Substitution of fishmeal with Clostridium autoethanogenum protein in pearl gentian grouper (♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatus) diets: Effects on growth performance, feed utilization and flesh quality

This study evaluated the effect of replacing dietary fishmeal with Clostridium autoethanogenum protein (CAP) on growth performance, feed utilization and flesh quality of pearl gentian grouper (♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatus ). A basal diet with 400 g/kg of fishmeal was formulated as the control diet (CAP0), and then 15 % (CAP15), 30 % (CAP30), 45 % (CAP45) and 60 % (CAP60) of dietary fishmeal were replaced by CAP. The five diets were fed to pearl gentian grouper with initial body weight of 90.4 g for 12 weeks. Results showed that weight gain (WG) and feed intake (FI) were linearly and negatively correlated with dietary CAP, and CAP60 group exhibited lower WG and FI than CAP0 group ( P < 0.05). Flesh hardness and shear force showed both linear and quadratic trends with dietary CAP levels, with the lowest values recorded in CAP60 group ( P < 0.05). CAP60 group exhibited higher muscle fiber density and smaller fiber diameter than CAP0 group ( P < 0.05). Serum glucose (GLU) and triglyceride (TG) levels increased linearly with dietary CAP levels, while serum cholesterol (CHO) level and flesh total antioxidant capacity (T-AOC) level exhibited both linear and quadratic trend ( P < 0.05). In conclusion, CAP can replace up to 45 % (180 g/kg) of dietary fishmeal without negative effects on growth performance, feed utilization, flesh composition, texture, muscle fiber morphology and antioxidant capacity, but 60 % (240 g/kg) of fishmeal replacement with CAP decreased growth and flesh quality of pearl gentian grouper. • Clostridium autoethanogenum protein could replace 45 % dietary fishmeal (180 g/kg) for pearl gentian grouper. • High fishmeal replacement (≥ 60 %) by CAP decreased growth performance and flesh quality. • The decreased flesh hardness was associated with the decrease of muscle fiber diameter.