By Sharon Omahen
University of Georgia
University of Georgia scientists have developed a method for eliminating the harmful E. coli O157:H7 pathogen in cattle watering troughs.
An estimated 73,000 cases of E. coli O157:H7 in humans are reported each year in the United States. Studies have shown that the pathogen can be transferred from one cow to another through the animals' drinking water.
Contaminating drinking water
"Cattle drinking water is often contaminated with cud (rumen content)," said Michael Doyle, a UGA microbiologist and director of the Center for Food Safety in Griffin, Ga. "Cattle water can also have manure in it, and together, this leads to E. coli contamination."
In the past, disinfectants like chlorine have been ineffective at removing E. coli O157:H7 from cattle drinking water. With funding from the American Meat Institute Foundation, Doyle led a project that focused on identifying practical treatments for eliminating E. coli O157:H7 in cattle drinking water.
The UGA scientists first screened various chemicals in search of an effective control.
"We knew right away that chlorine and ozone treatments had little to no effect," Doyle said. "But we were able to ultimately identify two chemical combinations that are highly effective."
Searching for the best control
The best treatments were a combination of lactic acid, acidic calcium sulfate and caprylic acid and another combination of lactic acid, acidic calcium sulfate and butyric acid.
"Both treatments include a base chemical, acidified calcium sulfate, or Safe2O," Doyle said. "This chemical has a very low pH, less than 2, which makes it very acidic."
Doyle's laboratory studies found that the two chemical
formulations not only eliminated E. coli O157:H7, but also killed
other enterohemorrhagic E. coli which are related to
E. coli O157:H7.
But what do the cows think of this new power-drink? UGA animal scientist Joe West fed the treated water to a group of test cows. "We use Calan doors, which are electronically controlled doors," he said. "Each cow has a transponder that works as the door's key."
In this way, West can monitor how much water a cow truly consumes. For the study, he measured how much water the cows drank over seven days and compared that to what they normally drink.
Safer, but not as tasty
He found that the cows drank 19 liters per day of the lactic acid water, compared to 30 liters per day of nontreated water.
"They'll drink the treated water, but obviously, they're reluctant to drink it," he said. "So it's not suited for continuous feeding."
West said cows could survive on the reduced water intake. But when a cow's water or feed intake is reduced, her growth and milk production also decline.
To keep from reducing cows' water intake, the scientists recommend farmers periodically treat their water tanks with the chemical treatment.
"A farmer could treat his tanks for 20 minutes and basically sanitize his watering system," Doyle said. "He could treat the holding tanks and the troughs, then flush and refill them with clean water. This would kill the organism and then provide fresh water for the animals."
Adding the chemical to his cattle's water supply would be an added task and, for now, a voluntary action for the farmer, Doyle said.
Ready when needed
"Until someone down the line gets serious about controlling E. coli at the source, this is just a control method available to farmers," he said. "If on-farm controls should be mandated, we have a treatment available that will work."
Adding the chemicals to cattle drinking water shouldn't be cost-prohibitive for farmers.
"The material is fairly dilute, and we've determined that a very dilute combination can still be effective" Doyle said.
(Sharon Omahen is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)