Multi-omics analysis of the effects of fulvic acid on the growth performance of Larimichthys crocea in summer.

In response to the mounting pressures of climate change on aquaculture, this study investigates the potential of dietary fulvic acid (FA) supplementation to improve the resilience and growth performance of large yellow croaker (Larimichthys crocea) under conditions of high temperature stress. Conducted from July 14 to September 14, the experiment involved juvenile large yellow croakers acclimatized and then distributed into five treatment groups, with FA incorporated into their diets at concentrations of 0 g/kg, 2 g/kg, 4 g/kg, 8 g/kg, and 16 g/kg. Utilizing a multi-omics approach, we analyzed the impact of FA on the transcriptomic, metabolomic, and microbiomic profiles of the fish, focusing on the liver and gut tissues. The results demonstrated substantial improvements in weight gain and specific growth rates in the FA-supplemented groups, with the highest survival and growth metrics observed at the 0.8% FA concentration. Notably, FA supplementation induced significant enhancements in metabolic pathways critical for stress response, including fatty acid degradation and the PPAR signaling pathway, which are pivotal for managing lipid and glucose metabolism under thermal stress. Additionally, FA was found to beneficially alter the gut microbiota, increasing the abundance of Actinobacteriota, which is associated with reduced inflammation and enhanced intestinal health. The study highlights the efficacy of FA in bolstering the metabolic, physiological, and immunological resilience of large yellow croaker to adverse temperature conditions, thereby providing a viable, non-antibiotic strategy to enhance aquaculture productivity in the face of global warming.