Strain RB51 is a live attenuated B. abortus vaccine approved in Brazil for use in adult cattle with full calf dose (1.3 × 1010CFU/dose)(Brasil, 2007). B.abortus Strain RB51 was not isolated from milk samples. Results in a reduction of sensitivity of the diagnosis,colonies,and consequently from use of selective media for direct plating of suspected sample could reduce the number of Brucella spp. Enrichment in tryptose broth supplemented with antimicrobials (Farrell’s supplement) was used before plating for improving the sensitivity of the culture, reducing false-negative results, This approach is reported to enhance the rate of isolation of B. abortus from infected animals by 50%, an analytical sensitivity of 200 B. abortus CFUs/mL of milk (data not shown) and increase the sensitivity of detection of B. abortus