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Abstract
This study compares efficacy of various Salmonella bacterins following priming with two doses of live Salmonella Typhimurium vaccine in broiler breeders. Vaccination is one of the most practical measures to reduce Salmonella contamination of poultry and to prevent foodborne disease in humans. Commercial live and killed Salmonella vaccines have proven to be effective in commercial poultry production. This is supported by several field studies that have demonstrated vaccination increases Salmonella-specific antibody titers in vaccinated breeders and significantly reduces breeder colonization by challenge strains. In this study protection from commercially available live and inactivated Salmonella vaccine combinations were compared following challenge with three different serotypes of Salmonella. Broiler breeders were housed in a controlled setting of six pens; five pens were vaccinated with two doses of live Salmonella Typhimurium vaccine and four pens were also vaccinated with inactivated Salmonella vaccine containing whole cells of Salmonella Enteritidis, Salmonella Typhimurium and Salmonella Heidelberg. One pen was occupied with unvaccinated breeders that served as controls. At 10, 14, 20, 30, and 45 weeks of age twenty breeders from each treatment were challenged by oral gavage with Salmonella Enteritidis. In addition, protection passed to the progeny from the broiler breeders was assessed by collecting eggs from vaccinated and unvaccinated pens. Hatched chicks were placed into eighteen pens, three repetitions for each treatment group. Four progeny studies were done by challenging chicks by oral gavage with Salmonella Enteritidis, Salmonella Typhimurium, Salmonella Kentucky and Salmonella Heidelberg. Protection provided by vaccination of broiler breeders was assessed by bacterial culture of liver/spleen pool and ceca for Salmonella prevalence, most probable numbers (MPN) of ceca, and enzyme-linked immunosorbent assay (ELISA) using a combined SE/ST Biochek kit on serum and an IgA assay on crop and intestinal lavages. Salmonella prevalences and loads in broiler progeny were assessed by bacterial culture and MPN of ceca.