Marine macroalgae Chaetomorpha aerea as a dietary supplement: Optimizing immunity and resistance to Edwardsiella tarda in tilapia (Oreochromis mossambicus)

The intensification of aquaculture has led to a rise in fish infections, necessitating the search for alternative antibiotics. In this context, our study investigated the effects of dietary supplementation with Chaetomorpha aerea, a filamentous green algae, on the immune health and resistance to infections in tilapia (Oreochromis mossambicus). Diets containing varying concentrations of C. aerea (0, 1, 2, 5, and 10 g/kg) were prepared and administered to the fish for 30 days, followed by a challenge with Edwardsiella tarda to evaluate survival rates. The results were significant. The diet containing 5 g/kg of C. aerea (group T3) brought about substantial improvements in hematological parameters, including increases in red blood cell count (RBC), hematocrit (Hct), and hemoglobin (Hb). The T3 group exhibited a robust immune response, with higher lysozyme and ceruloplasmin activity in immunological assays. LBP gene expression was significantly elevated in the spleen and thymus of fish in the T3 group, which correlated with higher survival after bacterial challenge compared to the control group. Principal Component Analysis (PCA) and cluster analysis confirmed that the 5 g/kg concentration stood out for maximizing immunological benefits without compromising the overall health of the fish. These findings highlight the robust immune response in the T3 group, a key finding of our study. We conclude that supplementation with C. aerea represents a promising and sustainable alternative in the formulation of diets for tilapia, contributing to improved health and resistance to diseases. Future studies are recommended to explore its application in other species and development stages, in addition to evaluating other health biomarkers.