Intramammary immunization was investigated as a procedure to reduce the cli
nical signs of coliform mastitis. Twenty-four cows were equally distributed
to the following Escherichia coli 55 immunization schedules: 1) Subcutaneo
us injection 14 d prior to the end of lactation, intramammary immunization
7 d after drying off, and subcutaneous injection 30 d into the dry period;
2) subcutaneous injections at drying off, at 30 d into the dry period, and
within 12 h after calving; and 3) unimmunized controls. Intramammary immuni
zations were the infusion of vaccine via the teat canal into each of the fo
ur mammary glands. Cows were challenged by infusion of E. coli 727 into one
uninfected mammary quarter at approximately 30 d after calving. Intramamma
ry immunization enhanced antibody titers against E. coli 55 and E. coli 727
compared with subcutaneous immunization. Immunoglobulin G titers against E
. coli 55 and E. coli 727 in whey were greater at the time of challenge and
7 d after challenge for cows that received the intramammary immunization t
han for cows immunized by only subcutaneous injections. Serum IgG titers ag
ainst E. coli 727 were enhanced at 7 d after challenge for cows receiving i
ntramammary immunizations compared with conventionally immunized cows. Seru
m IgM titers against E. coli 727 were higher at calving for cows receiving
intramammary immunization compared with conventionally immunized cows. Immu
nization schedule had minimal effect on systemic and local signs of clinica
l mastitis following challenge.