Some Factors Affecting Salmonella typhimurium Infection and Shedding in Chickens Raised on Litter

Abstract

Inapparent Salmonella typhimurium infection of chickens placed at different ages on contaminated pinewood-shavings litter was studied in three sequential trials. The numbers of S. typhimurium in the litter and in the ceca and feces of infected chickens were determined at regular intervals. Infected birds were identified as those harboring S. typhimurium in their ceca. Fecal cultures were more sensitive than cloacal swabs for the detection of shedders. Infection spread rapidly through chicks on new litter contaminated by infected seeders. As the flock matured, fewer birds examined were infected, and the number of organisms in their ceca and feces decreased. After 87 days, 36/59 were infected, 7 were shedding, and the litter contained 104 S. typhimurium per gram. Thirty-three-day-old chickens placed on this litter readily became infected; 28 days later, although the number of S. typhimurium in the litter had fallen to 102 per gram, 28/80 birds were infected, and 8 were shedding. Two days later, 63-day-old chickens were placed on this 131-day-old litter, and 32 days later, 41/50 birds were infected and 23 were shedding, although the litter contained only 102 organisms per gram. Removing infected 24-day-old chicks to a wire cage hastened the age-related decline in fecal excretion of S. typhimurium. Subjecting chickens to transport stress (crowding, motion, chilling, and food and water deprivation) did not increase shedding or detectable infection, although the average weights of both cecal and cloacal contents increased.