Antioxidant, metabolic and digestive biomarker responses of farmed Sparus aurata supplemented with Laminaria digitata

Abstract

The present study aimed to investigate the effectiveness of supplemented diets with the brown macroalga Laminaria digitata in improving the antioxidant, metabolic and digestive performance in gilthead seabream (Sparus aurata), using a multi-biomarker approach. Three experimental diets supplemented with 1.5 %, 3 % and 6 % of dried powdered L. digitata were tested against a control diet. After 30 and 60 days, S. aurata juveniles were sampled and muscle, gut and liver tissues were collected. Results showed that fish fed with 1.5 % L. digitata exhibited higher specific growth rate (SGR) after 30 days. Additionally, at this supplementation level, there was a significant reduction in antioxidant enzyme activities (catalase, CAT; glutathione S-transferase, GST; superoxide dismutase, SOD) and in lipid peroxidation (LPO) in muscle and liver tissues. In contrast, gut antioxidant enzyme activity increased with higher macroalga concentrations (3 % and 6 %). Fish fed with 6 % L. digitata revealed a significant decrease in muscle aerobic potential (citrate synthase (CS) activity) but increased anaerobic capacity (lactate dehydrogenase (LDH) activity). Moreover, the 1.5 % L. digitata supplemented diets led to a significant increase in amylase activity after 30 days. After 60 days, fed with 6 % L. digitata showed lower hepatosomatic index (HSI) compared to animals fed on control diet. Additionally, trypsin activity was higher in fish fed the supplemented diets, especially at 3 % L. digitata. Pepsin activity was significantly supressed in fish fed diets with higher macroalga concentrations (3 % and 6 %). Overall, the current findings highlight the beneficial effects with lower doses of L. digitata on farmed marine fish performance and welfare. However, additional research is needed to establish the most cost-effective seaweed supplementation dose and validate this strategy at an industrial scale.