A Comparison of Sites Colonized in Broilers Challenged Through Various Routes and Feed Administration with Salmonella Enteritidis and Salmonella Heidelberg at Day 14
Type of DegreeMaster's Thesis
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Salmonella Enteritidis (SE) and Salmonella Heidelberg (SH) are among the top Salmonella serovars associated with poultry. Broiler grow-out facilities may contain these organisms and can be introduced to the broiler through contact with the environment, utilizing various body cavities for entry. For successful reduction or elimination of these organisms during the harvest and post- harvest period, greater attention must be placed on evaluation of the portals of entry utilized by the organism and the tissues colonized during the preharvest period. The objectives of the three experimental groups (Group 1: SE experiments; Group 2: SH experiments; Group 3: SE vs SH experiment) were to determine: (1) the effect of different inoculation routes (oral, cloacal, intratracheal, ocular, and subcutaneous) on tissue colonization of Salmonella (Groups 1 & 2), (2) the effect of the two serovars used on feed administration (Group 3), and (3) to determine Salmonella incidence within sampled organs (Groups 1-3) when challenged on d 14. For Groups 1 & 2, the birds were challenged with 1 x 104 colony forming units (CFU)/ bird at d 14 through the above-mentioned inoculation routes. For Group 3, pens were each given access to 15.87 kg of 1 x 104 CFU/g of SE or SH inoculated feed. This feed was fully consumed in approximately six to seven days before re-exposure to non-inoculated feed. The following ten tissue samples were collected from 100 birds approximately 21 days post inoculation: breast, bursa and thymus (pooled), ceca, crop, kidney, liver and spleen (pooled), skin, spinal cord, thigh, and trachea. Additionally, four swab samples were taken from the abdominal cavity, bone marrow, cloaca, and lung. For Groups 1 & 2, data were analyzed using General Linear Model procedure and for Group 3 data was analyzed using an independent t- test. Differences were reported at P ≤ 0.05, and if applicable, means were separated using Tukey’s HSD. The ocular route produced the greatest percentage of Salmonella positive birds and its incidence within the samples (Groups 1 & 2). The birds challenged with SE contaminated feed produced the greatest number of positive birds and positive samples within the body (Group 3). Results from each of the studies varied considerably; however, samples most often affected include the ceca, crop, cloaca swab, bursa and thymus, skin, and trachea (Groups 1-3). Differences in incidence between serovars may be attributed to the isolate used and pathogenicity of the organism influencing survival, establishment, colonization, and invasion in the bird. With the greatest effect occurring in birds challenged through the ocular route, greater attention should be placed on evaluation of this route as a mode of transmission.