Proximate compositions evaluation, histology and transcriptome analysis revealed the effects of formulated diets on muscle quality in Micropterus salmoides

With the gradually upgrade of formulated feeds, the largemouth bass Micropterus salmoides has been domesticated to adapt to formulated diets to reduce the use of bait fish and cut cost. However, whether the formulated diets influence the nutritional content and muscle quality of largemouth bass and related mechanisms remains unclear. In this study, we evaluated the effects of forage fish and formulated diets on growth performance, proximate compositions, muscle histology and fiber character. Largemouth bass with initial weights of 39.37 ± 1.37g and 39.45 ± 1.40g were fed with formulated diets and forage fish for 8 months, respectively. The results showed that formulated diets group (FDG) exhibited higher levels of protein content and free amino acids compared with forage fish group (FFG). Interestingly, the diameter of muscle fiber was larger in FDG than in FFG through microsection observation. A comparative analysis of transcriptome was constructed for muscle tissues of FDG and FFG, respectively. Compared with FFG, 2186 differentially expressed genes (DEGs) were identified in FDG, including 1915 upregulated genes and 271 downregulated genes. Gene ontology (GO) analyses revealed that DEGs were significantly enriched in GO terms regarding mitochondrial metabolism, muscle growth and development. KEGG enrichment indicated that DEGs were involved in the amino acid metabolism. Our results indicated that replacing forage fish with formulated diets affected the muscle quality and fiber character of largemouth bass, which could provide a basis for the regulation of nutrition and accurate selection for meat traits in largemouth bass.