Antioxidant potential of lipoic acid in the diet of Litopenaeus vannamei shrimp
Abiotic factors are one of the main problems in aquaculture, as their alteration can result in low growth level or induce harmful effects that can eventually lead to the death of organisms. In this work, a simulation of the dissolved oxygen variation was performed with the aeration shutdown until the levels in the tanks reached 3 mg/L (hypoxia condition) when the aeration was then restarted. Based on these conditions, the increase in the antioxidant competence of the shrimp Litopenaeus vannamei (Boone, 1931) was evaluated as a result of the action of lipoic acid (LA) applied to the feed, in the doses of 35, 70 and 140 mg of LA for each 1 kg of when exposed to a situation of hypoxia/re-oxygenation. Male and female shrimp with an initial weight of 2.07 g (+ 0.24) were used.The activity of the enzyme glutathione-S-transferase (GST) increased at a dose of 70 mg of LA/kg in the gills, however, in the hepatopancreas the response was biphasic, sometimes increasing and sometimes decreasing. Analyzes of lipid peroxidation levels (TBARS) in gills found that LA induced a strong antioxidant effect at a dose of 70 mg/kg after 4 h of re-oxygenation. In the hepatopancreas, LA reduced TBARS levels after 0.5 h of reoxygenation at a dose of 35 mg LA/kg, and immediately after 4 h it had a pro-oxidant effect. In the evaluation of the total antioxidant capacity against peroxy-radicals it was found that in normoxia the doses of 70 and 140 mg LA/kg induced an antioxidant effect on the gills of the shrimp. In hepatopancreas, in normoxia, the dose of 70 mg LA/kg promoted an antioxidant effect,while in organisms submitted to hypoxia/re-oxygenation it was found that the dose of 140 mg LA/kg promoted an increase in antioxidant capacity. Also, in the two highest doses of LA (70 and 140 mg/kg) an increase in weight of the shrimp was observed. It is suggested that the most suitable dose is 70 mg of LA for 1 kg of feed, as it presents better results in biochemical analyzes and for inducing weight gain in shrimp, which reached a final weight of 7.94 g (+ 0.15).