Nutriphysiological and cytological responses of juvenile channel catfish (Ictalurus punctatus) to dietary oxidized fish oil

An 86-day growth trial was conducted to investigate the effect of dietary oxidized fish oil on the growth and cytopathology of juvenile channel catfish (Ictalurus punctatus). Four diets containing 0 g kg ^-1 (control: fresh fish oil), 30 g kg ^-1 (low-oxidized oil group), 60 g kg ^-1 (medium-oxidized oil group) and 90 g kg ^-1 (high-oxidized oil group) graded oxidized oil levels with the same dietary lipid level (90 g kg ^-1 diet) were evaluated. The results show that the specific growth rate decreased with increasing dietary oxidized oil level (P < 0.05). All examined liver and kidney tissues in all dose groups exhibited what appeared as dose-dependent cellular modifications. In addition, lipid droplet accumulation in the hepatocytes of fish in all dose groups was increased, and their localizations were distinctly different between all dose groups. The ultrastructural changes suggest the progression of mitochondrial vacuolation, especially in the renal tubules, in all dose groups. These results reveal a previously underappreciated effect of dietary oxidized fish oil on channel catfish kidneys. Overall, a series of nutriphysiological responses were adversely affected by exposure to dietary oxidized fish oil, and the corresponding interference patterns on the metabolism and transport of nutrients within cells were observed.