Hepatic oxidative stress in Atlantic salmon (Salmo salar L.) transferred from a diet based on marine feed ingredients to a diet based on plant ingredients

The aim of the present study was to examine whether a combined plant protein and vegetable oil replacement (P diet) of fish-based marine feed ingredients (F diet) imposes oxidative stress on Atlantic salmon after short- and long-term feeding. Oxidative stress was assessed by measuring a suit of hepatic biomarkers, including TBARS, enzymatic and transcriptional levels of a set of antioxidant proteins as well as antioxidant vitamins. Antioxidants assessed regularly in the long-term study were influenced by the dietary compositions, mostly influencing liver astaxanthin and tocopherols. In the short-term crossover study, fish were sampled initially, at Day 2 and at Day 17 after transfer to new diet. The results showed that fish relocated from the F diet to the P diet had significantly lower transcriptional levels of CuZn SOD (Day 2, P < 0.006) and Mn SOD (Day 17, P < 0.003), in addition to lower levels of catalase protein (Day 17, P < 0.05) and total glutathione (Day 17, P < 0.05). At Day 17, both groups of fish relocated to new diets had significantly increased transcriptional levels of GSH-Px (F-P: P < 0.05, P-F: P < 0.007). This study showed that switching from a marine-based to a plant-based diet affected Atlantic salmon gene expression and the antioxidative defence in the fish.