Effects of soya lecithin addition on the growth, antioxidant capacity, gonad development and nutritional quality of adult sea urchin (Strongylocentrotus intermedius)

This study was conducted to investigate the effects of soya lecithin (SL) addition on the growth, antioxidant capacity, gonad development and nutritional quality of adult sea urchin (Strongylocentrotus intermedius). Five palm oil (PO)-based feeds were formulated with graded addition of SL (0%, 1.5%, 3%, 4.5%, and 6%). Fish oil (FO)- based feed (6% fish oil + 0% SL) and fresh kelp (Saccharina japonica) were used as the control diets. Each diet was randomly assigned to ten cages of sea urchins. The feeding experiment was performed in autumn season and lasting for 30 days. The results showed that the weight gain rate and gonadosomatic index were decreased due to moderate or higher addition level (3-6%) of SL. A low dosage (1.5%) of SL resulted in the most ideal attractive color and antioxidant capacity. The promoting effects of SL on the gonad development were observed at a low dosage, and were reflected by more sperm, larger oocytes and a thicker oocyte layer. However, the promoting effects of SL on gonad development were eliminated as the addition level increased to 4.5%. Male S. intermedius fed 1.5% SL showed comparable gametogenesis (stage III) to that of males fed FO and kelp. However, female S. intermedius fed formulated feeds showed markedly slower gonad development than those fed kelp, with all individuals staying in stage I and II. The deposition of arachidonic acid (ARA, 20:4n-6) increased while eicosapentaenoic acid (EPA, 20:5n-3), docosahexaenoic acid (DHA, 22:6n-3) and n-3/n-6 polyunsaturated fatty acid (PUFA) decreased as the SL addition increased. Although FO resulted in the highest growth rate and LC-PUFA deposition, it negatively affected the antioxidant capacity. In conclusion, the optimal SL requirement was recommended to be no more than 1.5% in the PO-based diets for adult S. intermedius from the perspective of growth, antioxidant capacity, gonad development and nutritional quality. PO based diets showed comparable effects to FO based diets on the growth performance and gonad development. These results can contribute to optimization of the feed formulation for producing S. intermedius gonads that are high in quantity and quality.