A bovine IgG-enriched whey fraction contains antibodies against various bacterial antigens. We investigated the protective effects of a bovine whey fraction preparation against infections with Enterohaemorrhagic O157:H7, serovar Enteritidis, and in mouse models. After infection with these pathogens, the IgG-enriched fraction or skim milk was given ad libitum at a 5% solution instead of water. The mice given the IgG-enriched fraction were significantly resistant to orally challenged EHEC O157:H7 (LD: 4.0 × 10 CFU/mouse) infections compared with the mice given skim milk (LD: <1.5 × 10 CFU/mouse). The mice given the IgG-enriched fraction were also significantly resistant to orally challenged  Enteritidis (LD: 5.0 × 10 CFU/mouse) infections compared with the mice given skim milk (LD: <2.5 × 10 CFU/mouse). When the mice were nasally infected with , the numbers of the bacteria in lungs of mice given the IgG-enriched fraction were significantly lower than those given skim milk 2 and 3 weeks after infection. These results strongly indicate that oral administration of the bovine IgG-enriched whey fraction protects mice against food-borne infection and also that it partially protects mice against respiratory tract infection.