Dietary sodium alginate administration to enhance the non-specific immune responses, and disease resistance of the juvenile grouper Epinephelus fuscoguttatus

Survival rates of the juvenile grouper Epinephelus fuscoguttatus against Streptococcus sp. and an iridovirus, and non-specific immune parameters such as alternative complement activity (ACH50), lysozyme activity, natural hemagglutination activity, respiratory bursts, superoxide dismutase (SOD) activity, and phagocytic activity were determined when the fish were fed diets containing sodium alginate at 1.0, or 2.0 g kg− 1. Fish fed a diet containing sodium alginate at the level of 1.0 or 2.0 g kg− 1 had a significantly higher survival rate than those fed the control diet after challenge with Streptococcus sp. and an iridovirus. The ACH50 level, lysozyme activity, respiratory bursts, phagocytic activity, and SOD level of fish fed diets containing sodium alginate at 1.0 and 2.0 g kg− 1 after 6–9 days significantly increased, compared to those of fish fed the control diet. We therefore recommend dietary sodium alginate administration at ≥ 1.0 g kg− 1 to enhance immunity and resistance against Streptococcus sp. and an iridovirus of E. fuscoguttatus.