Objective: To determine whether vaccination of lactating cattle with an Escherichia coli J5 bacterin-toxoid would produce a significant short-term change in milk production.
Design: Randomized, controlled clinical trial.
Animals: 84 healthy, lactating cows (42 Holsteins and 42 Jerseys).
Procedure: Control and vaccinated cows were paired on the basis of breed, days in milk, daily milk production 1 week prior to vaccination, and parity. One cow in each pair was inoculated IM with a commercially available bacterin-toxoid according to label directions; the other cow was given saline solution. Cows were milked twice daily for 5 days before and 5 days after inoculation. Milk production was compared by ANCOVA.
Results: Vaccinated cows produced significantly less milk than did control cows at the second and third milkings after inoculation. At these milkings, milk production in vaccinated cows was approximately 7% less than that of controls.
Clinical implications: Vaccination of lactating cattle with an E coli J5 bacterin-toxoid may cause a significant short-term decrease in milk production.