New Safety Approach for Dairy Cattle

Adding chlorine to trough water effectively reduces survival of the bacterium that causes Johne’s disease among dairy cattle—especially if the trough is made of stainless steel, according to a new study.

“Chlorine is a cost-effective, readily available disinfectant, and trough chlorination should be easy to implement in an agricultural environment,” said Kimberly Cook, PhD, a microbiologist at the U.S. Department of Agriculture (USDA) Agricultural Research Service, Animal Waste Management Research Unit, in Bowling Green, Ky. Dr. Cook was first author of a paper describing the study (Cook KL, Britt JS, Bolster CH. Vet Microbiol. 2010;141(1-2):103-109).

Dr. Cook and colleagues evaluated the hidden sources of contamination where animals may be exposed to Mycobacterium avium subspecies paratuberculosis (Map), the agent that causes Johne’s disease. Trough basins are not only a moist and nutrient-rich environment for the bacterium, but they also provide a surface for biofilm formation, she said in an e-mail to Food Quality.

The researchers evaluated Map’s ability to form biofilms on four watering trough materials: concrete, plastic, stainless steel, and galvanized steel. The study also looked at the bacterium’s ability to persist in the microbial flora within the trough water and to become part of the biofilm on the trough.

“Our research findings suggest that trough materials provide a ready source for biofilm formation,” she said. “Biofilms rapidly formed (within three days) and persisted for over 300 days, suggesting that M. paratuberculosis [Map] attaches to trough sides where nutrients are readily available and where it is protected from other microorganisms and from washout.”

Stainless steel troughs had the lowest concentration of Map survival, followed by plastic, galvanized steel, and concrete.

The weekly addition of two parts per million of chlorine to the trough water reduced survival of Map on stainless and galvanized steel troughs but not on the plastic or concrete troughs. “Regardless of trough material, the best advice would be to clean troughs routinely to minimize sediment and biofilm formation and improve chlorine effectiveness,” Dr. Cook said.