups. These results reconfirm that microalgae are a suitable lipid source for the replacement of dietary fish oil for marine fish, and the optimal level was estimated as 50 g/kg−100 g/kg in diet. [ABSTRACT FROM AUTHOR]