Use of probiotic bacteria as growth promoters, anti-bacterial and their effects on physiological parameters of Oreochromis niloticus
Yassir A. E. Khattab 1, Adel M. E. Shalaby2 and Azza, Abdel-Rhman3
1- Fish Nutrition Department. 2- Fish Physiology and Hatchery Department.
3- Fish Disease Department. Central Laboratory for Aquaculture Research, Abbassa, Abo- Hammad, Sharkia.
Key words: Nile tilapia, growth, FCR, PER, haematology, probiotics, antibacteria, Aeromonas hydrophila, Micrococcus luteus and Pseudomonas species.
Micrococcus luteus and Pseudomonas species were isolated from gonads and intestine of apparantly healthy Oreochrois niloticus respectively. M. luteus and Ps. species were safe for O niloticus and had antagonistic effect against the pathogenic Aeromonas hydrophila (the cause of motile aeromonas septicemia among freshwater fish) in vitro. The inhibition zone was 4 cm in diameter with M. luteus and 9 cm in diameter with Psuedomonas sp. The effect of supplemental dietary probiotic bacteria (M. luteus and Ps. species, 107 cells per gram food) used as anti-bacterial on some physiological parameters, growth performance and survival rate of O. niloticus was also studied. Nile tilapia (2.35 - 2.45 g) were assigned to four treatments, with three replicates each. Fish were fed frequently a diet of 30% crude protein (CP) at a rate of 3% of live body weight twice daily for six days a week for 90 days. The obtained results showed that the final weight, weight gain and specific growth rate of O. niloticus increased significantly in fish fed with diet containing M. luteus, while they were decreased significantly in fish fed a diet containing Psuedomonas sp, when compared to the control group. The highest growth performance was recorded with M. luteus. Fish survival rate was decreased in fish fed with diet containing P. species. Feed intake was similar except for the fish that were fed M. luteus. The best feed conversion ratio (FCR) was observed with the fish fed M . luteus. There was no significant differences in protein efficiency ratio (PER) except that containing Psuedomonas sp. Crude protein content in whole fish body was significantly increased in fish fed with a diet containing a mixture of the two bacteria species, while total lipids were decreased significantly in all treatments. Ash content in whole fish body was significantly increased in all treatments. Erythrocyte counts (RBCs) in fish fed diets containing Micrococcus luteus were significantly higher than that of the control, but the RBCs and haemoglobin content (Hb) were decreased significantly in fish fed with the diet containing Psuedomonas sp.. Haematocrit values (Hct) were decreased significantly in all treatments. Also, the plasma total protein, aspartate amiontransferase (AST). Alanine amionotransferase (ALT) and lactate dehydrogease (LDH) were significantly decreased in fish fed with all diets containing Psuedomonas sp. On the other hand, the glucose concentration increased in all treated groups.
After the O. niloticus challenged by Aremonas hydrophila 0.3×107 cells / ml i.p.route, the mortality rate was 25% with M. luteus while Ps. species 90 %. The mixed group had mortality rate 80% as the control one. M. luteus was safe to O. niloticus and had probiotic effect in vitro and in vivo, while Ps. species had probiotic effect invitro only.