Dietary Schizochytrium sp. Meal Enhances the Fatty Acid Profile in Pirarucu (Arapaima gigas) Fillets with No Effect on Growth Performance and Health Status

This study aimed to assess the impact of dietary supplementation with <i>Schizochytrium</i> sp. meal, a source of docosahexaenoic acid (DHA), on the growth, hemato-biochemical parameters, and fatty acid composition of juvenile pirarucu (<i>Arapaima gigas</i>). Two diets were used: a test diet (5%SZ) and a control diet (0 SZ). Juvenile pirarucu (561.3 ± 13.4 g; 47.5 ± 7.1 cm) were kept in recirculating aquaculture tanks and fed three times daily for 12 weeks. No significant differences in growth performance or adverse effects on hemato-biochemical parameters were found, except for hemoglobin and total protein. The fatty acid profile of the fillets from the fish fed the 5 SZ diet mirrored that of the <i>Schizochytrium</i> sp. meal, with increased levels of palmitic acid, DHA, and eicosapentaenoic acid (EPA), and decreased levels of linoleic and linolenic acids. The inclusion of <i>Schizochytrium</i> sp. meal reduced monounsaturated fatty acids from 39.6% to 32.0% and increased highly unsaturated fatty acids from 3.05% to 11.9% of total lipids. The DHA content was 9.45 times higher in the fillets of the fish fed 5 SZ, improving the n-3/n-6 ratio from 0.26 to 1.19. In conclusion, adding 5% <i>Schizochytrium</i> sp. meal enhances the nutritional quality of pirarucu fillets by increasing DHA and the n-3/n-6 ratio.