ARS | Publication request: Influence of body condition and forage type on prevalence of Escherichia coli O157:H7 and Salmonella in grazing beef cattle.

Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 23, 2009
Publication Date: August 10, 2009
Citation: Looper, M.L., Edrington, T.S., Rosenkrans, C.F. 2009. Influence of body condition and forage type on prevalence of Escherichia coli O157:H7 and Salmonella in grazing beef cattle. Letters in Applied Microbiology. 49:361-365.

Interpretive Summary: E. coli and Salmonella cause approximately 76 million foodborne illnesses and about 5,000 deaths annually in the U.S. Changes in forage type and nutritional status of an animal may influence fecal shedding of pathogenic bacteria; however, the combination of both of these factors on fecal shedding of pathogens from grazing cows is non-existent. ARS scientists from Booneville, AR, and College Station, TX, and personnel from the University of Arkansas conducted a study to determine the effects of forage type and body condition (cow’s relative fatness) on the prevalence of fecal shedding of E. coli O157:H7 and Salmonella from cows. Fecal samples were collected at d 0, 30 and 62 of the experiment from cows in thin or moderate body condition score grazing either common bermudagrass (CB) or toxic endophyte-infected (EI) tall fescue. Overall, percentage of fecal samples positive for E. coli O157:H7 was 2.6% and 2.0% for Salmonella. Consumption of either toxic EI fescue or CB forages did not influence shedding of either E. coli O157:H7 or Salmonella in cows. Further, fecal shedding of pathogenic bacteria was not altered by BC of cows and loss of BC in moderate BC cows did not influence fecal shedding of pathogenic bacteria. This information is of interest to livestock producers, extension personnel, and agricultural professionals who advise producers on food safety issues and livestock management practices.

Technical Abstract: Multiparous Brahman-influenced cows were managed to achieve thin body condition score (BCS = 4.5 +/- 0.1; n = 50) or moderate (BCS = 6.6 +/- 0.1; n = 65) body condition (BC) to determine the influence of forage type on the prevalence of fecal shedding of E. coli O157:H7 and Salmonella. Cows within each BC were randomly assigned to graze either common bermudagrass (CB; n = 3 pastures) or toxic endophyte-infected (EI) tall fescue (n = 3 pastures) during a 62-d period. Fecal samples were collected at d 0, 30 and 62 of the experiment. Percentage of fecal samples positive for E. coli O157:H7 was 2.6% and 2.0% for Salmonella. Main effect of forage type did not influence the prevalence of E. coli O157:H7 (P = 0.35) or Salmonella (P = 0.66). Similar to forage type, the main effect of BC did not influence the prevalence of E. coli O157:H7 (P = 0.45) or Salmonella (P = 0.99) in the feces of cows. Interaction of BC and forage type did not alter (P greater than 0.10) prevalence of E. coli O157:H7 or Salmonella in the feces of postpartum Brahman-influenced cows. Consumption of either toxic EI fescue or CB forages did not influence shedding of either E. coli O157:H7 or Salmonella in Brahman-influenced cows in the current study. Further, fecal shedding of pathogenic bacteria was not altered by BC of cows and loss of BC in moderate BC cows did not influence fecal shedding of pathogenic bacteria. Increased frequency of fecal collection and (or) use of ruminants inoculated with pathogenic bacteria should be the basis of future studies investigating the effects of body condition and (or) forage diet on fecal shedding of E. coli O157:H7 and Salmonella.