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United States Department of Agriculture

Agricultural Research Service

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Research Project: Salmonella in the Peripheral Lymph Nodes of Cattle: Investigation into the Regional and Seasonal Variation in Feedlot Cattle ...

Location: Food and Feed Safety Research

2013 Annual Report


1a.Objectives (from AD-416):
Investigate the potential explanations for the seasonal and regional differences in lymph node prevalence of Salmonella in feedlot cattle, and elucidate the factors responsible for the differences observed in lymph node prevalence of Salmonella between fed beef and dairy cattle within the Southwest United States.


1b.Approach (from AD-416):
Seasonal/Regional Feedlot Collections: Using a soil temperature map, we will identify feedlots within 3 or 4 of the ground temperature zones (TX, OK, or KS, and NE) and sample two feedlots/zones during the summer and fall months (June through October). Numerous samples/observations will be collected on each feedlot visit, including: pen fecal pats (4 pens/feedlot; representing 30% of cattle within each pen), hide swabs, feed and water samples, pen soil samples and soil temperature, flies and other insects, fly burden, ambient temperature, humidity, and precipitation. Samples will be cultured for Salmonella and isolates serogrouped. Dairy versus Feedlot Collections: Two feedlots (preferably with a known high peripheral lymph node prevalence of Salmonella) and four dairies (two vaccinateed for Salmonella and two non-vaccinated herds), all located within a 100-mile radius in the Southwestern United States will be utilized in the proposed research. All dairies and feedlots will be sampled monthly (June through November) during the same week. Numerous samples/ observations will be collected at each location on each visit including: pen fecal pats (4 pens/operation; representing 30% of cattle within each pen), hide swabs, feed and water samples, pen soil samples and soil temperature, flies and other insects, fly burden, ambient temperature, humidity, and precipitation. Samples will be cultured for Salmonella and isolates serogrouped.


3.Progress Report:

This is a new project, with the goal to further our understanding of Salmonella uptake by the peripheral lymph nodes of cattle and to evaluate if certain classes of cattle are more likely to have Salmonella-positive lymph nodes. In FY 2013, definition of project scope was achieved and relevant protocols were finalized. As work under this project progresses, a more detailed and thorough understanding of the factors responsible for Salmonella acquisition by the peripheral lymph nodes will be obtained. The work will define differences due to cattle breed (Holstein versus beef breeds) and type (cull dairy versus cull beef versus fed beef), utilizing samples collected on the farm as well as lymph nodes at slaughter. Results of this work will not only increase our understanding of Salmonella transmission and reservoirs, but will also determine which cattle types are at greatest risk.


Last Modified: 9/21/2014
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