Source:  Tom Johnston, MEATINGPLACE.COM, 11/15/10


Cargill said today it will enter a second stage of testing vaccines intended to reduce E. coli O157:H7 occurrence in cattle, following promising results in the project's first round.

Dan Schaefer, Cargill assistant vice president for beef research and development, told the food and feed safety committee of the United States Animal Health Association in Minneapolis on Sunday that researchers saw a favorable immune-system response to the vaccine and the cattle had no adverse reaction.

"[We] believe there is enough evidence to move forward with a second vaccine trial and anticipate doing so in summer 2011 at a Midwest beef processing facility supplied by mid-size feedlots in the region," Schaefer said, according to a Cargill news release. "We're determining the best way to proceed with this science-based, evolutionary process, which we hope will lead to validating the potential value of vaccine as another food safety tool for beef production."

The first trial in 2010, at a cost of $1 million, entailed vaccination of the entire cattle supply from 10 feedlots dedicated to slaughter at the company's Fort Morgan, Colo., plant from May through August. Of the 85,000 head of cattle, nearly 60,000 head received two doses of the vaccine, one upon arrival at the feedlot and one about 90 days before harvesting. The remaining cattle received a single dose and served as buffers before and after those cycling through the feedlots and that had received two doses.
Buffers allowed Cargill to establish scientific controls to test the effect of whole-feedlot vaccination under commercial conditions.

Replicating the first trial will be a challenge given the number of factors that can potentially influence the effectiveness of a vaccine for reducing E. coli in beef cattle. Among them are weather, geography, seasonality, animal and herd care and management and vaccine dosage.

Moreover, Cargill noted a low level of E. coli O157:H7 in the beef produced at Fort Morgan from the non-vaccinated cattle while vaccinated cattle were being harvested. That, Schaefer said, might influence the significance of the data now being analyzed by independent researchers at Kansas State and Texas Tech universities, the USDA's Meat Animal Research Center and the Beef Checkoff, results of which will likely be available early next year.

They're trying to better understand the meaning and value of the reduction in E. coli in beef from the vaccinated cattle, compared with beef from non-vaccinated animals. This vaccine trial marked the first completed pre-harvest intervention trial that monitored activity from the time of vaccination through measurements in meat.

"The low level of E. coli O157:H7 in the beef from control cattle is something we need to take into consideration when we analyze the data to determine the vaccine's true impact and potential," Schaefer said. "The scientist in me tells me much more research remains to be conducted before we can draw any meaningful conclusions about the long-term efficacy of vaccine use to reduce any strain of bacteria potentially found in beef that could pose health risks to consumers."

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