Dietary fish oil-corn oil balance modulates growth and metabolic homeostasis of Acrossocheilus fasciatus (Steindachner, 1892) under chronic heat stress.

Heat stress is a growing constraint in aquaculture, yet effective nutritional strategies for newly domesticated stream-dwelling fish remain poorly understood. Here, we investigated whether dietary lipid-source supplementation of a commercial feed could modulate chronic heat stress responses in the stream-dwelling fish Acrossocheilus fasciatus. Fish were reared for 60 days under two temperature regimes (24 °C and 32 °C) and fed a commercial basal diet supplemented with graded fish oil (F) to corn oil (C) ratios: F0:C4, F1:C3, F2:C2, and F4:C0. Growth performance, survival, brain cortisol, liver histology, and hepatic expression of genes involved in lipid remodeling, inflammation, and glycolytic metabolism were evaluated. High temperature significantly depressed growth and increased cortisol concentration, hepatic vacuolization, and the expression of stress-responsive metabolic and inflammatory genes. These adverse effects were most evident in the F0:C4 group, which showed the lowest growth, the highest cortisol level, strong induction of fads2, elovl5, tnfα, il6, eno1, and aldoa, and pronounced liver damage under 32 °C. Moderate fish oil supplementation, particularly the F1:C3 diet, alleviated several heat-induced alterations, preserving liver integrity and reducing inflammatory and glycolytic responses. By contrast, the F4:C0 diet improved growth at 24 °C but did not provide comparable protection against hepatic and inflammatory disturbances under 32 °C. These results indicate that dietary lipid source can modulate heat stress responses in A. fasciatus and that diets supporting growth under optimal temperature may not necessarily provide the most favorable physiological response under warming conditions. Overall, a moderate fish oil-to-corn oil ratio showed the most balanced physiological response under chronic heat stress.