Immune response of medicated turkeys vaccinated with live Pasteurella multocida.

In 3 experiments, turkeys were vaccinated with the Clemson University strain of Pasteurella multocids (CU) via the drinking water for 1 or 3 days while they were fed 3 different rations. Ration 0X consisted of non-medicated turkey starter, ration 1X had 0.00625% sulfadimethoxine and 0.00375% ormetoprim added, and ration 2X had 0.0125% sulfadimethoxine and 0.0075% ormetoprim. Immune response was determined by challenge exposure with pathogenic P multocida, either serotype 3 or serotype 4, administered for 3 days via the drinking water. In experiment 1, the 1X concentration of medication reduced protective immunity by 30%. In experiment 3, the reduction was 37% for the 1X concentration and 45% for the 2X concentration. The increased concentration of medication was more efficacious in preventing infection in vaccinated and nonvaccinated turkeys.