Effect of dietary oil source on mitigating oxidative stress in tambaqui (Colossoma macropomum) juveniles subjected to acute cold stress

Abstract This study assessed the effect of dietary oil sources on tambaqui ( Colossoma macropomum ) exposed to acute cold stress. Three different oil sources were incorporated individually at 7% into the diets: fish oil (FO), a blend of linseed and palm oils (LO), or corn oil (CO). These diets differed in their n-6/n-3 polyunsaturated fatty acid (PUFA) ratios, with n-3 PUFA derived from EPA + DHA (FO) or linolenic acid (LO) and n-6 PUFA from linoleic acid (CO). Fish (initial weight, 43 g) were fed ad libitum at 28°C for 49 days before the water temperature was reduced to 21°C within 40 min. Sampling occurred before (0h) and at 3h and 24h after cold stress. The dietary oil source had no significant effect on growth performance. Plasma cortisol and glucose levels were lowest at 3h post-stress, with FO-fed fish showing consistently reduced cortisol levels regardless of time. Plasma glucose was unaffected by diet composition. At 0h, fish fed the LO diet showed the lowest hepatic lipid peroxidation (LPO) levels, while at 3h and 24h, fish fed the FO and CO diets and the FO and LO diets showed lower LPO levels, respectively. Enzymatic activities of SOD, GPX, and GR exhibited a decline at 3 h and 24 h relative to the initial time point (0 h) across all dietary treatments. LPO levels also decreased post-stress, except in CO-fed fish at 24h. In conclusion, dietary n-3 PUFA improves oxidative stress resilience in tambaqui during acute cold exposure.