Abstract Aims: The purpose of this investigation is to use the Ziziphora Powder and a commercial probiotic (lactofeed) (LP) on performance. Material & Methods: A total of 320 male, one-day-old chicks (Ross 308) were fed completely randomly in 8 experimental groups and 4 replications and each replication, 10 chickens. The experiment has been done from 1 to 42 days old. The experimental groups consisted of group 1 or control group: basal diet (without any feed additives), group 2: basal diet with 1.5% of ZP, group 3: basal diet with 1% ZP, group 4: basal diet with 0.02% of LP, group5: basal diet with dexamthason (DEXA), group 6: basal diet with 1.5% of ZP and dexa, group 7: basal diet with 1% ZP and dexa, group 8: basal diet with 0.02% of LP and dexa. Results: According to the results of this experiment, it was observed that in the first week, 1% of ZP caused an increase in weight, and in the second week, 1.5% of ZP had a significant increase in weight compared to 1% of ZP with dexamethasone injection and, the results showed the Ziziphora Powder plus dexa increased the gizzard and liver weights. Although the lactofeed was decreased pancreas weight. In population of cacum the highest bacterial coumt (e.coli and salmonella spp.) showed in dexa groups and the lactofed groups lowest of them. Conclusion: Dexamethasone injection increased the feed consumption in the whole period and significantly increased the FCR and also caused a significant weight loss, and increased the bacterial population in cecum, in the whole period and significantly increased the gizzard and liver weights. compared to the treatments without dexamethasone.
