Finding inexpensive and high-quality protein sources to replace fish meal is currently a thorny issue for the feed industry due to the decline in fishery resources and the increased demand for fishmeal, which has led to a significant increase in fishmeal prices. In this study, we selected five new non-grain protein sources, Clostridium autoethanogenum
protein (CAP), Chlorell
meal (CM), Hermetia illucens
meal (HM), Tenebrio molitor
meal (TM), and cottonseed protein concentrate (CPC). This study was conducted to evaluate the apparent digestibility of dry matter, crude protein, crude lipid, gross energy, and amino acid of these five protein sources by large yellow croakers (Larimichthys crocea
) to provide a theoretical basis for the design of artificial compound feed formulations for large yellow croakers. Triplicate groups of fish initial weight=(154.0±5.3)g were fed the test diets to apparent satiation two times daily for eight weeks. The test diets consisted of 70% basal diet and 30% test ingredients, and 0.1% yttrium oxide (Y2
) was used as an indicator. The results showed that dry matter coefficients of five test ingredients ranged from 56.77% to 75.53%(CAP>TM>CM>HM>CPC); The apparent digestibility of the crude protein ranged from 69.93% to 89.59%(CAP>CM>CPC>HM>TM); The apparent digestibility of crude lipid ranged from 58.58% to 93.77%(CAP>CM>TM>CPC>HM); The apparent digestibility of the gross energy ranged from 63.39% to 84.33%(CAP>HM>CM>TM>CPC); The apparent digestibility of the total amino acids ranged from 76.62% to 93.24%(CAP>CM>CPC>HM>TM). In conclusion, CAP is the optimum protein source of the five ingredients. However, CM, TM, and CPC require supplementation of deficient nutrients in their diets, and HM involves the addition of a defatting process to improve raw material nutrient levels. Additionally, comparative feeding experiments are required to determine the optimum amount of these five protein sources to be added to the large yellow croaker feed.