The primary immunoglobulin in cow colostrum and milk is IgG, whereas the primary immunoglobulin in human milk is IgA [1] . Nevertheless, bovine IgG from colostrum or milk can be effective as a means of providing passive immunity to protect animals and humans from disease. The use of bovine colostral immunoglobulin preparations from immunized cows for disease protection of the neonate of other species has been demonstrated in swine [47] , and experimental animal models such as mice [48, 49] . There also are a number of examples of the use of bovine immune milk products in the treatment or prevention of human disease, especially in cases where the pathogen acts by way of the gastrointestinal tract. When considering these studies, it should always be kept in mind that the colostrum or milk preparations potentially contain other immune modulating substances than immunoglobulins, as discussed briefly below (section 6.3).