Immunomodulation, antioxidant enhancement and immune genes up-regulation in rainbow trout (Oncorhynchus mykiss) fed on seaweeds included diets

This study investigated the stimulatory effects of dietary inclusion of Gracilariopsis persica (GP), Hypnea flagelliformis (HF) and Sargassum boveanum (SB) on immune indices, antioxidant capability and immune related genes expression of rainbow trout (Oncorhynchus mykiss). Seven iso-nitrogenous and iso-caloric diets with 0, 5 and 10% of each macroalgae were prepared and fed to rainbow trout juveniles for 83 days. Serum lysozyme (Lyz) and respiratory burst activity (NBT) along with activity of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) and expression of LyzII, TNF alpha and IL-1 beta genes in head kidney samples were determined by days 47 and 83. Our results revealed that dietary inclusion of seaweeds improved fish immune status. Long term feeding of fish on seaweed contained diets (except for GP10) improved serum Lyz activity in comparison to control group. Similarly, extended feeding on GP5 and HF10 and HF10 included diets improved SOD and POD levels, respectively. Genes expression studies revealed that seaweeds contained diets noticeably enhanced expression of LyzII, TNF alpha and IL-1 beta in comparison to control fish. However, results revealed that such stimulatory effects were more evident at lower dietary inclusion level and shorter feeding time. In conclusion, the results depicted that dietary inclusion of the seaweeds effectively improved serum immune indices and head kidney antioxidant status and immune related genes expression in a time and dose dependent manner.