Effect of dietary -glucan supplementation on growth performance, body composition, intestinal microbes, and capacity against pathogen of golden trevally (Gnathanodon speciosus, family Carangidae)

The efficacy of dietary beta-glucan supplementation in golden trevally (Gnathanodon speciosus) was evaluated. The fish were fed five different diets supplemented with 0%, 0.05%, 0.10%, 0.20%, and 0.40% beta-glucan for 56 days. After 56 days of culture, survival was the highest when the fish were fed a 0.10% beta-glucan diet. Growth rates were higher in fish fed diets supplemented with all beta-glucan levels. Lymphocytes increased when the fish were fed a diet supplemented with 0.05% beta-glucan, and thrombocytes increased when the fish were fed 0.2% and 0.4% beta-glucan-supplemented diets. The total aerobic bacteria count in the gut of golden trevally was higher (p < 0.05) and the total Vibrio counts in the gut of golden trevally were lower (p < 0.05) when the fish were fed any level of beta-glucan. Flesh protein content was higher and flesh lipid content was lower when fish were fed beta-glucan-supplemented diets at levels greater than 0.1%. When challenged with Streptococcus iniae, fish fed diets containing 0.10% or 0.20% beta-glucan exhibited the highest survival rates. The current results suggest that supplementation with 0.05 to 0.2% beta-glucan in the diet would be beneficial for the culture of the golden trevally.