Liver and intestine transcriptome analysis reveals molecular mechanisms of phytase-driven nutrient utilization and metabolic regulation in hybrid catfish

The use of phytase in aquafeeds has gained increasing attention as a strategy to enhance nutritional value and mitigate the adverse effects of phytic acid, especially for diets containing plant-based ingredients. Notwithstanding examples of phytase-induced phenotypic changes, the molecular mechanisms underlying phytase supplementation are not well understood. The present study evaluated the effects of phytase on the transcriptomic profiles in the liver and intestine, as well as on growth, feed conversion ratio (FCR), and hematological parameters of Jubilee × D&B hybrid catfish. Over a 140-day feeding trial, phytase supplementation (2500 phytase units/kg diet) significantly improved growth, FCR, red blood cell count, hematocrit, and total cell count in the blood compared with fish fed the basal diet. By comparing the transcriptomic profiles of phytase-supplemented and control fish, we identified a distinct gene expression profile relative to controls. This profile was characterized by differentially expressed genes (DEGs) associated with mineral metabolism (including iron), energy homeostasis, protein synthesis, carbohydrate and lipid metabolism, and immune response. The putative roles of key DEGs, including their interactions in different metabolic pathways, are discussed. The current study explains the benefits of phytase supplementation on hybrid catfish performance on the molecular level, uncovers the transcriptomic mechanisms controlling these benefits, and provides valuable information for customized functional feeds in aquaculture.