Beta-Glucans and Mannan Oligosaccharides Enhance Growth and Immunity in Nile Tilapia

We studied the effects of a combination of dietary beta-glucans (beta-G) and mannan oligosaccharides (MOS) on Nile Tilapia Oreochromis niloticus. Three-hundred-sixty fingerlings (mean mass +/- SD = 8.7 +/- 0.4 g) were separated into three groups (G(1), G(2), and G(3)) of 120 fish; G(1) (control group) was fed a basal diet, whereas G(2) and G(3) were fed prebiotic-supplemented diets at final levels of 1.5 and 3.0 g/kg feed, respectively. Each group was subdivided into two subgroups: subgroup A was fed for 60 d to evaluate growth performance, nutrient utilization, intestinal morphometry, and body composition; and subgroup B was fed for 30 d to evaluate immune status and disease resistance. The best growth and feed utilization were observed in G(3). There was no significant difference in final body weight or weight gain between G(2) and G(1) after 30 d, whereas both variables were significantly higher in G(2) than in G(1) after 60 d. At the end of the feeding period, G(2) had a better feed conversion ratio than G(1). Villus height, number of goblet cells, and number of intraepithelial lymphocytes were greatest in G(3), followed by G(2) and then G(1). Whole-body protein content and fat content were higher in G(3) than in G(2) and G(1). Only G(3) had significantly higher serum total protein, albumin, and globulin than G(1). Serum killing percentage and phagocytic activity were significantly higher in G(3) than in G(1) and G(2), whereas serum lysozyme activity was significantly higher in G(3) and G(2) than in G(1.) The nitric oxide assay indicated a significant effect in G(3) compared with G(1) after 30 d. Fish that were fed the prebiotic mixture had better relative percent survival than G(1) fish after challenge with Yersinia ruckeri. Dietary supplementation with beta-G and MOS in combination improves the performance of Nile Tilapia.