Influence of mannan oligosaccharide supplementation on haematological and immunological responses and disease resistance of striped catfish (Pangasianodon hypophthalmus Sauvage, 1878) juveniles

This study was carried out to evaluate the effect of mannan oligosacharide (MOS) as dietary supplement on haematological parameters, immune response and protection against Aeromonas hydrophila in striped catfish (Pangasianodon hypophthalmus, Sauvage, 1878) juveniles. Triplicate groups of juvenile striped catfish (initial weight 20.41 +/- 1.64 g) were fed twice per day at 2.5% of body weight for 12 weeks, with 0 (control), 0.2, 0.4, 0.6 or 0.8% MOS diets. At the end of the feeding trial, fish were intraperitoneally challenged with 1 x 10(6) CFU ml(-1)of A. hydrophila and mortalities were recorded over 21 days. The haematological and immunological parameters were assessed both in pre- and post-challenged fish groups. Dietary inclusion of MOS did not show any significant influence on the majority of the haematological parameters of striped catfish when they were not infected. But it showed a significant positive influence on some of the most important parameters, namely RBC, WBC, lymphocyte, granulocyte and lysozyme activity and survival, after a 2-week challenge with A. hydrophila. After 2-week infection with A. hydrophila, a better concentration of red blood cell (RBC), white blood cell (WBC), granulocyte, total Ig content, lysozyme activity and survival were observed when striped catfish were fed with MOS at 0.4% and above, with significantly highest at 0.6% MOS diet than the control diet. Based on the results of this study, it is concluded that supplementation of MOS at least 0.4% is sufficient to activate the immune response and makes the striped catfish more resistant to A. hydrophila infection.