Effects of Dietary β-glucan Supplementation on Growth, Innate Immune, and Capacity Against Pathogen Streptococcus iniae of Juvenile Pompano (Trachinotus ovatus)

This study investigated the effect of dietary β-glucan on growth, immunity, and resistance against Streptococci in pompano T. ovatus. Pompano were fed a control diet, and diets which included 0.10% or 0.20% of β-glucan. After being fed the diets for 3-weeks, growth rate, survival, blood parameters, and immunity were examined, and the fish were challenged with Steptococcus aniae for 10 days. At the end of the feeding trial, RBC, WBC, WBC:RBC ratio, and lymphocytes significantly increased (P ≤ 0.032), while monocytes significantly decreased (P ≤ 0.007) in fish fed 0.10-0.20% of β-glucan. Moreover, lysozyme was significantly higher (P ≤ 0.003) in fish fed β-glucan, while the phagocytic ratio was only significantly higher (P = 0.037) in fish fed 0.10% β-glucan. Furthermore, fish fed 0.10-0.20% β-glucan showed higher protection against S. iniae (P ≤ 0.002). Thus, a diet of β-glucan is recommended to improve non-specific immunity, growth in T. ovatus, and also to limit the adverse effects of S. aniae disease in this species