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Title: Resistance to Challenge of Breeders and Their Progeny with and without Competitive Exclusion Treatment to Salmonella Vaccination Programs in Broiler Breeders

item Bailey, Joseph
item Holt, Peter
item Cosby, Douglas
item Richardson, Larry
item Cox Jr, Nelson

Submitted to: International Journal of Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2007
Publication Date: 6/1/2007
Citation: Bailey, J.S., Rolon, A., Hofacre, C.L., Holt, P.S., Wilson, J.L., Cosby, D.E., Richardson, L.J., Cox Jr, N.A. 2007. Resistance to Challenge of Breeders and Their Progeny with and without Competitive Exclusion Treatment to Salmonella Vaccination Programs in Broiler Breeders. International Journal of Poultry Science. 6(6):386-392.

Interpretive Summary: Salmonella in broiler chickens continues to be a primary concern for regulatory and public health agencies and the U.S. Poultry Industry and these groups acknowledge the need to develop effective on-farm intervention strategies to reduce consumer exposure to Salmonella. Different combinations of live and killed cell Salmonella vaccines were administered in a commercial operation to broiler breeders. The immunological response was measured in breeder birds and the response to Salmonella colonization was measured in their progeny. Vaccine treatments were shown to elicit an immunological response in breeders and progeny, but progeny were not protected from Salmonella colonization unless a live vaccine was administered. Data from this study will allow poultry producers and vaccine companies to make scientifically proven informed decisions about the best times and types of vaccination treatments to help reduce Salmonella in broiler breeders.

Technical Abstract: Resistance to Salmonella challenge of breeders under three vaccination programs and of their chicks with and without mucosal competitive exclusion (CE) (CHR Hansen) treatment was assessed. Vaccine treatments combined a live Aro-A Salmonella Typhimurium (ST) vaccine and an autogenous commercially prepared (Lohmann Animal Health) trivalent killed vaccine (serogroups B, C2 and D1). Treatments combined: 2 live and 2 killed doses or 3 live and 1 killed dose delivered at 1, 21, 77 and 126 d of age; or 2 killed doses delivered at 77 and 126 of age; and a non-vaccinated control (C). At 3, 6, 11, 17 and 22 wks of age, a portion of breeder pullets was removed and challenged per os with 10/7 cells of a 3-strain mixture of antibiotic-resistant Salmonellae. Chicks from eggs laid at 29, 34 and 40 wks of age were challenged at 1 d of age with and without CE pre-treatment, with 10/7 cells of a 2-strain mixture of antibiotic-resistant Salmonellae and kept in isolation units for one and two wks. Ceca and Liver-Heart-Spleen (LHS) samples were cultured for each strain on BGS + antibiotic plates and colonies enumerated. Log10 data were analyzed under factorial designs. Breeder Salmonella counts showed significant reductions between (live) vaccinates and non-vaccinates at 3 (0.82 log) and 6 wks (0.85 log) challenges. By 11 wks, there were no differences in Salmonella levels between vaccinates and controls, indicating that 1-d and 3-wk live vaccine protection had diminished with time. All vaccination treatments reduced breeder cecal counts (1.15-1.30 log) by wk 22. Passive immunity from breeder vaccination treatments was not effective in diminishing chick cecal counts as shown by comparable susceptibility of chicks from vaccinated and control breeders, regardless of breeder age. Chick CE treatment consistently diminished cecal (1.41 log) and LHS (0.306 log) counts. These results show that live Aro-A ST vaccination decreases counts during the first 6 wks of age, as do all programs by 22 wks of age, and that competitive exclusion is the most effective treatment in reducing hatchling Salmonella counts.