Influence of age on the serological response of chickens to Salmonella typhimurium infection.

After chickens 1-126 days old were infected orally with Salmonella typhimurium, antibody responses were determined by microagglutination (MA) and microantiglobulin (MAG) test procedures. In all groups six weeks old or older, a high and continuing level of salmonella group B antibody was demonstrated by the MAG test but not by the MA test. Serological response was maximal at about 15 weeks or later. Reinoculation with S. typhimurium 129 days after initial infection elevated antibody titers in all groups, and immunological paralysis was evident in only the two youngest groups. S. typhimurium-positive cloacal swabs tended to decline rapidly in all groups; although MAG agglutinin titers remained positive.