Effect of dietary seaweed (Gracilaria pulvinata and Sargassum ilicifolium) on growth, immune and antioxidant responses, and muscle fatty acid composition of Sobaity seabream (Sparidentex hasta)

The aim of this study was to evaluate the impacts of dietary Gracilaria spp. and Sargassum spp. on growth, immunity, antioxidant status, and fatty acid composition of Sobaity seabream (Sparidentex hasta). A total of 540 Sobaity seabream juveniles (19.6 ± 0.5 g) were stocked into 18 tanks (300 L) and divided into six groups (three replicates per group). Fish were fed diets containing 0 (control), 3% (GS3), 6% (GS6), 9% (GS9), 12% (GS12), and 15% (GS15) Gracilaria and Sargassum mixtures in equal amounts for 8 weeks. The results showed that final weight, weight gain rate, and specific growth rate were significantly higher in fish fed GS6, GS9, and GS12 groups. Serum lysozyme, ACH50 activities, complement 4 (C4), and total Ig values were significantly increased in fish fed the 6% and 12% macroalgae mixture. The lowest liver catalase activity was found in the control, while liver superoxide dismutase (SOD) activity in the GS9 and GS12 groups was significantly higher than in the GS3 group. The highest and the lowest values of liver glutathione were observed in the GS12 and GS15 groups, respectively. Liver total antioxidant capacity content was also the highest in the GS12 group. Insulin-like growth factor-1 (IGF-1) relative expression level, in the liver of fish, was increased in the GS6-GS12 groups. Lysozyme relative expression level was significantly higher in the liver of fish fed macroalgae. Arachidonic acid (ARA) and eicosapentaenoic acid (EPA) were significantly higher in the GS9, GS12, and GS15 groups than in the control. Moreover, there were no significant differences in the amounts of docosahexaenoic acid (DHA), n-3 and n-6 polyunsaturated fatty acids (PUFA), long-chain PUFA, and n-3/n-6 PUFA among the experimental groups. Therefore, adding 9–12% Gracilaria and Sargassum macroalgae mixture in equal amounts to fish diets can be recommended to improve growth performance, innate immunity, liver antioxidant status, and muscle fatty acid composition in Sobaity seabream.