Evaluation of flesh quality and antioxidant responses in grow-out largemouth bass (Micropterus salmoides) with novel protein substitutes

The present research evaluated the impact of various novel protein sources, including Tenebrio molitor (TM), cottonseed protein concentrate (CSM), Clostridium autoethanogenum (CAP), and Chlorella vulgaris (ChM), on the muscle traits of grow-out largemouth bass. Fish (211.9 ± 1.2) g were fed five meals for eight weeks. Dietary protein sources significantly influenced growth performance and feed utilization. The fishmeal (FM) group exhibited the highest final body weight, feed conversion ratio (FCR), and protein efficiency ratio (PER). In contrast, alternative protein diets, particularly TM, CSM, and CAP, resulted in reduced growth and feed efficiency. The ChM group showed a comparable final weight to fishmeal (FM), though with slightly lower feed efficiency. Muscle antioxidant profiles demonstrated stable SOD activity ( P > 0.05) among groups, while the ChM diet increased GSH-Px activity ( P < 0.05), and the CSM diet elevated MDA levels ( P < 0.05). The muscle texture analysis revealed initial reductions in hardness, gumminess, chewiness, and tenderness, followed by improvements across protein sources. Protein sources modified the amino acid profile without affecting fatty acids. The ChM group had a higher unsaturated fatty acids (UFA)/saturated fatty acids (SFA) ratio than FM, with no significant changes in UFA or SFA levels ( P > 0.05). TM groups had lower n-3 PUFA content than FM ( P < 0.05), and ChM had higher n-6 PUFA content than FM ( P < 0.05). Novel proteins reduced the n-3/n-6 PUFA ratio than FM ( P < 0.05) with no differences among treatments ( P > 0.05). The novel protein groups also had a significantly lower n-3/n-6 PUFA ratio than FM ( P < 0.05). The transcript analysis indicated that the ChM group upregulated the expression of myf5, myod, and myog , while the diets downregulated the expression of mstn . The z-score analysis indicated that ChM is the most valuable for muscle texture and growth. The results indicated that ChM and other innovative diets can enhance muscle quality and aquaculture productivity.