Field studies on the new combination of antibiotics for the control of bovine Mycoplasmas and Ureaplasmas have been critically evaluated on bovine semen. Reference strains of Mycoplasmas and Ureaplasmas were standardized to 10^5 to 10^6 CFU (Colony Forming Units) and inoculated into raw semen. Then antibiotic combinations were added in each concentration on heated milk extender. Also, field samples were collected and treated with the combinations. The combinations of gentamicin (500㎍/ml) tylosin (100㎍ /ml) and Lincospectinomycin (300/600㎍/ml) has been proven to be very effective on the control of infections bacterial organismes of bovine semen for artificial insemination.