Antibodies Dynamics in the Broiler Digestive Tract after Salmonella Typhimurium Oral Challenge

This study aimed to provide directions for Salmonella challenge experiment conception by offering a better understanding of the relationship between age and mucosal immune responsiveness of chicken. Intestinal maternal immunity of Salmonella-free chicks was monitored by ELISA analyses at 2, 9 and 16 days of age. At 21 days of age, chicks were orally inoculated with Salmonella Typhimurium. Three inoculum doses (3 x 10E3, 3 x 10E6, 3 x 10E9 cfu/bird) and an uninfected control were then compared concerning mucosal immune status of the small intestine and cecum. Results suggest that difficulties encountered to infect very young chicks can be related, at least partly, to maternal immunity. The relatively low level of intestinal immune defences observed thereafter could indicate a right time to perform an experimental infection of birds and to maximize the spreading of the pathogen during challenge experiment. After infection of 3-week-old chickens, the mucosal immune response was rapid with increased anti-Salmonella Typhimurium IgA titers. There was a linear relationship between specific IgA levels in intestinal and cecal secretions and the challenge dose initially inoculated.