Colibacillosis is a common infection in broilers and broilers breeder’s flocks caused by avian pathogenic E.coli (APEC) and resulting in major economic losses. Mortality, the cost of treatment and the decrease  in  feed  conversion  efficiency  result  in significant economic losses  cost to the poultry industry.  Clinical signs of colibacillosis can be observed in form of high mortalities, respiratory manifestations and poor growth rate. The pathogenicity of E.coli is depending on