Effects of b-glucan on the growth, survival, and the efficacy of Anti-streptococcus iniae vaccine in rainbow trout (Onchorhynchus mykiss)

Glucans are complex polysaccharide components of yeast and fungal cell walls.This compounds can stimulate the fish immune system. The present study investigated the effects of Beta glucan(Macrogard) on growth, survival and some immunological parameters of rainbow trout (10 mg) and also on the efficiency of Streptococcus vaccine. Treatments of macrogard (1 g/kg food/day for 42 days), macrogard (macrogard 1 g/kg diet) with 15 minutes bathin vaccine, vaccine bath without macrogard and control were examined in a 42 daysperiod. In all treatments the fish growth (weight) showed a significant increase (p<0.05) compared to the control, while there was no significant difference among the treatments. The lyzosyme level of the blood serum showed a significant difference between control and the other treatments, the highest level was observed in the macrogaurd with vaccine treatment (2.7 µg/ml) and the lowest level was observed in the control(0.5 µg/ml). Leukocytes count also had a significant difference between the control (3.3%Nuetrophil) and other treatments (6.6% Nuetrophil) (p<0.05). The result of survival of fish challenged with Streptococcus iniae via bath route was 55%, while those for vaccine treatment, macrogard plus vaccine, macrogard every day and macrogard every 10 days interval were 75%, 86%, 60& and 55%, respectively. The results of this study showed that supplement of macrogard has positive effect on growth and non-specific immune responses of rainbow trout and can enhance efficacy of anti- streptococcus iniae vaccine in this fish.