A variety of probiotic bacteria have been tested to control animal and foodborne pathogenic bacteria in livestock. The mechanism of inhibition of pathogenic bacteria for several of those probiotic microorganisms is mediated by the production of bacteriocins. Colicins are probably the group of bacteriocins that have been most thoroughly characterized. Colicins are antimicrobial proteins produced by one strains of Escherichia coli to suppress the growth of other strains of E.coli. The present study indicated the preparation of colicin from colicinogenic bacteria. A total of three hundred rectal and rumen swabs isolated from health and diarrheic calves located in Fars province feces. One hundred and fifteen strains were confirmed as E.coli by biochemical test. Polymerase chain reaction was used to determine the following genes encoding colicins. Nearly 100% of isolates were contained at least one gene of colicin. The frequency of several classes of colicin was determined. As a result the most detected gene was Ia Ib and the least detected gene was A.N.S4. Colicin should be tested to control animal and foodborne pathogenic bacteria in livestock.