Rainbow Trout's Transcriptional Response to Fishmeal Replacement
Genetic adaptations to challenging environments, such as new feed ingredients are major drivers of evolutionary change in feral fish populations, and these underlying mechanisms are of utmost importance to geneticists and fish breeders. In order to assess the transcriptomic response triggered by adaptation to fishmeal substitutes, 31 full-sib families of rainbow trout (Oncorhynchus mykiss) were fed with three isoenergetic and isonitrogenous feeds, containing either fishmeal (control), Arthrospira platensis meal (SP) or Hermetia illucens meal (HM). Genotype x environment interactions were determined based on individual weight gain. Using estimated breeding values (EBV) for each sire, , the three families with the highest and lowest growth performance , respectively, were chosen for RNA-sequencing analysis. Significant differences were observed in weight gain between experimental groups: fish fed with the control diet (FM) exhibited significantly higher absolute weight gain compared to both, HM (p < 0.001) and SP (p < 0.01) fed fish. Differences in gene expression patterns were observed when comparing performance levels rather than diet. The SP and HM diets led to upregulation of genes compared to those containing fishmeal in both high and low performing rainbow trout. Rainbow trout fed the SP diet showed upregulation in genes involved in immunomodulatory pathways and inflammatory response, while those fed an HM diet exhibited upregulation of genes that are enriched in neurocellular pathways. To our knowledge, this is the first study to investigate changes in the liver transcriptome of rainbow trout after FM substitution with insect meal.