Microbial pathogens have long been a concern in dairy production because of
their effects on animal health, milk production, and economics.
In 2003, the Agricultural Research Service
entered a partnership with the Regional Dairy Quality Management Alliance to
help validate best management practices (BMPs) that minimize disease risk and
ensure maximum safety of products leaving the farm.
Food safety issues are increasingly prominent in the United States. Thanks
to pasteurization, the risk to consumers of pathogens in milk is very low. But
improper handling of milk and milk products can result in bacterial growth and
substantially increase potential risk to consumers. And there are people who
prefer to consume raw (unpasteurized) milk or raw-milk products.
In 2002, stakeholders in 10 Northeast and Mid-Atlantic states formed the alliance.
Their mission is to ensure a healthy and safe food supply, promote animal health
and welfare, improve productivity and profitability, and encourage environmental
The following year, alliance participants and ARS researchers decided to evaluate
current BMPs and develop new, more effective ones. The collaborative team consists
of ARS's Environmental Microbial Safety Laboratory (EMSL) in Beltsville, Maryland;
ARS's Antimicrobial Research Laboratory in Athens, Georgia; Cornell University;
Pennsylvania State University; and the University of Pennsylvania (UP).
A pilot project, begun in January 2004, consisted of two dairy herdsa
300-cow herd in New York and a 100-cow herd in Pennsylvania. A third herd in
Vermont was recently added.
"These herds were selected on criteria including known Johne's disease
prevalence or Salmonella positive status, Dairy Herd Improvement Association
membership with monthly testing, and on-farm disease recording," says Jo
Ann Van Kessel, an EMSL researcher.
Data collection is the main activity at this time. "We collect biological
sampleslike blood, manure, and bulk tank milkand environmental samples,
such as bird droppings, water, feed, and soil," says Van Kessel.
The biological samples are distributed to university and ARS researchers, who
test them for the presence of Mycobacterium avium subspecies paratuberculosisthe
bacterium that causes Johne's diseaseSalmonella, E. coli O157:H7,
Listeria monocytogenes, and Campylobacter. The samples are also
stored at UP's New Bolton Center biobank to aid future research.
"In one sampling on one of the test farms, we found that although 45 percent
of the cows tested positive for Salmonella, no Salmonella was
actually detected in the bulk tank milk," says ARS microbiologist Jeffrey
Karns. "We're using molecular genetic techniques to detect particular strains
of Salmonella, Listeria, and E. coli. This helps differentiate
those that are harmful to humans from those that are not."
"We'll use the collected data to determine the location of pathogens on
the farms, how they are getting there, how long they survive, and how they get
into milk," says Van Kessel. "We can then look at the BMPs to determine
which ones will truly benefit the dairy farmer."By Sharon
Durham, Agricultural Research Service Information Staff.
This research is part of Food Safety, an ARS National Program (#108) described
on the World Wide Web at www.nps.ars.usda.gov.
Jo Ann Van Kessel and Jeffrey
Karns are with the USDA-ARS Environmental
Microbial Safety Laboratory, 10300 Baltimore Ave., Bldg. 173, Room 201,
Beltsville, MD 20705-2350; phone (301) 504-8287, fax (301) 504-6608.
"ARS Collaborates in Regional Dairy Quality Management Alliance" was published in the April 2005 issue of Agricultural Research magazine.