Replacing poultry by‐product meal protein with soybean protein isolate in low fishmeal diets for juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂)

A 7‐week growth trial was conducted to assess the potential of using soybean protein isolate (SPI) to replace poultry by‐product meal (PBM) protein in low fishmeal (FM) diets for juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂). Seven isoproteic (490 g kg−1) and isolipidic (90 g kg−1) experimental diets were formulated, including six low FM diets and a high FM diet (HFMP). The low FM diets contained 0, 74.8, 149.7, 224.5, 299.4 and 374.2 g kg−1 SPI, replacing approximately 0%, 20%, 40%, 60%, 80% and 100% of the PBM protein (designated as SPIP0, SPIP20, SPIP40, SPIP60, SPIP80 and SPIP100, respectively). Each diet was hand‐fed to triplicate groups of 12 hybrid grouper juveniles (average initial body weight: 14.30 ± 0.1 g per fish). After being fed for 7 weeks, fish fed with HFMP and SPIP60 showed significantly higher (p