1a.Objectives (from AD-416):
Identify a “predictor” or “environmental marker” that can be used to determine Salmonella prevalence in feedlot environments and examine the efficacy for the predicting Salmonella prevalence in peripheral lymph nodes.
1b.Approach (from AD-416):
Three feedlots will be identified for sample collection in Texas, Kansas, and Nebraska. Cattle hide and fecal swab samples will be collected (preferably at re-implant) from 4 pens per feedlot, sampling 30% of cattle per pen (target study population: ~200 cattle per feedlot; ~600 total cattle sampled in study). Environmental samples to be collected as possible predictors of Salmonella contamination include: flies, feedlot pen surface material, water troughs, feed, fecal swabs (possible indicator of assymptomatic “Salmonella super shedders”), fecal pats, and hide swabs. At harvest, final fecal swabs and subiliac lymph nodes will be collected from 30% of cattle from study pens.
All samples will be processed for Salmonella enumeration and prevalence.
Study results indicate that high levels of Salmonella contamination on cattle hides are directly related to carcass lymph node contamination. Analysis of feedlot environmental samples including pen surface material, tank water, feed and flies, suggests that high levels of Salmonella in tank water and measureable levels in feed are possible indicators of high levels of Salmonella in a feedlot. Given the ease of collection and processing of these sample types, they may represent good candidates for reliable "predictors" of feedlots that may benefit from a Salmonella intervention.