Effect of hyperimmunization with an Escherichia coli J5 bacterin in adult lactating dairy cows.

Objective: To determine the effect of hyperimmunization with an Escherichia coli J5 bacterin on serum IgG2 concentration, incidence of clinical mastitis, and rate of survival to the end of the lactation period (ie, day 305) in adult lactating dairy cattle.

Design: Randomized controlled trial.

Animals: 1,012 Holstein cows in their second lactation and greater.