Effect of replacement of fish oil with different plant oils in Oncorhynchus mykiss broodstocks diets on egg and larval antioxidant defense development

This study was undertaken to investigate the effects of feeding rainbow trout (Oncorhynchus mykiss) broodstocks with different ratio of plant oils to evaluate the changes in antioxidant defense status in the progenies. In the experimental diets, fish oil was replaced with different combination of plant oils including corn oil, olive oil, sunflower oil, and coconut oil, to gain different levels of polyunsaturated fatty acids (PUFA) and highly unsaturated fatty acids (HUFA) in the experimental diets. Fish fed eight weeks with experimental diets before reproduction. After spawning, samples were taken on days 0, 5, 10, 15, 20, 25, 30 and 35 after fertilization. The samples were homogenized, centrifuged and the supernatant was removed for determination of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) activity and malondialdehyde (MDA) content. Results showed that SOD activity was significantly increased from the first sampling to day 35 in all treatment groups. The CAT activity showed a downward trend, as the highest CAT activity was observed in the eggs immediately after fertilization. The GPX activity declined until day five and then showed an increasing trend. The MDA content did not show significant changes in different groups and at different sampling times. The antioxidant enzymes activity was significantly influenced by the dietary PUFA level in the experimental groups but no change in MDA content was recorded, suggesting that the different percentages of fish oil replacement used in this study could not result in oxidative stress in early life stages of O. mykiss.