Field trial comparing three oral application methods for a live Salmonella Typhimurium vaccine in broiler chicks

Abstract Live vaccines have been a significant factor in reducing Salmonella prevalence in European poultry flocks. As newly hatched chicks are most susceptible to infection, it is important to administer the first dose as early as possible. In a field trial, three oral application methods were compared for their efficacy in terms of vaccine uptake by day-of-hatch broiler chicks receiving a live S. Typhimurium vaccine. Broiler chicks were placed in three houses on one commercial broiler farm on the day-of-hatch. All came from the same hatchery and were the offspring of a single breeding flock. Birds in Group 1 were vaccinated with a live S. Typhimurium vaccine via the drinking water line according to manufacturer’s recommendations. In Group 2, feed was laid out on paper on the floor, and the vaccine was mixed with a gel (Agrivite Prostart Chick Gel) which was then spread over the feed. Chicks consumed the gel within the first two hours after placement. In Group 3, the vaccine was mixed with a spray-gel (Hatch Gel SP,) which was sprayed onto the chicks using a knapsack sprayer. Chicks consumed the gel by preening each other within the first few hours. Two days post-vaccination, vaccine uptake was determined in caecal contents and liver tissues of 30 birds/group by quantitative bacteriology. All 90 birds successfully took up the vaccine with quantifiable levels in both caecal and liver samples. Geometric mean levels (cfu/g) in caecal contents were 2.9 x 10 6 (Gp1), 1.3 x 10 7 (Gp2) and 1.3 x 10 8 (Gp3), and in liver samples levels were 6.6 x 10 2 (Gp1), 1.7 x 10 2 (Gp2) and 1.1 x 10 2 (Gp3). Levels in caecal contents were highest in the group receiving the vaccine in the spray gel, whereas levels in liver tissue were highest in the drinking water group. To conclude, all three application methods resulted in excellent vaccine uptake in all birds examined, showing that vaccination of broilers as early as day-of-hatch can be achieved using any of the methods investigated. Vaccination upon immediate arrival at farm is therefore readily achievable.