Effect of dietary Spirulina (Arthrospira platensis) on the growth performance, immune-related gene expression and resistance to Vibrio anguillarum in European seabass (Dicentrarchus labrax)

This research was conducted to reveal the effects of dietary Spirulina (Arthrospira platensis) meal on the growth performance, immune responses and resistance against Vibrio anguillarum in European seabass (Dicentrarchus labrax). In the study, the fish (5.74 +/- 0.02 g) were fed with control (C) and three different levels (1%, 2.5% and 5%) of Spirulina meal-containing diets (SP1, SP2.5 and SP5) for 60 days. The adaptive and innate immune responses of fish were determined every 30th day of the study. The results showed that respiratory burst activity (RBA) was significantly elevated on the SP2.5 and SP5 groups on the 30th day of the study. Lysozyme activity (LYS) was increased on the SP1 group on the 30th day and the SP5 group on the 60th day (p < 0.05). Myeloperoxidase activity (MPO) was raised on the 60th day of the SP2.5 and SP5 groups compared with the C (p < 0.05). IL-1 beta gene expression increased in the kidney and intestine of fish on the 30th day and in the spleen on the 60th day. IL-10 gene expression in the intestine of fish fed the Spirulina-containing diet was elevated at each sampling time relative to the C group (p < 0.05). Elevated IL-6 activity was determined in the kidney and the intestine on all Spirulina-fed groups compared with control at both sampling times. Similar to IL-6, IL-8 gene expressions were elevated in all Spirulina-fed groups (p < 0.05). TNF-alpha was up-regulated in the kidney and intestine of all Spirulina-fed groups compared with the C group on the 30th day of the study (p < 0.05). TGF-beta gene expression was increased in the kidney and intestine of all Spirulina groups compared with the C group on all sampling times. COX-2 gene expression in the kidneys and intestines of fish fed with Spirulina diets was significantly elevated compared with the C diet at days 60th and 30th respectively. Hepcidin gene expression of all groups was elevated in all tissue samples on the 30th day of the study. The survival rate of fish infected with V. anguillarum was higher in all Spirulina-fed groups than in the C group. The feed conversion rate and protein efficiency ratio of fish fed with a 1% Spirulina diet was found to be better than those fed with other diets. These results show that up to the 5% inclusion of Spirulina meal in European seabass diets promotes some growth parameters and supports immunity in fish.