The experimental work of the present study was carried out in the rabbit’s farm of Department of Nutrition and Clinical Nutrition, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt from October to December 2008.A total number of 56 weanling New Zealand rabbits of 35 day old, were divided into seven groups (8 each). The first group was used as a control and other groups supplemented with different types of feed with addition of enzyme to some groups as following The experimental rations were offered ad \libitum twice daily. Rabbits were individually weighted to the nearest gram every week. At the end of experimental period, three representative rabbit’s samples from each feeding group were randomly taken to studyTen digestion trials were conducted to determine the digestion coefficient of nutrients and nutritive value of the experimental diets.Also, three caecum samples from each group after slaughter were taken to determine cecum pH, Ammonia and total volatile fatty acid.The obtained results are summarized as follows:A. Growth performance:probiotics).The collected samples were examined for determining theprevalence of Salmonella serotypes. Experimental study was done toevaluate the effect of probiotics (Lypholac & Sambiogen) on occuranceand mean count of S.typhimurium in caecum of healthy and experimentallyinfected broilers with S.typhimurium strains. Also, the effect of previousprobiotics on broiler performance with and without S.typhumuriuminfection was conducted.The obtained results were summarized as follows:1- Examination of 260 cloacal swabs, water, feed and litter samplescollected from three broiler farms without using probiotic at Sharkiagovernorate, Salmonella was recovered from 7 samples with overallprevalence 2.69%. Moreover, the overall percentages of Salmonella in thefarm No. 1, 2 and 3 were 3%, 2.5% and 2.5% respectively. The serotypingof respective isolated Salmonella strains was identified as five strainsS.entritidis and two strains S.agama.Generally, Salmonella was isolated from cloacal swabs, feed andlitter in a percentage of 42.86% (3 out of 7), 14.29% Cl out of 7) and42.85% (3 out of 7) respectively, but no Salmonella was detected inexamined water samples. Three isolate recovered from cloacal swab wasrepresented as one isolate S.Entritidis and other two was S.Agama, but .