Replacing fishmeal with fermented soybean meal in the diets of tiger puffer (Takifugu rubripes): Effects on growth performance, antioxidant and immunity capacity and flesh quality based on metabolomics

This study investigated the effects of partially substituting fishmeal (FM) with fermented soybean meal (FSM) on the growth performance, liver and serum biochemical, flesh quality and metabolomics of tiger puffer (Takifugu rubripes). Five diets with FSM supplementation to replace 0 (control, FM), 15 % (FSM15), 30 % (FSM30), 45 % (FSM45) and 60 % (FSM60) FM were used to feed tiger puffer (39.6 ± 0.2 g) for 60 days. The results indicated that FSM could effectively replace up to 30 % of FM in diets without adverse impacts on weight gain (WG) and feed conversion ratio (FCR). In contrast, WG declined by 17.7 % and 33.6 %, and FCR increased by 0.22 and 0.55 in the FSM45 and FSM60 groups, respectively (P < 0.05). Compared to FM group, the contents of total fatty acids (TFA), C16:0, C22:6, total amino acids (TAA), Val, Ile and the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) in flesh were significantly decreased, while the contents of collagen in flesh and alkaline phosphatase (ALP) in serum were significantly increased in FSM60 group (P < 0.05). In addition, FSM45 and FSM60 groups exhibited significantly higher the contents of total free amino acid (TFAA), flavor amino acid (FAA), Glu, Gly and Cys in flesh and alanine aminotransferase (ALT) in serum and lower liver cholesterol (CHO) levels compared to FM group (P < 0.05). 157 and 190 named metabolites were identified in FSM30 and FSM60 groups, respectively, compared to the control, and these metabolites were primarily involved in “lipid metabolism” and “amino acid metabolism”. In summary, in a diet containing 450 g/kg FM, FSM could replace FM up to 30 % without compromising the growth, serum and liver biochemical, flesh amino acids and fatty acids of tiger puffer. The optimum replacement level of FM with FSM was 31.79–32.48 % by broken-line based on WG and FCR.