A third experiment to evaluate effect of 0.2% dietary chitosan on ST horizontal transmission was done. Chickens were randomly assigned to untreated control diet (n=50) or treatment with 0.2% chitosan (n=50) for 10 days. Chicks were housed in floor pens with feed and water provided ad libitum. On day 3, 10 birds per group were challenged with 105 CFU ST/bird to act as seeders, while the other 40 birds per group were contacts challenged by horizontal transmission from the seeders. At 10 days of age, 10 seeders and 20 contact chicks were humanely killed by CO2 inhalation; ceca and cecal tonsils were aseptically harvested and cultured for ST recovery.