Effects of dietary mannan oligosaccharide on growth performance, gut morphology and stress tolerance of juvenile Pacific white shrimp, Litopenaeus vannamei

An 8-week feeding trial was conducted to investigate the effects of dietary mannan oligosaccharide (MOS) on growth performance, gut morphology, and NH3 stress tolerance of Pacific white shrimp Litopenaeus vannamei. juvenile Pacific white shrimp (1080 individuals with initial weight of 2.52 +/- 0.01 g) were fed either control diet without MOS or one of five dietary MOS (1.0, 2.0, 4.0, 6.0 and 8.0 g kg(-1)) diets. After the 8-week feeding trial, growth parameters, immune parameters, intestinal microvilli length and resistance against NH3 stress were assessed. Weight gain (WG) and specific growth rate (SGR) were significantly higher (P < 0.05) in shrimp fed 2.0, 4.0, 6.0 and 8.0 g kg(-1) MOS-supplemented diets than shrimp fed control diet WG and SGR of shrimp fed 2.0 g kg(-1) MOS-supplemented diet was the highest (P < 0.05) in all experimental groups. Survival rate (SR) of shrimp was generally similar (P > 0.05) in all experimental groups. Compared with control group, TEM analysis revealed that 2.0, 4.0, 6.0 and 8.0 g kg(-1) MOS supplementation could significantly increase (P < 0.05) the intestinal microvilli length of shrimp at the ultrastructural level. After NH3 stress for 24 h, SR of shrimp fed 2.0, 4.0, 6.0 and 8.0 g kg(-1) MOS-supplemented diets was significantly higher (P < 0.05) than that of shrimp fed control diet. Phenoloxidase (PO) activity of 4.0 g kg(-1) MOS-supplemented group was significantly higher (P < 0.05) than that of control group under normal conditions and NH3 stress. PO activity significantly decreased (P < 0.05) under NH3 stress than under normal conditions. Superoxide dismutase (SOD) activity of 4.0, 6.0 and 8.0 g kg(-1) MOS-supplemented groups was significantly higher (P < 0.05) than that of control group under normal conditions. After NH3 stress for 24 h, SOD activity of all experimental groups also significantly decreased (P < 0.05) compared to normal conditions. These results clearly indicated that dietary MOS could improve growth performance and increase the resistance against NH3 stress in L vannamei, and the 2.0-4.0 g kg(-1) MOS supplementation was suitable for L. vannamei. (C) 2012 Published by Elsevier Ltd.