Thesis (Ph.D.) - Cairo University - Faculty of Veterinary Medicine - Department of Microbiology

This research was initiated with the objective of producing a local probiotic formulation and application programs to further improve broiler production economics and safety. Four isolates of lactobacilli were recovered and characterized biochemically, and genetically, based on the rRNA gene from the gut of mature healthy broilers. L. johnsonii, L. plantarum, L. crispatus and L. reuteri were selected and mixed with an equal volume and approximate dose of 108 CFU/chick was tested. The safety of oral administration of the characterized lactobacilli was established in broilers. An innovative media from chicken feed for propagation of lactic acid producing bacteria was devised to reduce the cost of local commercial production of probiotics. A probiotic application protocol was suggested. Single and two-time probiotic applications (at 0 day or at 0 and 10 days) were tested in groups of broiler chicks reared under field conditions and fed antimicrobials- and anticoccidial- free rations. The modified whey broth surpasses MRS and feed extract media. Performance parameters and antibody immune responses were measured with, and without microbial challenge in two experiments. Clostridium perfringens type A was used in challenging bird (109 CFU/chick). Higher performance parameters, reduced disease impact and improved histopathological picture of intestine were reported in groups receiving probiotic. Non significant changes in antibody responses were observed. Data analysis shows that an overall 8% increase in broiler production can be achieved using the double dose application approach of the probiotics. A significant (P {u2264} 0.05) risk reduction of C. perfringens challenge can be achieved using either one or double dose application approach of the probiotics and conclusions pertaining the use and possible production economics were drawn

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