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Pre-Harvest Nutritional Management Strategies to Reduce E. coli O157:H7 and Salmonella spp. Gastrointestinal Survival and Shedding


The meat industry has worked for years to combat the survival of E. coli O157:H7, Salmonella
spp., Campylobacter spp., and other harmful bacteria on meat products by implementing
strategies after harvest to reduce or eliminate such pathogens. Although these strategies have
been successful in reducing the incidence of these pathogens, the likely reason for the presence
of such pathogens on meat products is that these microorganisms are often transiently found in
the gastrointestinal tract of livestock species (Meyer-Broseta et al., 2001; Jay et al., 2005). Thus,
carcass contamination will likely continue to occur unless strategies are developed to reduce the
presence of pathogenic bacteria in the animal itself.
<P> The use of natural feed supplements, such as probiotics [otherwise know as direct-fed microbials
(DFM)] and prebiotics, have been proposed as an alternative to antimicrobial use in livestock.
These compounds have been shown by many researchers to selectively increase populations of
beneficial microorganisms within the rumen which could potentially lead to improvements in
animal performance similar to those seen by ionophores and other feed supplements.
Additionally, through the stimulation of beneficial bacteria, these compounds may be able to
reduce populations of pathogenic microorganisms by out competing pathogens for nutrients and
places of attachment within the gastrointestinal tract.
<P> The objective of this study was to evaluate the efficacy of two natural feed supplements to
reduce the survival and subsequent shedding of E. coli O157:H7 and Salmonella spp. in fed
cattle during finishing and immediately prior to harvest.

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Findings: The addition of AMF or LEV to the diet of feedlot steers did not have an impact on the fecal shedding of E. coli O157:H7 throughout the finishing period. However, differences in the shedding of E. coli O157:H7 by feedlot cattle were observed between the two corn sources fed in the study. The percent of animals with a pen shedding E. coli O157:H7 for pens receiving HMC was significantly less than the prevalence of E. coli O157:H7 among pens fed DWSC. Additionally, steers fed HMC shed E. coli O157:H7 less frequently than steers fed DWSC, indicating that these animals may be less susceptible to infection.
<P> No animals tested positive for Salmonella throughout the feeding period, therefore, the effects of the two corn types or the feeds supplements on the fecal excretion of Salmonella spp. could not be determined. However, this is an indication that the prevalence of Salmonella spp. among feedlot cattle is low. Addition of AMF or LEV to the diet of feedlot steers did not have a negative impact on growth performance or carcass characteristics. In fact, AMF improved feed efficiency by 7% when added to the DWSC diet.
<P> Neither AMF nor LEV was able to reduce the fecal shedding of E. coli O157:H7 by feedlot cattle. However, this study provided evidence that cattle being finished on a high concentrate diet that utilizes high-moisture corn may be more resilient and have a lower level of susceptibility to infection from E. coli O157:H7 than those cattle being finished on a high concentrate diet formulated with dry, whole shelled corn. This is a beneficial finding for producers as the feeding of HMC tends to improve average daily gain in steers without increasing feed consumption compared to steers fed DWSC. Therefore, feeding HMC may reduce the prevalence of E. coli O157:H7 in feedlot steers, while also leading to an improvement in feed efficiency and profitability.

<P> For complete projects details, view the <a href="…; target="_blank">Project Summary. </a>

Zerby, Henry
Ohio State University
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