Growth performance and gene expression in gilthead sea bream (Sparus aurata) fed microdiets with high docosahexaenoic acid and antioxidant levels

This study aimed to determine the effects of increasing docosahexaenoic acid (DHA) levels in Sparus aurata diets supplemented with antioxidants vitamins (vitamins C and E). Six isoproteic and isolipidic formulated diets, which varied in the DHA content (38–78 g kg−1 TFA), were fed to 19 dph S. aurata larvae. No significant differences were found in survival rates or growth, which indicates that all the diets covered the minimum essential fatty acid requirements of this species. Stress resistance was not negatively affected by dietary DHA contents. In agreement, two biomarkers of the oxidative stress of the fish and the gene expression of superoxide dismutase and glutathione peroxidase were not affected by the elevation of dietary DHA, denoting that fish were sufficiently protected from oxidative damage even at high dietary DHA contents. The elevation of dietary DHA did affect neither the occurrence of skeletal malformations nor the expression of osteological markers such as run-related transcription factor 2 or alkaline phosphatase. The results of this study have confirmed that increase of the dietary DHA levels in gilthead sea bream diets does not negatively affect larval performance if the larvae are protected from peroxidation risks. Despite not being harmful, increase of DHA over the recommended requirements does not have any significant improvement in larval performance.