Dietary β-glucan improved growth performance, Vibrio counts, haematological parameters and stress resistance of pompano fish, Trachinotus ovatus Linnaeus, 1758

This study evaluated effects of graded levels of dietary beta-glucan (0, 0.5, 1, 2 and 4 g kg(-1)) on growth performance, haematological parameters, intestinal Vibrio counts, dose requirement and salinity stress resistance in pompano fish Trachinotus ovatus (6.45 g +/- 0.06 (SEM)). After 8-weeks of diet feeding, growth was significantly higher in fish fed diets with 0.10% beta-glucan compared to fish fed control diet (no P-glucan). Survival increased significantly in fish fed 0.05 and 0.10% beta-glucan compared to control diet. There were significant increases in red blood cells (in 0.20% (beta-glucan diet), in total leukocytes (in 0.05 -0.20% beta-glucan diet), in both lymphocyte and monocyte count in fish fed 0.10%-0.40% beta-glucan diet. However, dietary beta-glucan did not affect neutrophil, eosinophil and basophil counts. Intestinal Vibrio counts were reduced in fish fed any level of beta-glucan compared to control. In addition, dietary beta-glucan levels highly correlated with growth, survival, intestinal Vibrio counts and haematological index. Optimal beta-glucan levels for maximal growth of fish were predicted to be 0.122% at day 21 (R-2 = 98.53%), 0.120% at day 28 (R-2 = 78.55%), 0.115% at day 42 (R-2 = 62.21%) and 0.090% at day 56 (R-2 = 75.18%), showing a decreasing beta-glucan requirement with increasing fish size. Furthermore, optimal beta-glucan levels for maximal haematological parameters based on lymphocyte count, was estimated to be 0.120% (R-2 = 98.53%) at day 56. Also, fish fed 0.05%-0.20% beta-glucan showed better resistance against salinity stress. In conclusion, beta-glucan supplementation is effective for improving growth, intestinal Vibrio counts and boosted stress resistance of the pompano fish, T. ovatus. (C) 2016 Elsevier Ltd. All rights reserved.