|Cox, Nelson - Nac|
|Cook, Kimberly - Kim|
|RITZ, CASEY - University Of Georgia|
|Hinton, Jr, Arthur|
Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2019
Publication Date: 1/24/2020
Citation: Cox Jr, N.A., Oladeinde, A.A., Cook, K.L., Zock, G.S., Berrang, M.E., Ritz, C.W., Hinton Jr, A. 2020. Research Note: Evaluation of several inoculation procedures for colonization of day-old broiler chicks with Salmonella Heidelberg. Poultry Science. 99(3):1615-1617. https://doi.org/10.1016/j.psj.2019.10.020.
Interpretive Summary: Prior to doing a large bird trial, it would be helpful to know what method of inoculation would produce the greatest percentage of cecal colonized chicks and also which one would produce the highest level of colonization in the ceca. This study compared three methods of Salmonella challenge (oral gavage, intracloacal inoculation and a seeder bird approach). Results suggest that intracloacal is the method to use to ensure most of the challenged birds are colonized and oral gavage resulted in a smaller percentage of birds being colonized with higher levels.
Technical Abstract: Before starting a study with many birds, it helps to know the method of chick inoculation. The objective was to compare 3 methods of Salmonella challenge (oral gavage [OR], intracloacal inoculation [IC], and seeder bird [SB]). Day-old broiler chicks (n = 100) were inoculated with 106 colony forming units (CFU) per chick of a marker strain of Salmonella Heidelberg (SH) with each route of inoculation. Chicks (n = 25) inoculated by each route were placed in floor pens on fresh pine shavings litter. For the seeder batch, 5 colonized chicks, each orally gavaged with 106 CFUs, were placed with 20 pen mates. Two weeks after inoculation, 10 birds from each pen and the 5 inoculated seeder birds were euthanized, the ceca were aseptically removed and macerated with a rubber mallet and weighed, and 3 times (w/v) buffered peptone was added and stomached for 60 s. Serial dilutions were made and plated onto Brilliant Green Sulfa plates containing 200 ppm nalidixic acid. Plates were incubated along with the stomached ceca for 24 h at 37°C. If no colonies appeared on the plates, an additional plate was streaked from the preenriched bag and incubated for 24 h at 37°C. In addition to all seeder birds being positive, the number of SH-positive birds out of 20 sampled in each group was 13, 17, and 7 for OR, IC, and SB, respectively. The level of SH per g of ceca and cecal contents was log (SE) 3.0 (0.7), 2.0 (0.4), and 2.6 (0.4) for OR, IC, and SB, respectively. After enrichment, the number of colonized birds out of 20 was 18, 20, and 10 for OR, IC, and SB, respectively. In conclusion, this study suggests that IC is the method to use to ensure most of the challenged birds are colonized. However, if you prefer to have a smaller percentage of the birds colonized with higher levels, then OR might be better.