Decoding feed efficiency: Liver and intestinal transcriptomics in Larimichthys crocea fed a fishmeal-free diet

Feed efficiency (FE) is a key indicator of an animal's ability to convert feed into growth, directly impacting production costs and sustainability in aquaculture. This study aimed to explore the liver and intestinal transcriptomic profiles of Larimichthys crocea individuals with high FE (H group) and low FE (L group) under a fishmeal-free diet. Differentially expressed genes (DEGs) and associated regulatory pathways were identified to shed light on potential genetic factors influencing FE traits. Compared to the L group, 53, 24, and 112 DEGs were detected in the liver, proximal intestine, and distal intestine tissues of the H group, respectively. Notably, 24 up- and 29 down-regulated genes were found in the liver, 9 up- and 15 down-regulated genes in the proximal intestine, and 41 up- and 71 down-regulated genes in the distal intestine. GO and KEGG pathway analyses highlighted 15 key genes related to metabolism ( acsl3 、 fads2 、 acaca 、 gpam 、 cel、slc10a2 、 pemt 、 agpat3、agpat4 、 acot1 and pla2g15 ) and growth ( irs2 、 fgf10、rnf15 , and deptor ) as potential candidates for improving FE in L. crocea . Quantitative PCR confirmed the up- or down-regulation of these genes in line with RNA-seq results. This study offers valuable insights into the molecular mechanisms underlying feed efficiency in L. crocea and identifies candidate genes for molecular breeding aimed at enhancing FE.