Cattle explore their environment by licking or chewing nearly everything.

Tapping this natural behavior, University of Nebraska scientists devised an effective, economical way to test pens of cattle for E. coli 0157:H7 – just hang pieces of rope around a pen.

Hang ropes in the evening and within two hours, over half the cattle – plenty for a representative sample – chew them and leave traces of organisms they're carrying. Ropes are removed and specialized lab tests determine E. coli's presence. The bacteria doesn't affect cattle but causes severe illness in humans.

This test grew from ongoing Institute of Agriculture and Natural Resources research on reducing E. coli on farms, feedlots and ranches. Researchers recognized pen testing was important, initially for research and eventually for producers. Individually testing feeder cattle is impractical and expensive.

"The pen is really the unit we're interested in because cattle generally get marketed as pens or groups," explained Veterinary Scientist David Smith, part of the IANR team that developed the test. "This is economical and practical because you don't have to test every animal individually, you look at the whole group."

Smith explored high- and low-tech methods.

"We had some pretty fancy ideas, but the ropes seem to work best. Cattle chew up the rope but it survives, we get good samples and it's disposable."

Research backs the test. Current studies are refining its use and answering practical questions such as how many ropes are needed per pen and how to ship samples for lab testing. Earlier studies revealed when and how to test.

The rope test was the main sampling tool in a large study this summer at five Midwestern feedlots. For the first time, researchers were able to test pens weekly and follow cattle throughout their feedlot period. They also collected composite manure samples from pens.

Their research showed rope tests are more sensitive than manure samples.

Manure samples accurately identify only high prevalence pens where more than 40 percent of cattle are shedding E. coli. Rope tests detect these pens plus medium prevalence pens where at least 16 percent of cattle are shedding the bacteria. Pens where no E. coli is recovered are considered low prevalence; researchers assume it's present at some level.

"Once we analyze all the samples, we'll be able to classify the pens as high, medium or low prevalence," Smith said.

Comparing conditions in high, medium and low prevalence pens, researchers focused on identifying potential E. coli risk factors such as time on feed, temperatures and pen conditions.

"We hope to soon have some more specific risk factors to discuss," Smith said.

Eventually, the rope test should help producers match E. coli intervention strategies to specific pens of cattle. IANR researchers are studying numerous possible interventions.

"This is producer-driven research," Smith said. Producers are eager for specific methods to reduce E. coli's prevalence in feedlots and keep it from reaching processing plants.

Nebraska Legislative Bill 1206, which provides $250,000 annually for five years for NU's E. coli research, and the Nebraska Beef Council fund these studies.

– Vicki Miller