New research results could be valuable to cattle feeders

Aug 17, 2012

A recently released independent study uncovered some interesting facts about a pair of commercially-available pre-harvest E. coli preventative measures. One of them worked better than previously anticipated and one didn’t seem to work at all.

Kansas State University (K-State) veterinary researchers have recently published the findings of their uniquely real-world relevant study on pre-harvest E. coli treatments. In the study, the researchers tested the efficacy of Pfizer Animal Health’s SRP E. coli vaccine and Nutrition Physiology Corp’s Bovamine direct-fed microbial (DFM) in real world large feedlot settings.

Of greatest note to the commercial cattleman, researchers found the vaccine was exceptionally effective at reducing the prevalence of E. coli shedding in feedlot cattle with only two (rather than the recommended three) vaccinations. And while the DFM did not have any relevant effect on E. coli shedding, it did appear to have slight positive productivity effects.

The study was conducted at a large-scale Nebraska commercial feedlot. Forty pens of an average of 430 head per pen were tested in the roughly 86 days prior to slaughter. A total of 17,148 steers were followed in this project and they weighed an average of 834 pounds at enrollment in the study. They were fed a ration containing 25 percent wet distillers grains and the data collection took place in the summer of 2011, summer being a known time of higher E. coli shedding.

Researchers divided up the study cattle into four different test groups. One randomly assigned group of cattle was the control, receiving neither vaccine nor DFM; one was vaccinated twice during the study period (the product’s recommendations suggests three doses); one was fed the DFM according to label recommendations; and the last group was both vaccinated and fed the DFM. Fecal samples were collected from the pen floors and tested.

The results showed the vaccinated cattle shed E. coli 53 percent less than the control group and vaccinated “high shedders”—those cattle which shed far more E. coli than is the norm—shed 77.3 percent less than control high shedders. These results were found to be highly statistically relevant. This is opposed to the cattle which were given DFM, which showed no statistically relevant reduction in E. coli shedding. Those cattle receiving both preventative measures showed no combined benefit.

The researchers stressed the value of the discovery regarding the two-dose efficiency compared to the recommended three-dose course.

“Showing that level of efficacy with two doses is really important because a shift to two doses from three could significantly cut costs for the beef industry,” said associate professor David Renter, of the study. “In terms of logistics, it can be difficult for commercial feedlot production systems to vaccinate animals three times. Both of these benefits help when considering how the vaccine can be adopted and implemented in the industry.”

The fact that the researchers used a large-scale commercial lot as their testing grounds is a first for this type of research. Many efficiency tests conducted in the past along similar lines have used smaller lots with smaller pen sizes and/or used academic or research lots rather than commercial feedlots. The larger size of the study population and the real world setting and handling procedures during the study contribute to the relevance of the findings, according to the researchers.

“What’s unique about this study is the number of animals we used, the research setting, and that we used commercial products in the way that any cattle producer could use them,” said Renter. “We didn’t want it to be any different than the way somebody would use the products in a commercial feedlot.”

Other benefits of the large size of the study population included a reduced risk of culling or death of subjects during the study damaging results, and allowing for a greater level of confidence when analyzing the data.

The report notes that findings of the DFM’s ineffectiveness are in conflict with prior studies done on the product. The researchers suggested this apparent discrepancy may have been due to their lower dosage and the larger pens used in their study versus the larger doses used on smaller pens of cattle in other studies.

Researchers did, however, point out that DFM-fed cattle saw a slightly improved feed to gain ratio compared to either vaccinated or control cattle. While the improvement was not statistically significant in relation to the DFM, the numbers were close to statistical significance and thereby deserved attention.

“Performance effects need to be further quantified since cattle performance affects beef production costs, and the adoption of pre-harvest control programs will be affected by all costs associated with implementation,” read the report.

The research was funded through a USDA grant, the Agriculture and Food Research Initiative, the National Institute of Food and Agriculture, and K-State. The respective companies provided the necessary products involved in the study. Pfizer provided “unrestricted supplemental funds” for the identification of high shedders and testing samples from such cattle. Neither company was otherwise involved in the study, according to the article’s acknowledgements.

The original article is titled “Efficacy of a vaccine and a direct-fed microbial against fecal shedding of Escherichia coli 0157:H7 in a randomized pen-level field trial of commercial feedlot cattle.” Primary researchers include Charley Cull and David Renter of the K-State College of Veterinary Medicine. The full text of the forprint article can be found for free online as of this printing at, author name search “Cull Renter.”

The SRP vaccine works by stimulating cattle’s immune system to disrupt the ironcollecting abilities of the E. coli cells. E. coli bacteria in the cattle’s gut effectively starve for iron and subsequently cannot reproduce and die. The DFM functions by introducing hardier, beneficial microbes into cattle’s digestive tract which supplant and out-compete harmful bacteria such as E. coli as well as improving the digestive functions of the animal. — Kerry Halladay, WLJ Editor