F-1- Feeding culture system design:
The feeding experiment was conducted in 8 glasses aquaria (75×40×50 cm), at the Center Laboratory of
hydrobiology department, Veterinary division, National Research Centre, Egypt. The aquaria were supplied with
aerated tap water. Each aquarium was supplied by airiator. Fresh tap water was stored in cylindrical fiberglass
tanks for 24 hours under areation in order to dechlorenated the water. Each aquarium was cleaned daily by
siphoning fish feces and remaining feed with 75% of total water volume, then refilled to fixed volume again.
Water temperature range was (29- 32ºC).
Nile tilapias, O. niloticus with an average weight (22±2.23) were acclimatized in indoor glass aquaria for
two weeks. The fish were distributed randomly at a rate of 20 fish / aquarium. Treatments in triplicate were
arranged at random. The experimental fish were batch weighed at the beginning of the experimental period.
Probiotic cell suspension was added to the feed as 5gm ∕ kg feed and fish were fed once daily for 6 days a week,
at a fixed feeding rate of 3% body weight of fish per day. The experiment was run for 30 days, and then the
bacterial challenge was carried out.