Growth, oxidative stress, and intermediary metabolism of European seabass (Dicentrarchus labrax) juveniles fed diets including solid-state fermented distiller's dried grains with solubles

Previous research demonstrated that solid-state fermentation (SSF) of distiller's dried grains with solubles (DDGS) by Aspergillus ibericus improved protein, reduced neutral and acid detergent fiber levels, and added phenolic compounds, xylanase, and cellulase. Fermentation of DDGS also increased protein, lipids, energy, and starch digestibility. This study evaluated the effects of unfermented and fermented DDGS on growth, oxidative stress, and intermediary metabolism of European seabass ( Dicentrarchus labrax ) juveniles. Five different diets were prepared: a control diet without DDGS and four with 10 % or 20 % unfermented or fermented DDGS (diets 10DDGS, 20DDGS, 10SSF-DDGS, and 20SSF-DDGS). Each diet was fed to triplicate seabass (30 ± 5 g) for 12 weeks. The 10SSF-DDGS diet increased the protein efficiency ratio, final body weight, and nitrogen retention (% N intake) compared to the 10DDGS diet, with no differences from the control diet. Both 20 % DDGS diets reduced growth performance, but the 20SSF-DDGS diet showed higher feed and protein utilization than the 20DDGS diet. Whole-body composition was unaffected except for 20SSF-DDGS, which had lower dry matter, lipids, protein, and gross energy content. The 10SSF-DDGS diet reduced hepatic glucose-6-phosphate dehydrogenase activity, while the 20SSF-DDGS diet decreased amino acid catabolism enzyme activity and increased glucokinase and pyruvate kinase activity. In intestinal oxidative status, 10DDGS reduced superoxide dismutase and increased glutathione reductase, glutathione peroxidase, and lipid peroxidation, whereas the 10SSF-DDGS diet mirrored the control diet. In conclusion, SSF of DDGS enhances feed utilization and maintains intestinal oxidative status, particularly at lower inclusion levels, highlighting its potential as an improved alternative to unfermented DDGS in aquafeeds. However, further research involving long-term trials, thermal stress challenges in the context of climate change, and disease resistance assessments is necessary to confirm its broader applicability in aquaculture.