To investigate the impact of dexamethazone (Dx) with or without spiramycin (Sp.) in controlling the mortality rate of broiler farms infected with infectious bronchitis (IB), two experiments were conducted. In the first pilot experiment, 750 broiler chicks (Ross) were divided into control (C) and two treated groups received Dx and Sp (G1) or only Sp (G2), respectively. Second experiment was conducted on five selected broiler farms (6000 chicks each), two farms were kept without treatment as a

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... trol, whereas other farms were treated with a combination of Dx and Sp. All birds were vaccinated against Newcastle disease (ND), avian influenza (AI), infectious bronchitis (IB) and infectious bursa disease (IBD), and monitored throughout the experiment to detect any respiratory sings. The treatment protocol was started when respiratory sings appear. Blood samples were collected at day 5 of treatment from jugular vein and serum was to assess aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) and to detect the antibody titer for the deferent vaccines by ELISA. The result showed significant decrease of mortality rate in G1 group among experimental groups and insignificant differences of liver function tests and immune response to the vaccination against ND and AI. It can be concluded that using a combination of dexamethasone and spiramycin has an efficient effect to protect broiler chicks against infectious bronchitis by decreasing the mortality rate with no immune suppression.