A total number of 180 Nile-tilapia (Oreochromis niloticus) were divided into four equal
groups; the first one served as control fed on basal non-treated diet. The second group fed on
diet supplemented with 0.5 ml prebiotic βpolo /kg basal fish diet, the third group on diet
supplemented with 1 ml prebiotic βpolo/kg basal fish diet, and the fourth group fed on diet
supplemented with 1.5 ml prebiotic β polo/kg basal fish diet for 40 days. The result elevated
that, the growth performance was significantly higher in all treatments than in the control group
and the highest increased was in the group received 1.5 ml prebiotic βpolo /kg basal fish diet.
The hematocrit (HC) values, nitroblue-tetrazolium (NBT) and lysozyme activities were
increased significantly in all treated groups than the control and the highest increased was in
the group received 1.5 ml prebiotic βpolo /kg basal fish diet. The percent level of protection
among the three treated groups after challenge infection using Pseudomonas flourescence (Ps.
flourescence) (0.5 ml of culture suspension of pathogen containing 107 bacteria ml-1) was
higher than control and the highest record was in the group of received 1.5 ml prebiotic βpolo
/kg basal fish diet .