Deciphering the Effects of Plant Oil Diets in Channa striata (BLOCH, 1793) using an Integrated Transcriptomic and Metagenomic Approach.

This study evaluated the effects of substituting dietary fish oil with plant-based oils on the growth performance, fatty acid profiles, antioxidant capacity, hepatic histology, transcriptome expression, and gut microbiota of Channa striata over an 8-week feeding trial. Juvenile fish was assigned to five dietary treatments: fish oil (control), soybean oil (T1), linseed oil (T2), mustard oil (T3), and a 1:1:1 blend of soybean, linseed, and mustard oils (T4). Among the treatments, mustard oil (T3) showed the most balanced physiological response, antioxidant enzyme activities, and maintaining hepatic integrity. Transcriptomic analysis revealed significant up-regulation of key lipid metabolism genes ( Fads , Elovl5 , SREBP1c , ACACA , ELOVL6 ) in T3, indicating active polyunsaturated fatty acid (PUFA) biosynthesis. Antioxidant enzymes, including superoxide dismutase and catalase, were significantly elevated in T2 and T3, which also showed better hepatic histology, indicating enhanced oxidative defence mechanisms. Gut microbial profiling shows diet-driven community shifts, with enrichment of beneficial taxa such as Bifidobacterium longum , and Faecalibacterium prausnitzii in T3-fed fish, accompanied by functional predictions of indicated enhanced fatty acid biosynthesis and ribosome biogenesis, with reduced virulence-associated pathways. Canonical correspondence analysis linked fatty acid composition to microbial community variation. Altogether, mustard oil effectively supported growth via improved lipid metabolism, hepatic function, antioxidant defence, and a beneficial gut microbiome composition, highlighting it may potential as a sustainable and health-promoting alternative to fish oil in aquafeeds. • Dietary plant oils improved growth and shaped fatty acid metabolism. • Mustard oil promoted liver health and boosted fatty acid synthesis genes. • Gut microbial composition shifted with the replacement of plant oils. • Beneficial microbes supported fatty acid pathways and antioxidant defence. • Findings show diet and microbes enhance sustainable fish aquaculture