In domestic animals brucellosis has been commonly known as enzootic abortion, epizootic abortion, infectious abortion, contagious abortion, slinking of calves, Bang’s disease, or ram epididymitis. Brucellosis is an infectious, contagious disease caused by bacteria of the genus Brucella; it primarily affects cattle, sheep, goats, swine, and dogs and is characterized by abortion or infertility. A wide variety of media have been used for cultivation of brucellae. Most laboratories today use a tryptose or trypticase soy agar containing added serum for primary isolation of Brucella. Brucella metabolism is primarily oxidative and requires multiple amino acids, thiamine, biotin, and nicotinamide for growth. Virulent Brucella are highly invasive and are capable of penetrating mucous membranes of the nose and throat, conjunctiva, urogenital tract, teat canal, and normal or abraded skin. Natural host defenses against Brucella play an important role in protecting animals against infection. Such natural defenses probably account for the variance in host susceptibilities to different Brucella species.