K. Takemura, J. Lin, K. L. Smith, and J. S.
Hogan1
The Ohio State University Department of Animal Sciences
Abstract
Effects of immunizing dairy cows with FecA were investigated in an experimental challenge trial. Twenty-one cows were assigned to seven blocks of three cows based on expected parturition. Cows within a block were randomly assigned to either FecA immunization, Escherichia coli J5 immunization, or unimmunized controls. Immunization schedules were subcutaneous injection at 14 days prior to drying off, intramammary infusion at 7 days after drying off, and subcutaneous injection at 28 days after drying off. Bacterial challenge was by infusion of approximately 50 cfu of Escherichia coli 727 into one uninfected mammary gland between 13 and 31 days after parturition. Cows within a block were challenged on the same day. The FecA immunized cows had reduced clinical severity in challenged quarters and shorter duration of clinical symptoms compared with E. coli J5 immunized and control cows. The FecA immunized cows tended to have lower bacterial counts in milk, shorter duration of infections, and lower rectal temperature compared with E. coli J5 immunized and control cows. Milk SCC were similar among treatments. Milk production and dry matter intake did not differ among treatments. The FecA immunized cows had higher immuno globulin G (IgG) titers against FecA in serum and in mammary secretions compared with E. coli J5 immunized and control cows. The FecA immunization also increased IgG titers against whole-cell E. coli 727 antigen in serum and in mammary secretions compared with other treatments. Immunoglobulin G titers in mammary secretions against FecA immediately prior to challenge were negatively associated with peak rectal temperatures. Serum IgG titers against FecA at 7 days after challenges were negatively associated with peak temperatures and with peak bacterial counts. The FecA was immunogenic in cows and the antibody response was related to reduced clinical signs following experimental E. coli intramammary infections.