Compound acidifier promoted the growth of hybrid grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatu) after high replacement of fish meal with cotton protein concentrate (CPC), improved stomach formation and digestibility, immune potency

Hybrid grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatu) is a popular aquaculture species in recent years. The latest research has found that cottonseed protein concentrate (CPC) has been found to be an effective alternative to fishmeal in feed production, but high substitution rates could cause growth inhibition and organism damage in hybrid grouper. Compound acidifiers in previous studies could effectively enhance the growth and digestive performance of fish. Therefore, five isonitrogenous (50% crude protein) and isolipid (10% ether extract) diets were used: a reference diet (FM, 50% fishmeal) and four experimental diets (27.5% fishmeal, 27.27% CPC) containing acidifiers at 0%, 0.05%, 0.1%, and 0.2%, respectively. There were three replicates of 30 groupers per group and the experiment lasted for 8 weeks. The results showed a significant increase in WGR and SGR and a significant decrease in FCR with the addition of 0.05% acidifier (P