Antioxidantes na dieta de tilápia: efeitos sobre o metabolismo de peixes submetidos à hipoxia e sobre a qualidade do filé

Abstract

Chapter 1 presents the effects promoted by the inclusion of an antioxidant mixture in the diet of tilapia (Oreochromis niloticus) subjected to stress evaluation. The zootechnical performance and metabolic activity of fish under basal conditions and in stressed fish subjected to acute hypoxia (exposure to air for seven minutes) were evaluated. The experimental design was completely randomized, carried out in a water recirculation system, consisting of four treatments and five replicates, totaling twenty experimental units. The treatments consisted of a basal diet supplemented with levels of inclusion of a natural antioxidant mixture at concentrations of 0 mg/Kg; 150 mg/Kg; 500 mg/Kg and 1000 mg/Kg. The total experimental period was 80 days, divided into two sequential growth phases (first phase 35 days) and (second phase 45 days) evaluating the activity of enzymes and compounds related to oxidative stress. All treatments presented satisfactory zootechnical performance, and the 1000 mg/Kg treatment promoted higher weight gain in fish compared to the other treatments. The results demonstrate that the test ingredient promoted positive regulatory effects at certain moments of evaluation for: alanine aminotransferase; aspartate aminotransferase; glutathione; glutathione peroxidase; glutathione reductase; glutathione S-transferase; catalase; superoxide dismutase; thiobarbituric acid reactive substance; glucose; and cortisol. The results observed under the evaluated experimental conditions suggest that the evaluated antioxidants promote improvements in enzymatic activities related to combating oxidative stress. Chapter 2 addressed the effects of the antioxidant mixture on productivity (carcass yield % and fillet yield %). The evaluated parameters also included biochemical evaluation through TBARS concentration, pH values, cooking loss, and fillet exudation. The results indicated that storage time had a significant impact on product quality, with more pronounced moisture losses as a function of increased storage time. Additionally, the presence of antioxidants in the diet resulted in lower TBARS levels in chilled fillets after eight days of storage, suggesting a protective effect against lipid peroxidation.