Characterization of specific passive immunity stimulated by vaccination of beef cows grazing native range with E. coli O157:H7-SRP®.

A total of 20 four-year-old, mixed breed cows were selected from the Kansas State University commercial cow-calf herd for this study. Cows were assigned randomly to one of two treatments: placebo, or E. coli O157:H7 SRP® (Epitopix LLC, Wilmar, MN) vaccination prior to calving. Serum total protein (TP) and serum Escherichia coli O157:H7 SRP® antibody levels (SRP) were measured pre-suckle and at set intervals post-suckle in calves. All 20 cows were negative for fecal shedding of E. coli O157:H7 throughout the study. Vaccination of cows had no effect on calf serum TP level (P > 0.05) compared to controls, however, length of time post-birth had a significant effect on calf serum TP levels (P < 0.001). Failure of passive transfer was recognized as early as six hours post-birth. A vaccine treatment by time post-birth interaction was observed for calf serum SRP® antibody levels (P < 0.01). Calves born to dams vaccinated with E. coli O157:H7 SRP® vaccine had elevated serum SRP antibody titers over time compared to placebo vaccinated calves. This study demonstrated that successful E.coli O157:H7 SRP® antibody passive transfer can occur in beef calves under natural range conditions. This could be the first step toward understanding life cycle immunization strategies against E. coli O157:H7 in cattle, and its effects on shedding of the organism by the animal at the time of harvest.