Antioxidant capacity of meagre (Argyrossomus regius) fed different lipid content and source, with and without selenium

• ¹ CIIMAR - Interdisciplinary Centre of Marine and Environmental Research, Portugal
• ² UFPB - Universidade Federal da Paraíba, CAPES PhD Schollarship - Process nº 0277-13-4., Brazil
• ³ University of Aveiro, CESAM e Department of Biology, Portugal
• ⁴ ICBAS - Abel Salazar Biomedical Sciences Institute, University of Porto, Portugal
• ⁵ Instituto de Pesca, Brazil

Selenium, an essential micromineral, is a co-factor of the antioxidant enzyme glutathione peroxidase. This enzyme is involved in cell membrane protection against oxidative damage resulting from reactive oxygen species production. Besides the importance of preservation of unsaturated fatty acids in fish, world aquaculture has been seeking for alternative oil sources in diet of fish. Thus, the main goal of this research work was to study the antioxidant capacity of meagre (Argyrossomus regius) fed with different levels of vegetable blend oil with and without selenium in replacement of traditional diets containing fish oil.

Meagre (600 animals) were kept in 24 tanks (80 L) with constant renovation and aeration and maintained at 20.7 ± 0.7ºC and oxygen 8.8 ± 1.7 mg L^-1. Fish were fed twice per day, six days per week, with eight different experimental diets for 60 days. Diets were formulated to have two different oil sources (fish or vegetable blend oils with 45% of linseed, 35% of rapeseed and 20% of soybean oil), two lipid levels (12 and 17%) and two selenium supplementation (0 and 1 mg/kg diet). Lipid peroxidation (LPO), glutathione reductase (GR), glutathione peroxidase (GPx), total glutathione (TG) and catalase (CAT) were analyzed in liver of fish.

CAT, GPx and GR activities were not significantly altered in fish fed with diets with different oil sources. However, TG in fish fed with fish oil diet was higher than the levels observed in fish fed with vegetable blend oil. Furthermore, fish fed with fish oil diet showed lower lipid peroxidation when compared with fish fed vegetable blend oil diet (Table 1). Concerning the oil level in diet, it was observed that fish fed with a diet of 17% lipids had a higher level of total glutathione when compared to fish fed with a diet of 12% lipids. On the other hand, the fish fed with a diet with 12% lipids showed lower levels of lipid peroxidation when compared to fish fed with a diet of 17% lipids. Fish fed with diets supplemented with selenium showed a significantly increased activity of GPx when compared with fish fed without selenium. Three-way ANOVA analysis showed that dietary lipid level and the presence of selenium have a significant interaction on the activities of CAT and GR, as well as, levels of TG and LPO. A significant interaction between the source of oil and the presence of selenium on GR activities was observed. Interaction on source and level was observed to CAT. In conclusion, the antioxidant capacity of meagre is influenced by the source of oil, the level of lipids and the presence of selenium in their diet.