Growth-promoting effects and molecular mechanisms of long-term fasting in red sea bream (Pagrus major)

Improving productivity in red sea bream ( Pagrus major ) aquaculture remains a key challenge, with optimized feeding strategies playing a critical role in reducing costs and promoting environmental sustainability. This study examined the effects of a three-week fasting period followed by resumed feeding on growth performance and metabolism in a commercial aquaculture setting. After feeding resumed, the previously fasted group exhibited accelerated growth and achieved final body weights equal to or greater than those of the control group ( p = 0.035). Additionally, an improved feed conversion ratio was observed, suggesting that fasting may enhance feed efficiency. To elucidate the molecular mechanisms underlying compensatory growth, gene expression in liver and muscle tissues was analyzed. Gene Ontology analysis revealed significant enrichment of the insulin-like growth factor (IGF) receptor signaling pathway in the liver of fish subjected to fasting, indicating that elevated IGF signaling may have contributed to post-fasting growth acceleration. These findings suggest that strategic long-term fasting could be an effective feeding management approach to enhance growth performance and feed efficiency, thereby improving aquaculture productivity. • A fasting trial in farmed red sea bream induced compensatory growth, resulting in final body weights comparable to controls. • Molecular evidence indicates that rapid growth after fasting in sea bream results from physiological changes upon refeeding. • The fasting treatment reduced feed costs and, when combined with improved FCR, markedly reduced overall aquaculture expenses.