Aquaculture sustainability depends on several factors, such as fish nutrition, water temperature, and the type of farmed fish . A crucial component in promoting aquaculture sustainability is the replacement of fishmeal (FM) and fish oil (FO) with alternative nutrient sources. Recently, there has been an increased focus on assessing the effects of innovative feed formulations on the fish gut microbiome. It is relatively uncommon for studies to examine the combined effects of diet and temperature on rainbow trout’s gut microbiota.
Therefore, we evaluated the impact of substituting animal-based diets with plant-based diets on the composition and metabolic profiles of gut microbiota in rainbow trout (Oncorhynchus mykiss ) raised at 14°C, 18°C, or 20°C. The contents of transient fish guts were analyzed using 16S rRNA gene and shotgun sequencing methods .
The results showed Firmicutes, Fusobacteria, Proteobacteria, Spirochaetes, and Desulfobacteria (Fig. 1) as dominant phyla for most treatments. Temperature significantly influenced microbial composition with Fusobacteria disappearing at 14°C (Fig.2). However, diets did not substantially impact bacterial diversity or composition, although plant ingredien ts led to minor increased Firmicutes and Bacillae. Fusobacteriaceae were signif icantly higher in fishguts fed fishmeal-based diet . In response to plant-based protein and 100% vegetable oil blend, genes related to fatty acid metabolism and lysine degradation were increased. At KEGG level 3, fish reared at 14°C showed a significantly increase in pathways linked to pentose and glucuronate interconversions, lysine biosynthesis, glycerolipid metabolism, and glycolysis compared to 18°C or 20°C.
Through this study, insight has been provided into the relationship between diet, temperature, and gut microbiome in rainbow trout, which will facilitate improved aquaculture practices through targeted feed formulations.