Sensitivity of Young Chickens to Salmonella typhimurium var. copenhagen and S. infantis Infection and the Preventive Effect of Cultured Intestinal Microflora

Abstract

The sensitivity of 1 day old chickens to S. infantis and S. typhimurium var. copenhagen infections was determined. The calculated ID50 [median infective dose] values in different trials were 22.4 and 2.6 S infantis organisms and 0.46 and 6.1 S. typhimurium var. copenhagen organisms. The protective capacity of cultured cecal microflora to prevent S. infantis infection was examined. The chickens were infected with different dose schedules at different intervals. The culture given to the newly hatched chickens before challenge increased their resistance. The level of resistance provided by the treatment was about as high as that of the 2 wk old chickens in normal life. Protection was poor when the culture was given simultaneously with the challenge and was absent when given after challenge.