A doctoral thesis in the Department of Animal Production at the College of Agriculture at the University of Basra discussed the effect of using the preparation made from lactic acid bacteria isolated from the intestines of adult chickens on some productive, physiological and microbial characteristics of laying hens and broilers. The thesis submitted by the student Ahmed Ali Kazem Al-Salihi, which was carried out under the supervision of Assistant Professor Dr. Qutaiba Jassim Ghani Al-Khafaji and Professor Dr. Sabah Malik Habib Al-Shatti, included three extensive scientific experiments, as the first laboratory experiment (microbiological) was conducted in the Microbiology Laboratory of the Department of Food Sciences ; To isolate a group of lactic acid bacteria strains and register them at the National Center for Biotechnology Information NCBI and manufacture a preparation of lactic acid bacteria isolated from the intestines of adult chickens, and apply it to laying hens and broilers, in two separate experiments. The thesis aimed to manufacture a bacterial preparation, to be a safe alternative to imported antibiotics and probiotics, in support of the national economy and to reduce the side effects resulting from the use of antibiotics that are reflected on the health of the consumer. The thesis concluded: that enhancing the natural intestinal flora of laying hens and broilers with different levels of the manufactured bacterial preparation has effectively contributed to creating a microbial balance; As a result of the competitive exclusion in obtaining binding sites for cell receptors of the intestinal wall, which contributes to the expulsion of large numbers of harmful bacteria from the gut, and thus improve the microbial characteristics, which is ultimately reflected in the improvement of the productive and physiological performance of poultry.