Efficacy of an Escherichia coli J5 bacterin administered to primigravid heifers

The efficacy of an Escherichia coli J5 bacterin for reducing the incidence of intramammary infections and clinical signs of mastitis was tested in fir st lactation heifers. Ten primigravid heifers were immunized with an E. col i J5 bacterin. Four heifers received a placebo. The bacterin and placebo we re injected subcutaneously approximately 60 d prior to calving, 28 d later, and within 48 h after calving. Vaccinated and placebo-injected heifers wer e challenged by intramammary infusion off. coli 727 in one mammary gland be tween 23 and 37 d after calving. All challenged quarters were diagnosed wit h an intramammary infection within 6 h after bacteria were infused. The sev erity and duration of local signs of clinical mastitis were reduced in vacc inated heifers compared with placebo-injected heifers. Systemic signs of cl inical mastitis were limited and did not differ between treatment groups. B acteria counts in milk from challenged quarters were lower in vaccinated he ifers than in control heifers at 12, 15, and 48 h after challenge. Serum im munoglobulin G titers against whole-cell E. coli J5 antigen at calving were higher in vaccinated heifers than they were in-controls. Vaccinated heifer s had higher immunoglobulin G titers than did controls in mammary secretion s at calving and immediately prior to challenge. Immunization of primigravi d heifers with an E. coli J5 bacterin during the last trimester of gestatio n and at calving reduced the severity and duration of clinical signs follow ing intramammary challenge with a heterologous strain of E. coli.