Dewell, Grant Alan, authorSalman, Mo, advisor2024-03-132024-03-132008https://hdl.handle.net/10217/237685On title page: Spring 2007.Risk factors for prevalence of E. coli O157 prior to slaughter and the genotypic relationship between feedlot and slaughter isolates were investigated. The odds of E. coli O157 positive fecal samples from cattle fed brewers grains were 6 times that for cattle not fed brewers grains. The odds of E. coli O157 positive fecal samples from cattle from Central Nebraska was 9 times that for cattle from Eastern Colorado. Within the sampled pens, 64% of the hide samples at the abattoir corresponded to a feedlot isolate. For carcass samples, 59% of isolates had a corresponding feedlot isolate. Transportation of cattle from the feedlot to the slaughter plant could influence hide contamination of Escherichia coli O157 or Salmonella enterica. Cattle held in E. coli O157 positive lairage pens had eight times greater relative risk of having E. coli O157 positive hide samples compared to cattle held in culture-negative pens. Cattle that were held in lairage pens contaminated with feces had three times greater relative risk for E. coli O157 positive hide samples and twice the relative risk for S. enterica positive hide samples compared to cattle held in clean pens. Cattle that were transported for long distances (> 160.9 km) had twice the relative risk of having E. coli O157 positive hide samples and twice the relative risk of having S. enterica positive hide samples compared to cattle transported shorter distances. Cattle with positive Salmonella enterica hide samples at the feedlot had almost twice the relative risk of having S. enterica positive hide samples compared to cattle without S. enterica positive feedlot hide samples. Cattle transported in trailers with positive S. enterica samples had over twice the relative risk of having S. enterica positive hide samples compared to cattle transported in culture negative trailers. Cattle held off feed longer than 18 hours before loading had a greater relative risk of having S. enterica positive hide samples compared to cattle held off feed for shorter times. Cattle that were agitated during loading had twice the relative risk of having S. enterica positive hide samples compared to cattle that were calm.born digitaldoctoral dissertationsengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.cattleEscherichia coli O157Salmonella entericaanimal sciencesanimal diseasesTextPer the terms of a contractual agreement, all use of this item is limited to the non-commercial use of Colorado State University and its authorized users.