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Articles by P.S. Holt
Total Records ( 2 ) for P.S. Holt
  J.S. Bailey , A. Rolon , C.L. Hofacre , P.S. Holt , J. L. Wilson , D .E. Cosby , L. J. Richardson and N. A. Cox
  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 107 cells of a 3-strain mixture of antibiotic-resistant salmonellae. Chicks from eggs laid at 29, 34 and 40 wks of age were randomly divided into two groups, one group received a CE treatment by oral gavage. Both groups were given 107 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.
  J.S. Bailey , A. Rolón , P.S. Holt , C.L. Hofacre , J.L. Wilson , D.E. Cosby , L.J. Richardson and N.A. Cox
  Although vaccination against Salmonella has been used more frequently in broiler breeders in recent years, there is limited information in the literature demonstrating the immunological response of combinations of live and killed whole cell vaccines. The present research assesses the immunological response generated by three different vaccination protocols. Treatment vaccines consisted of a live Aro-A mutant commercial Salmonella Typhimurium (ST) vaccine (Fort Dodge Animal Health) and a commercially prepared killed vaccine consisting of a pool of Salmonella serovars Berta (D1), Heidelberg (B) and Kentucky (C2). Three vaccination treatments using live, killed or a live-killed combination plus a non-vaccinated control were evaluated. Serum (SER), Crop Lavage (CL), Gut Lavage (GL), hatchling serum and egg yolk were tested for specific IgA and IgG anti-Salmonella Enteritidis (SE) or Salmonella Typhimurium lipopolysaccharide (SELPS or STLPS, respectively) antigen by indirect ELISA. Immunological response was stronger on STLPS than SELPS. IgA of SER and CL were short-lived peaks after the first killed vaccine, with Optical Densities (OD) greater than 1.000. A short-lived peak of IgG of CL on STLPS (OD>1.500) was also observed. Strong GL IgG after first live and both killed vaccine events were observed (OD>1.000), with the response to the killed preparation enduring longer. SER IgG responses observed after killed vaccination lasted throughout 40 wks of age with no demonstrable differences between treatments. Hatchling serum and egg yolk IgA were negligible and IgG was comparable among all treatments throughout time. Results confirm that killed antigen is vital in eliciting adequate IgG in serum and gut. Live vaccination with Aro-A mutant ST vaccine enhances gut IgG and possibly aids in conferring adequate immunity during the breeder's first wks of life
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