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Q: I have heard that distillers' grains increases the number of cattle testing positive for E. coli O157:H7. What E. coli O157:H7 interventions are available for beef cattle producers today?

A: First, it is important to note that the entire body of research is inconclusive on the impact of distillers' grains on E. coli O157:H7 shedding in cattle, and there is some evidence that distillers' grains levels commonly fed in finishing diets today may actually reduce E. coli O157:H7 shedding in some cases. However, the widespread use of preharvest E. coli O157:H7 interventions would be beneficial for the overall industry from the standpoints of public perception, safe food production, and ethics. There are several pre-harvest E. coli O157:H7 interventions currently available on the market that work well, and some that are in the process of getting approval for use to reduce the number of cattle testing positive for E. coli O157:H7. Most recently E. coli vaccines have been given conditional approval for the prevention of E. coli O157:H7 shedding. Several studies have proven the efficacy of vaccines in reducing the number of cattle testing positive for E. coli O157:H7. However, they require cattle to be vaccinated three times during the feeding period, which can pose labor issues and reduced intakes due to vaccination if the cattle are pulled out of their pen solely for the purpose of vaccinating for E. coli. Because no improvement in performance has been observed with E. coli vaccines, all vaccination costs fall on the producer. These costs include the cost of the vaccine, the cost of labor to revaccinate, and potential reductions in performance associated with reduced intakes from pulling cattle out of the pen to revaccinate. Several studies have shown that fewer cattle fed direct-fed microbials such as Lactobacillus acidophilus test positive for E. coli O157:H7 shedding, but one needs to be careful in interpretation of the data. The precise strains and doses need to be considered when evaluating any direct-fed microbial product used for any purpose. Vast differences exist among bacteria even within the same species. You may be surprised to find out that E. coli is the primary facultative organism of the human gastrointestinal tract and can be very beneficial to humans. However, the O157:H7 strain (i.e. E. coli O157:H7) is a pathogen that may be found in uncooked ground hamburger that produces a Shiga toxin that can cause a severe immune response in humans and in some cases results in death. Therefore, vast differences exist between strains within all bacterial species and one cannot assume that because cattle fed one strain of Lactobacillus acidophilus shed less E. coli O157:H7, that this would be true for cattle fed any strain of Lactobacillus acidophilus. Furthermore, research suggests that the cattle fed Lactobacillus acidophilus shed less E. coli O157:H7 in a dose-dependent manner. In other words, some studies indicate that cattle fed more Lactobacillus acidophilus are less likely to shed E. coli O157:H7 than cattle fed lower doses of Lactobacillus acidophilus of the same strain. Therefore you should make certain that strain and dose in any direct-fed microbial product has been researched for its intended purpose.